Chapter 9: Energy in a Cell...Section 9.1 BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES Use with Chapter 9, Section 9.1 How is each of these organisms using energy? In

Activities/FeaturesObjectivesSection

Chapter 9 OrganizerChapter 9 Organizer

ATP in a MoleculeNational Science EducationStandards UCP.2, UCP.3;A.1, A.2; B.3, B.6; C.1, C.5(1 session, 1/2 block)

Photosynthesis:Trapping the Sun’sEnergyNational Science EducationStandards UCP.2, UCP.3;A.1, A.2; B.3, B.6; C.1, C.5;G.1 (2 sessions, 1 block)

Getting Energy toMake ATPNational Science EducationStandards UCP.1-3; A.1,A.2; B.3, B.6; C.1, C.5; F.6(3 sessions, 1/2 block)

1. Explain why organisms need a supply ofenergy.

2. Describe how energy is stored andreleased by ATP.

3. Relate the structure of chloroplasts tothe events in photosynthesis.

4. Describe light-dependent reactions.5. Explain the reactions and products of

the light-independent Calvin cycle.

6. Compare and contrast cellular respira-tion and fermentation.

7. Explain how cells obtain energy fromcellular respiration.

Problem-Solving Lab 9-1, p. 228

Problem-Solving Lab 9-2, p. 232MiniLab 9-1: Use Isotopes to UnderstandPhotosynthesis, p. 234Inside Story: The Calvin Cycle, p. 235Careers in Biology: Biochemist, p. 236Internet BioLab: What factors influencephotosynthesis? p. 244Chemistry Connection: Plant Pigments, p. 246

Inside Story: The Citric Acid Cycle, p. 239Problem-Solving Lab 9-3, p. 241MiniLab 9-2: Determine if Apple JuiceFerments, p. 242

MATERIALS LIST

BioLabp. 244 1000 mL beaker, Elodea plants(3), string, washers, colored cellophane,150-watt light with reflector, 0.25%baking soda solution, watch with sec-ond hand

MiniLabsp. 234 clay (various colors)p. 242 small beaker, plastic pipette,large test tube, water, metal washers,baker’s yeast, apple juice

Alternative Labp. 240 black paper, labels, iodine solu-tion, paper clips, hot plate, beaker,95% ethanol, small bowl, Coleus plants

Quick Demosp. 229 potato, water, beaker, Bunsenburnerp. 233 prismp. 238 sugar (sucrose), water, flask,baker’s yeastp. 251 potato, meat, vegetable oil,molecular model of lipid

Need Materials? Contact Carolina Biological Supply Company at 1-800-334-5551or at http://www.carolina.com

Products Available FromGlencoeTo order the following products,call Glencoe at 1-800-334-7344:CD-ROMsNGS PictureShow: The CellNGS PictureShow: Plants: WhatIt Means to Be GreenCurriculum KitGeoKit: Cells andMicroorganisms Transparency SetsNGS PicturePack: The CellNGS PicturePack: Plants: What ItMeans to Be Green

Products Available FromNational Geographic SocietyTo order the following products,call National Geographic Societyat 1-800-368-2728:VideoDiscovering the CellPhotosynthesis: Life Energy

Index to NationalGeographic MagazineThe following articles may beused for research relating to thischapter:“How the Sun Gives Life to theSea,” by Paul A. Zahl, February1961.

Teacher’s Corner

226B226A

Energy in a CellEnergy in a Cell

TransparenciesReproducible MastersSection

ATP in a Molecule

Photosynthesis:Trapping theSun’s Energy

Getting Energy to Make ATP

Section 9.1

Section 9.2

Section 9.3

Teacher Classroom Resources

Reinforcement and Study Guide, p. 37Tech Prep Applications, pp. 15-16Content Mastery, pp. 41-42, 44

Reinforcement and Study Guide, p. 38-39Concept Mapping, p. 9Critical Thinking/Problem Solving, p. 9BioLab and MiniLab Worksheets, p. 39 Content Mastery, pp. 41, 43-44

Reinforcement and Study Guide, p. 40BioLab and MiniLab Worksheets, pp. 40-42Laboratory Manual, pp. 61-68Content Mastery, pp. 41, 43-44 L1

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Section Focus Transparency 21Basic Concepts Transparency 11

Section Focus Transparency 22Basic Concepts Transparency 12

Section Focus Transparency 23Basic Concepts Transparency 13Reteaching Skills Transparency 14Reteaching Skills Transparency 15

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Assessment Resources Additional ResourcesSpanish ResourcesEnglish/Spanish AudiocassettesCooperative Learning in the Science ClassroomLesson Plans/Block Scheduling

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Chapter Assessment, pp. 49-54MindJogger VideoquizzesPerformance Assessment in the Biology ClassroomAlternate Assessment in the Science ClassroomComputer Test BankBDOL Interactive CD-ROM, Chapter 9 quiz

Section 9.2

Section 9.1

Section 9.3

Refer to pages 4T-5T of the Teacher Guide for an explanation of the National Science Education Standards correlations.

Key to Teaching StrategiesKey to Teaching Strategies

Level 1 activities should be appropriatefor students with learning difficulties.Level 2 activities should be within theability range of all students.Level 3 activities are designed for above-average students.ELL activities should be within the abilityrange of English Language Learners.

Cooperative Learning activitiesare designed for small group work.These strategies represent student prod-ucts that can be placed into a best-workportfolio.These strategies are useful in a blockscheduling format.

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The following multimedia resources are available from Glencoe.

Biology: The Dynamics of LifeCD-ROM

Animation: The Light ReactionsExploration: Parts of the CellExploration: Phases of MitosisBioQuest: Cellular Pursuit

Videodisc ProgramThe Light Reactions

The Infinite VoyageUnseen WorldThe Champion Within

The Secret of Life SeriesATP StructureATP FunctionATP Serves as an Energy Carrier

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http://www.carolina.com

Section

Cell EnergyEnergy is essential to life. All liv-

ing organisms must be able to pro-duce energy from the environment inwhich they live, store energy forfuture use, and use energy in a con-trolled manner.

Work and the need for energyYou’ve learned about several cell

processes that require energy. Activetransport, cell division, movement offlagella or cilia, and the productionand storage of proteins are someexamples. The transport of proteins isshown in Figure 9.1. You can proba-bly come up with other examples ofbiological work, such as muscles contracting during exercise, yourheart pumping, and your brain

9.1 ATP IN A MOLECULE 227

spring stores energy when it iscompressed. When the compressedspring is released, energy is also

released, energy that sends this smiley-face toy flying into the air. Like this coiledspring, chemical bonds store energy thatcan be released when the bond is broken.Just as some springs are tighter than others, some chemical bonds store more energy than others.

SECTION PREVIEW

ObjectivesExplain why organismsneed a supply ofenergy.Describe how energy isstored and released byATP.

VocabularyATP (adenosine

triphosphate)ADP (adenosine

diphosphate)

9.1 ATP in a Molecule

Stored energyFigure 9.1 Active transportrequires energy tobind and pump thismolecule across theplasma membrane.

Carrier protein shown withtwo binding sites.

AA A molecule binds to thecarrier protein.

BB

Energy released as a phos-phate group from ATP istransferred to the protein.

CC The phosphate group andenergy trigger the proteinto pump the moleculethrough the membrane.

DD

P i i i h b S ifi l bi d

ATP (ADP)

h h i f d d i h h

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Section 9.1

BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES

Use with Chapter 9,Section 9.1

How is each of these organisms using energy?

In what other ways do organisms use energy?

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Transparency Using Energy21 SECTION FOCUS

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PrepareKey ConceptsStudents will examine the sourceof cellular energy—the ATP mol-ecule. They will also learn aboutthe processes in which cells usethe energy stored in ATP.

Planning■ Obtain a potato, peanuts, a

dissection needle, a cork, and aBunsen burner for the QuickDemo and closing Demon-stration.

■ Gather toothpicks, gumdrops,and construction paper for themodeling activities.

1 FocusBellringer Before presenting the lesson,display Section Focus Trans-parency 21 on the overhead pro-jector and have students answerthe accompanying questions.

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Assessment PlannerAssessment PlannerPortfolio Assessment

Assessment, TWE, p. 243BioLab, TWE, pp. 244-245

Performance AssessmentProblem-Solving Lab, TWE, pp. 228, 232MiniLab, TWE, p. 242Assessment, TWE, p. 236Alternative Lab, TWE, pp. 240-241MiniLab, SE, pp. 234, 242BioLab, SE, pp. 244-245

Knowledge AssessmentAssessment, TWE, pp. 229, 230MiniLab, TWE, p. 234Section Assessment, SE, pp. 230, 236, 243Chapter Assessment, SE, pp. 247-249

Skill AssessmentAssessment, TWE, pp. 233, 240Problem-Solving Lab, TWE, p. 241

226 ENERGY IN A CELL

Energy in a Cell

What You’ll Learn■ You will learn what ATP is.■ You will explain how ATP

provides energy for the cell.■ You will describe how chloro-

plasts trap the sun’s energy tomake ATP and complex car-bohydrates.

■ You will compare ATP pro-duction in mitochondria andchloroplasts.

Why It’s ImportantEvery cell in your body needsenergy in order to function.The energy your cells produceand store is the fuel for basicbody functions such as eatingand breathing.

The Source of EnergyWatch your teacher’s move-ments as he or she conducts theclass. Where does the energyfor this activity come from?

To find outmore about

how cells use and produceenergy, visit the GlencoeScience Web Site. www.glencoe.com/sec/science

9

GETTING STARTEDGETTING STARTED

ChapterChapter

Energy can be capturedthrough photosynthesis in these cabbage leaves,or burned into electricityat this power plant.

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Theme DevelopmentThe main theme of this chapteris energy. ATP is presented asthe energy storage molecule andthe most prevalent source ofenergy for cells. Both the synthe-sis and breakdown of ATP arecovered. An underlying theme isthat there is cellular unity withindiversity. All cells carry out res-piration and many cells also carryout photosynthesis.

Chapter 9Chapter 9

MultipleLearningStyles

Look for the following logos for strategies that emphasize different learning modalities.

Kinesthetic Portfolio, p. 228;Reteach, p. 230; Project, p. 233Visual-Spatial Portfolio, p. 239;Check for Understanding, p. 243Interpersonal Portfolio, p. 232;

Intrapersonal Meeting IndividualNeeds, pp. 229, 238; Extension,

p. 236

Linguistic Biology Journal, pp. 229, 234; Extension,

p. 230; Meeting Individual Needs, p. 231

GETTING STARTED DEMOGETTING STARTED DEMO

Bring out play money in sev-eral size bills—$1, $10, $50,and $100. Have students pointout expensive and inexpensiveobjects. Relate the cost ofgoods to the energy needsrequired by an ant to lift andmove a crumb. Point out thatsometimes a lot of energymust be broken down intosmaller amounts, just as a $100bill must be broken down tomake change for a smallerpurchase.

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If time does not permit teach-ing the entire chapter, use theBioDigest at the end of theunit as an overview.

Resource ManagerResource Manager

Section Focus Transparency 21and Master

Basic Concepts Transparency11 and Master

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http://www.glencoe.com/sec/science

ATP by bonding with another phos-phate group. This creates a renew-able cycle of ATP formation andbreakdown. Figure 9.2 illustrates thechemical reactions that are involvedin the cycle.

The formation/breakdown recy-cling activity is important because itrelieves the cell of having to store allof the ATP it needs. As long as phos-phate molecules are available, the cellhas an unlimited supply of energy.Another benefit of the formation/breakdown cycle is that ADP canalso be used as an energy source.Although most cell functions requirethe amount of energy in ATP, somecell functions do not require as muchenergy and can use the energy storedin ADP.

How cells tap into the energystored in ATP

When ATP is broken down andthe energy is released, cells must havea way to capture that energy and useit efficiently. Otherwise, it is wasted.ATP is a small compound. Cellularproteins have a specific site whereATP can bind. Then, when the phos-phate bond is broken and the energyreleased, the cell can use the energyfor activities such as making a proteinor transporting molecules throughthe plasma membrane. This cellularprocess is similar to the way energyin batteries is used by a radio.Batteries sitting on a table are of littleuse if the energy stored within thebatteries cannot be accessed. Whenthe batteries are snapped into theholder on the radio, the radio thenhas access to the stored energy andcan use it. Likewise, when the energyin the batteries has been used, thebatteries can be taken out, recharged,and replaced in the holder. In a simi-lar fashion in a cell, when ATP hasbeen broken down to ADP, ADP is

9.1 ATP IN A MOLECULE 229

+

+

energy released

Adenosine moleculeP P P

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Adenosine P P

Adenosine triphosphate (ATP)

Adenosine diphosphate (ADP) phosphorylatedmolecule

Figure 9.2The addition and release of a phosphate group on adenosine diphosphate creates a cycle of ATP formation and breakdown.

energy

ADP

ADP

ATP

Figure 9.3To access the energy stored in ATP, proteins bind ATP and allow the phosphate group to be released. The ADP that is formed isreleased, and the protein binding site can once again bind ATP.

released from the binding site in theprotein and the binding site may thenbe filled by another ATP molecule.ATP binding and energy release in aprotein is shown in Figure 9.3.

229

Knowledge Have studentsexplain in their own words howenergy is stored within an ATPmolecule. L2

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AssessmentAssessment

Why is fat the choice?Humans store their excess energy as fat rather than as carbohydrates. Why is this? From an evolutionary and efficiency point of view, fats are better for storage than carbohydrates. Find out why.

AnalysisThe following facts

compare certain characteris-tics of fats and carbohydrates:A. When broken down by the body, each six-carbon mole-

cule of fat yields 51 ATP molecules. Each six-carbon carbo-hydrate molecule yields 38 ATP molecules.

B. Carbohydrates bind and store water. The metabolism ofwater yields zero ATP. Fat has zero grams of water boundto it.

C. An adult who weighs 70 kg can survive on the energyderived from stored fat for 30 days without eating. Thesame person would have to weigh nearly 140 kg to sur-vive 30 days on stored carbohydrates.

Thinking Critically1. From an ATP production viewpoint, use fact B to make a

statement regarding the efficiency of fats vs. carbohy-drates.

2. Explain why the average weight for humans is close to 70 kg and not 140 kg.

Problem-Solving Lab 9-1Problem-Solving Lab 9-1 Recognizing Causeand Effect

controlling your entire body. Thiswork cannot be done without energy.Read the Problem-Solving Lab on thispage and think about how the humanbody stores energy.

When you finish strenuous physi-cal exercise, such as running crosscountry, your body wants a quicksource of energy, so you may eat acandy bar. Similarly, there is a mole-cule in your cells that is a quicksource of energy for any organelle inthe cell that needs it. This energy isstored in the chemical bonds of themolecule and can be used quickly andeasily by the cell.

The name of this energy moleculeis adenosine triphosphate (uh DEN

uh seen • tri FAHS fayt), or ATP forshort. ATP is composed of an adeno-sine molecule with three phosphategroups attached. Recall that phos-phate groups are charged molecules,and remember that molecules withthe same charge do not like being tooclose to each other.

Forming and Breaking Down ATP

The charged phosphate groups actlike the positive poles of two mag-nets. If like poles of a magnet areplaced next to each other, it is diffi-cult to force the magnets together.Likewise, bonding phosphate groupsto adenosine requires considerableenergy. When only one phosphategroup is attached, a small amount ofenergy is required and the chemicalbond does not store much energy. A molecule of this sort is calledadenosine monophosphate (AMP).When a second phosphate is added, a more substantial amount of energyis required to force the two phos-phate groups together. A molecule of this sort is called adenosinediphosphate, or ADP. When thethird phosphate group is added, atremendous amount of energy isrequired to force the third chargedphosphate close to the two otherphosphate groups. The third phos-phate group is so eager to get awayfrom the other two that, when thatbond is broken, a great amount ofenergy is released.

The energy of ATP becomes avail-able when the molecule is brokendown. In other words, when thechemical bond between phosphategroups in ATP is broken, energy isreleased and the resulting molecule isADP. At this point, ADP can reform


OriginWORDWORD

mono-, di-, triFrom the Latinwords mono, di, andtri, meaning “one,”“two,” and “three,”respectively.Adenosine triphos-phate contains threephosphate groups.

228

2 Teach

Purpose Students will determine that fat,rather than carbohydrates, is thepreferred compound for energystorage in humans.

Process Skillsacquire information, compareand contrast, think critically,draw a conclusion

BackgroundFats yield more ATPs than carbo-hydrates because they have moreC–H bonds. A six-carbon fatfragment has a molecular weightof about 100, while the same carbohydrate size has a molecularweight of 180. Fats are hydro-phobic while carbohydrates arehydrophilic.

Teaching Strategies■ Emphasize that this lab dis-cusses the storage of excessenergy and reiterate that carbo-hydrates are also important com-pounds.■ Elicit from students if theybelieve early humans were typi-cally very agile. Heavy body weightwould not have been an asset to thesurvival of hunters. Therefore, ifearly humans were storing energy asfat, they were not likely very agile.

Thinking Critically

1. Because the metabolism ofwater yields zero ATP, wateris “excess baggage.” Fat, withno water, carries less “excessbaggage,” helping to make itmore efficient.

2. Because we store excessenergy as fat, we do not carrythe weight of water that isassociated with carbohy-drates.

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Problem-Solving Lab 9-1Problem-Solving Lab 9-1

PortfolioPortfolio

Modeling Chemical CompoundsKinesthetic Provide students withtoothpicks and gumdrops of differ-

ent sizes and colors. Have them use thematerials to make models of ATP and ADP.Have students include in their portfolios adescription of how the molecules differfrom each other and how these differ-ences relate to energy.

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MEETING INDIVIDUAL NEEDS MEETING INDIVIDUAL NEEDS

Hearing ImpairedIntrapersonal Give hearing im-paired students a photograph of

an organism from a magazine or similarsource and ask them to list the activitiesof the organism that require energyfrom ATP.

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Quick DemoQuick Demo

To demonstrate the transferof energy in small amounts,heat a potato in boiling wateror in a microwave oven in theschool cafeteria. When it iscool enough to handle safely,have students pass the heatedpotato to one another. Askstudents who first handle thepotato to describe its temper-ature as hot, warm, cool, orcold. Have a student near theend make the same observa-tion.

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BIOLOGY JOURNAL BIOLOGY JOURNAL

Surviving Without Bread orWater

Linguistic Have students find outhow long a person can survive with-

out food and without water. Have stu-dents report their findings and evaluatewhy people perish without water beforethey perish without food.

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Performance Have students researchwhere fat is stored within the human body,including any differences between male andfemale. Have students write three questionsabout what they have learned. Use thePerformance Task Assessment List forAsking Questions in PASC, p. 19. L3

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VIDEODISCThe Secret of LifeATP Structure

ATP Function

!7;:$H"

!7;:.I"ATP Serves as an Energy Carrier

!7;:8J"


Reinforcement and StudyGuide, p. 37

Content Mastery, p. 42Tech Prep Applications, p. 15

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Section AssessmentSection Assessment

Understanding Main Ideas1. What processes in the cell need energy from ATP?2. How does ATP store energy?3. How can ADP be “recycled” to form ATP again?4. How do proteins in your cells access the energy

stored in ATP?

Thinking Critically5. Phosphate groups in ATP repel each

other because they have negative charges.

What charge might be present in the ATP binding site of proteins to attract another ATPmolecule?

6. Observing and Inferring When animals shiverin the cold, muscles move almost uncontrollably.Suggest how shivering helps an animal survive inthe cold. For more help, refer to ThinkingCritically in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

Uses of Cell EnergyYou can probably think of hun-

dreds of physical activities thatrequire energy, but energy is equallyimportant at the cellular level fornearly all of the cell’s activities.

Making new molecules is one waythat cells use energy. Some of thesemolecules are enzymes, which carry

out chemical reactions. Other mole-cules build membranes and cellorganelles. Cells use energy to main-tain homeostasis. Kidneys use energyto move molecules and ions in orderto eliminate waste substances whilekeeping needed substances in thebloodstream. Figure 9.4 shows sev-eral organisms and activities thatillustrate ways that cells use energy.


Figure 9.4ATP fuels the cellular activity thatdrives the organism.

Nerve cells transmitimpulses by using ATP topower the active trans-port of certain ions.

AA

Fireflies, some caterpillars, such asthe one shown here, and manymarine organisms produce light bya process called bioluminescence.The light results from a chemicalreaction that is powered by thebreakdown of ATP.

CC

Some organismswith cilia or flagella(left) use energyfrom ATP to move.

BB

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3 AssessCheck for UnderstandingAsk students why energy must bestored in small amounts andrelate the answer to paying for asmall purchase with a $1 billrather than with a $50 bill.

ReteachKinesthetic Have studentsjoin like poles of four small

magnets to simulate the storageof energy in ATP. Explain howenergy is released when the mag-nets are pulled apart.

ExtensionLinguistic Have interestedstudents write a report

about a bioluminescent organismand include facts about thatorganism’s energy requirements.

Knowledge Ask studentsto summarize how each organismor structure in Figure 9.4 usesenergy.

4 CloseDemonstrationBurn a peanut to demonstratethat energy is stored in food.Impale a peanut on the end of adissection needle. Stick the otherend of the needle into a cork.Ignite the peanut with a Bunsenburner. Ask students to describethe form of energy released dur-ing burning. Energy is released aslight and heat.

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Section AssessmentSection AssessmentSection Assessment1. Active transport, movement and protein

synthesis are examples.2. ATP stores energy in its phosphate–phos-

phate bonds.3. A phosphate group can be added to ADP,

reforming ATP.4. They may have a pocket that ATP will fit

into so that when ATP releases energy,the protein can use it.

5. Opposite charges attract, so an ATP bind-ing site might have a positive charge.

6. When muscles move during shivering,heat is generated. This heat helps towarm the animal.

Section

Trapping Energy fromSunlight

To use the energy of the sun’slight, plant cells must trap lightenergy and store it in a form that isreadily usable by cell organelles—that form is ATP. However, lightenergy is not available 24 hours a day,so the plant cell must also store someof the energy for the dark hours.Photosynthesis is the process plantsuse to trap the sun’s energy and buildcarbohydrates, called glucose, thatstore energy. To accomplish this, pho-tosynthesis happens in two phases.The light-dependent reactionsconvert light energy into chemicalenergy. The molecules of ATP

produced in the light-dependentreactions are then used to fuel thelight-independent reactions thatproduce glucose. The general equa-tion for photosynthesis is written as follows:

6CO2 + 6H2O ➜ C6H12O6 + 6O2

The BioLab at the end of this chap-ter describes an experiment you canperform to investigate the rate ofphotosynthesis.

The chloroplast and pigmentsRecall that the chloroplast is the

cell organelle where photosynthesisoccurs. It is in the membranes of thethylakoid discs in chloroplasts that thelight-dependent reactions take place.

9.2 PHOTOSYNTHESIS: TRAPPING THE SUN’S ENERGY 231

Have you ever admired a beau-tiful rainbow shimmering inthe air after a rainstorm? You

may not have realized that the colorsyou saw represent the sun’s energybroken into different wavelengths,which our eyes interpret as color. Toleaves on a tree, the wavelengths of light represent a source of energy to be stored and used.

SECTION PREVIEW

ObjectivesRelate the structure of chloroplasts to theevents in photosynthesis.Describe the light-dependent reactions.Explain the reactionsand products of thelight-independentCalvin cycle.

Vocabularyphotosynthesislight-dependent

reactionslight-independent

reactionspigmentschlorophyllelectron transport chainNADP+photolysisCalvin cycle

9.2 Photosynthesis: Trappingthe Sun’s Energy

Photosynthesisrequires sunlight.

OriginWORDWORD

photosynthesisFrom the Greekwords photo, mean-ing “light,” and syn-tithenai, meaning“to put together.”Photosynthesis putstogether sugar mol-ecules using energyfrom light, water,and carbon dioxide.

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Section 9.2

PrepareKey ConceptsStudents will relate the structureof the chloroplast to the processof photosynthesis. They will alsoexplore the overall reactions thatoccur in the light reactions andthe Calvin cycle.

Planning■ Acquire a prism to use in the

Quick Demo.■ Acquire colored lights for the

plant growth project.■ Purchase Elodea for the

BioLab.■ Collect objects to model pho-

tosynthesis for MiniLab 9-1.■ Obtain leaves and acetone for

the leaf pigment project.


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How does the amount of gas in each test tube differ?

Oxygen is a product of a process called photosynthesis, whichoccurs in plants. Based on the results shown, what is requiredfor photosynthesis to occur?

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Gifted Linguistic The citric acid cycle issometimes called the Krebs cycle.

Have students research the work of MelvinCalvin or Hans Krebs and write a report.

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Resource ManagerResource ManagerSection Focus Transparency 22 and

MasterConcept Mapping, p. 9Basic Concepts Transparency 12 and

Master

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Electroncarrier

proteins

Light

Chlorophyll

Chlorophyll

NADP+

+H+

ADP+

ATPNADPH

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Electron Transport Chains

hydrogen ions into the center of thethylakoid disc.

After the electron has traveleddown the first electron transportchain, it is passed down a secondelectron transport chain. Followingthe second electron transport chain,the electron is still very energized. Sothat this energy is not wasted, theelectron is transferred to the stromaof the chloroplast. To do this, anelectron carrier molecule calledNADP+ (nicotinamide adenine dinu-cleotide phosphate) is used. Whencarrying the excited electron, NADP+

combines with a hydrogen ion andbecomes NADPH.

Just as proteins contain a bindingsite where they can bind ATP, so theNADP+ molecule and other electroncarrier molecules like it have a bind-ing site for energized electrons.However, in this case, NADPH doesnot use the energy present in theenergized electron; it simply storesthe energy until it can transfer it toanother series of reactions that willtake place in the stroma. There,NADPH will play an important rolein the formation of carbohydrates.The light-dependent reactions aresummarized in Figure 9.6.


Figure 9.6The Light Reactions

Light-Dependent Reactions

Light energy

Chlorophyllpasses energy

down through theelectron transport chain,

providing energy that

transfers to chlorophyll

Sun

splitsH2O

bonds to ADP

formingATPH+

oxygenreleased

for use in thelight-independent reactions

NADP+

NADPH

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View an animation of the light-dependent reactions in the PresentationBuilder of the InteractiveCD-ROM.

CD-ROM

This expanded viewshows energized elec-trons lose some energyas they are passed fromprotein to proteinthrough the electrontransport chain. Thisenergy can be used toform ATP or NADPH.

BB

Chlorophyll molecules absorb light energy and energizeelectrons for producing ATP or NADPH.

AA

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Skill Have students writethe equation that summarizesphotosynthesis. Ask them to iden-tify the raw materials (reactants)in the process and the products.Carbon dioxide and water are theraw materials; simple sugars andoxygen are the products. Guide stu-dents to an understanding of whatthe equation means in terms ofenergy capture and conversion.L2

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How does photosyn-thesis vary with lightintensity? Photo-synthesis is the processby which green plantssynthesize organiccompounds from waterand carbon dioxideusing energy absorbedby chlorophyll fromsunlight.

AnalysisGreen plants were exposed to increasing light intensity,

as measured in candelas, and the rate of photosynthesis wasmeasured. The temperature of the plants was kept constantduring the experiment. The graph shown here depicts thedata obtained.

Thinking CriticallyConsidering the overall equation for photosynthesis,

make a statement summarizing what the graph shows. Undernormal field conditions, what factors may limit the relativerate of photosynthesis when the light intensity is increasedand temperature remains constant?

Problem-Solving Lab 9-2Problem-Solving Lab 9-2 Drawing ConclusionsTo trap the energy in the sun’s

light, the thylakoid membranes con-tain pigments, molecules that absorbspecific wavelengths of sunlight. Themost common pigment in chloro-plasts is chlorophyll. Chlorophyll informs a and b absorbs most wave-lengths of light except for green.Because chloroplasts have no meansto absorb this wavelength, it isreflected, giving leaves a greenappearance. In the fall, trees reabsorbchlorophyll from the leaves and otherpigments are visible, giving leaves likethose in Figure 9.5 a wide variety ofcolors. Read the Chemistry Connectionat the end of this chapter to find outmore about biological pigments.

Light-DependentReactions

The first phase of photosynthesisrequires sunlight. As sunlight strikesthe chlorophyll molecules in the thy-lakoid membrane, the energy in thelight is transferred to electrons.These highly energized, or excited,electrons are passed from chlorophyllto an electron transport chain, aseries of proteins embedded in thethylakoid membrane. Use theProblem-Solving Lab shown here toconsider how light intensity affectsphotosynthesis.

Each protein in the chain passesenergized electrons along from pro-tein to protein, similar to a bucketbrigade in which a line of people passa bucket of water from person to per-son to fight a fire. At each step alongthe transport chain, the electron losesenergy, just as some of the watermight be spilled from buckets in thefire-fighting chain. The electrontransport chain allows small amountsof the electron’s energy to be releasedat a time. This energy can be used toform ATP from ADP, or to pump


Figure 9.5The red, yellow, andpurple pigments arevisible in the autumnwhen trees reabsorbchlorophyll.

Rate

of p

hoto

synt

hesis

500 1000 1500 2000Light intensity (candelas)

80

40

20

60

0

Light Intensity and Photosynthesis

OriginWORDWORD

chlorophyllFrom the Greekwords chloros, mean-ing “pale yellowish-green,” and phyllon,meaning “leaf.”Chlorophyll is agreen pigmentfound in leaves.

232

2 Teach

Purpose Students will examine the effectof increasing light intensity onthe rate of photosynthesis.

Process Skillsrecognize cause and effect, inter-pret data, analyze data

BackgroundPlants depend on the energyderived from light to synthesizeorganic compounds from carbondioxide and water.

Teaching Strategies■ Ask students how horticultur-ists increase light intensity, espe-cially during winter. They usegrow lights and sun reflectors.■ Ask students why keepingtemperature constant during theexperiment is important. Thisavoids introducing another variable.

Thinking CriticallyThe rate of photosynthesisincreases with increasing lightintensity until another factor lim-its the rate. Limiting factorsinclude the availability of water,carbon dioxide, phosphate, ADP,and enzymes.

Performance Have stu-dents work in groups to designand carry out an experiment thatuses grow lights to test whetherincreasing light intensity increasesthe rate of photosynthesis. Usethe Performance Task AssessmentList for Designing an Experimentin PASC, p. 23.

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PortfolioPortfolio

Communicating about ScienceInterpersonal Divide the class intothree groups. Ask each group to dis-

cuss chloroplasts, the light reactions, or the Calvin cycle and present a short report.Individual students should place copies oftheir group report in their portfolios.

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Use a prism to show how visiblelight can be separated into aspectrum. Students may recallfrom their study of physical sci-ence that the different colorsof the visible spectrum repre-sent different wavelengths oflight.

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P R O J E C TGrowing Plants in Colored Light

Kinesthetic Have students place aplant in each of several closed boxes

containing a colored light bulb. Using cau-tion, tape the opening through which theelectric cord passes so no outside light canenter. Provide the plants in each box with

equal amounts of water. Have studentshypothesize how the plants in each box willgrow compared with a control plant.

Ask students to write a summary of theexperiment. Students should include resultsand observations and an evaluation of thehypothesis.

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The BioLab at theend of the chaptercan be used at thispoint in the lesson.

INTERNETINTERNET

CD-ROMBiology: The Dynamicsof Life

Animation: The Light ReactionsDisc 1

VIDEODISCBiology: The Dynamicsof Life

Light Reactions (Ch. 26)Disc 1, Side 1, 51 sec.

!9hÜ"

VIDEODISCThe Secret of Life Chloroplast Membrane Structure

!7;;tG"

C C C C C

C

C C C C C C

C C C

C C C

C C CC C C

C C CC C C

C C C C C C

C C C

(Glucose)

(PGA)ADP +

ADP + ATP

ATP

NADP+

NADPH

(RuBP)

(CO2)

(Unstable intermediate)

(PGAL)(PGAL)

(PGAL)

CalvinCycle

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Magnification: 13 450�

The stroma in chloroplastshost the Calvin cycle

INSIDESSTORTORYY

INSIDE

The Calvin Cycle

The Calvin cycle takes the carbon in CO2 and forms carbohydrates through a series of reactions in the

stroma of the chloroplast. NADPH and the ATP produced during the earlier light-dependent reactions are importantmolecules for this series of reactions.

Critical Thinking Environmentalists are concerned about the increasing loss of Earth’s forests. How is the Calvin cycleconnected to this concern?

PGA formation The six-carbonsugar formed in Step 1 is then splitto form two molecules of phos-phoglyceric acid (PGA).

22

Use of ATP and NADPHA series of reactions involv-ing ATP and NADPH fromthe light-dependent reac-tions, converts a moleculeof PGA into phosphoglycer-aldehyde (PGAL), anotherthree-carbon molecule.

33

Glucose productionAfter several rounds of theCalvin cycle, two moleculesof PGAL leave the cycle toform glucose.

44

ATP and PGALreplenish RuBPSome PGAL moleculesreform the five-car-bon sugar with thehelp of energy fromATP. Each five-carbonRuBP is ready tobegin the cycle again.

55

Carbon fixation One carbonatom from CO2 is added to afive-carbon sugar called ribu-lose biphosphate (RuBP).

11

IINSIDENSIDESSTORTORYY

INSIDE

Purpose Students will learn the steps ofthe Calvin cycle and how CO2 isused to make glucose.

BackgroundEnergy from the light reactions isused to make sugar moleculesthat will serve as a long-termstorage for energy.

Teaching Strategies■ Have students identify themain steps of the Calvin cycle.

Visual Learning■ Have students make a chart of

everything required for oneround of the Calvin cycle,including the number of mole-cules.

Critical ThinkingThe Calvin cycle is critical tophotosynthesis and carbohydrateproduction. If less photosynthesisoccurs, fewer food molecules areproduced.

3 AssessCheck for UnderstandingStudents should know the gen-eral equation for photosynthesisand understand that the lightreactions feed the Calvin cycle.

ReteachExplain that the Calvin cycle usesCO2 and hydrogen to form thesimple sugars that make morecomplex carbohydrates.

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Sun

O2 + 4H+

2H2O

4e–

2H2O 4H+ + O2 + 4e–

Use Isotopes to UnderstandPhotosynthesis C. B. van Niel discov-ered the steps of photosynthesis whenhe used radioactive isotopes of oxygenas tracers. Radioactive isotopes areused to follow a particular moleculethrough a chemical reaction.

Procedure! Study the following equation for photosynthesis

that resulted from the van Niel experiment:6CO2 + 6H2O* ➜ C6H12O6 + 6O2*

@ Radioactive water, water tagged with an isotope of oxy-gen as a tracer (shown with the *), was used. Note wherethe tagged oxygen in water ends up on the right side ofthe chemical reaction.

# Assume that van Niel repeated his experiment, but thistime he put a radioactive tag on the oxygen in CO2.

$ Using materials provided by your teacher, model what youwould predict the appearance of his results would be.Your model must include a “tag” to indicate the oxygenisotope on the left side of the arrow as well as where itends up on the right side of the arrow.

% You must use labels or different colors in your model toindicate also the fate of carbon and hydrogen.

Analysis1. Explain how an isotope can be used as a tag.2. Using your model, predict:

a. the fate of all oxygen molecules that originated fromcarbon dioxide.

b. the fate of all carbon molecules that originated fromcarbon dioxide.

c. the fate of all hydrogen molecules that originatedfrom water.

MiniLab 9-1MiniLab 9-1Restoring electrons to chlorophyll

Although some of the light-ener-gized electrons may be returned tochlorophyll after they’ve movedthrough the electron transport chain,many leave with NADPH for thelight-independent reactions. If theseelectrons are not replaced, the chloro-phyll will be unable to absorb lightand the light-dependent reactions willstop, as will the production of ATP.

To replace the lost electrons, mol-ecules of water are split. Each watermolecule produces one-half moleculeof oxygen gas, two hydrogen ions,and two electrons. This reaction isshown in Figure 9.7 and is calledphotolysis (FO tohl ih sis). The oxy-gen of photolysis supplies the oxygenwe breath. The MiniLab on this pagedescribes how scientists traced oxygenthrough photosynthesis.

Light-IndependentReactions

The second phase of photosynthe-sis does not require light. It is calledthe Calvin cycle, which is a series ofreactions that use carbon dioxide toform carbohydrates. The Calvin cycletakes place in the stroma of thechloroplast. What are the stages of theCalvin cycle? To find out, read theInside Story.


Figure 9.7In photolysis, two mole-cules of water are splitto replace electrons lostfrom chlorophyll.

van Niel

OriginWORDWORD

photolysisFrom the Greekwords photos, mean-ing “light,” andlyein, meaning “tosplit.” Light energysplits water mole-cules in photolysis.

Formulating Models

234

Purpose Students will build a model totrace the fate of molecules in-volved in photosynthesis.

Process Skillsanalyze information, define oper-ationally, formulate models, thinkcritically, predict

Teaching Strategies■ Models may be constructedfrom colored beads, Legos,Tinkertoys, or colored clay. Makesure that students provide a key(probably by color) to show themolecules being referenced.

■ If materials for modeling arenot available, students can tracemolecules from the left to rightside of the equation by usinglines and arrows.

Expected ResultsStudent models will show that allcarbon from carbon dioxide endsup in glucose (CH2O); all oxygenfrom carbon dioxide ends up inglucose and water; all hydrogenfrom water (on the left side) endsup in glucose and water.

Analysis1. Student answers may vary.

Isotopes are radioactive andthus can be traced by theirradioactivity.

2. a. incorporated into glucoseor waterb. incorporated into glucosec. incorporated into glucoseand water

Knowledge Have studentsmodel the equation for photosyn-thesis starting with an isotope ofhydrogen in the water molecule tothe left of the arrow. Use thePerformance Task Assessment Listfor Model in PASC, p. 51. L2

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MiniLab 9-1MiniLab 9-1


Oxygen JourneyLinguistic After the class has per-formed MiniLab 9-1, have the stu-

dents write a story describing the pathwaytaken by the radioactively labeled oxygenin the van Niel experiment. Encourage cre-ativity while at the same time conveyingbiological accuracy.

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P R O J E C TExtracting and Testing PigmentsHave students soak ground, fresh leaves inwarm alcohol and apply the extract to a 12-cm-long strip of filter paper in a narrowband about 2 cm from the bottom of thestrip. Place the filter paper into a test tubecontaining a small amount of acetone (clearfingernail polish remover). Tightly seal the

test tube. Just the bottom edge of the papershould dip into the solvent; the leaf extractshould not be immersed.

As the solvent is drawn up the paper, lesssoluble compounds remain near the bottomand more soluble compounds are carriedhigher. Remove the paper strip before thesolvent reaches the top. L3

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VIDEODISCThe Secret of LifeThe Calvin Cycle

!7;\LI"

Resource ManagerResource ManagerReinforcement and Study Guide

pp. 38-39BioLab and MiniLab Worksheets, p. 39

Critical Thinking/Problem Solving, p. 9L3

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235

the products can be used again to initiate the cycle.

In the electron transport chain,you learned that an energized elec-tron is passed from protein to proteinand the energy is slowly released. Youcan imagine that making a complexcarbohydrate from a molecule ofCO2 would be a large task for a cell,so the light-independent reactions inthe stroma of the chloroplast breakdown the complicated process intosmall steps. Each sugar moleculemade by the Calvin cycle contains sixcarbon atoms, and because only onemolecule of CO2 is added to the cycleeach time, it takes a total of sixrounds of the cycle to form one sugar.

CAREERS IN BIOLOGY

Biochemist

If you are curious about what makesplants and animals grow and

develop, consider a career as a bio-chemist. The basic research of bio-chemists is to understand howprocesses in an organism work toensure the organism’s survival.

Skills for the JobA bachelor’s degree in chemistry or biochemistry will

qualify you to be a lab assistant. For a more involved position,you will need a master’s degree; advanced research requires aPh.D. Some biochemists work with genes to create new plantsand new chemicals from plants. Others research the causesand cures of diseases or the effects of poor nutrition. Still oth-ers investigate solutions for urgent problems, such as findingbetter ways of growing, storing, and caring for crops.

To find out more about careers in biologyand related fields, visit the Glencoe Science

Web Site. www.glencoe.com/sec/science

The Calvin cycleThe Calvin cycle, named after

Melvin Calvin shown in Figure 9.8,is called a cycle because one of thelast molecules formed in the series ofchemical reactions is also one of themolecules needed for the first reac-tion of the cycle. Therefore, one of



Understanding Main Ideas1. Why do you see green when you look at a leaf

on a tree? Why do you see other colors in thefall?

2. How do the light-dependent reactions of photosynthesis relate to the Calvin cycle?

3. What is the function of water in photosynthesis?Explain the reaction that achieves this function.

4. How does the electron transport chain transferlight energy in photosynthesis?

Thinking Critically5. In photosynthesis, is chlorophyll considered a

reactant, a product, or neither? How does therole of chlorophyll compare with those of CO2and H2O?

6. Designing an Experiment Design an experi-ment that would simulate photosynthesis. Formore help, refer to Practicing Scientific Methodsin the Skill Handbook.


Figure 9.8Melvin Calvin

236

ExtensionIntrapersonal Have studentsresearch the difference be-

tween the chlorophyll of plantsand the light-capturing pigmentsof photosynthetic bacteria.

Performance Ask studentsto write a paragraph summarizingthe citric acid cycle. L2

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LSCareer Path Courses in high school:chemistry, mathematics,

biology, other scienceCollege: bachelor’s and master’sdegree in biochemistry, chem-istry; doctorate required foradvanced research or manage-ment

Career IssueDebate whether biochemistsshould clone animals.

For More InformationWrite to the

American Society for Biochemistry and Molecular Biology

9650 Rockville PikeBethesda, MD 20814.

4 CloseDiscussionAsk students where the energy intheir food comes from. Studentsshould trace energy to the sun.Work through some simple foodchains as part of the discussion.L1

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Section AssessmentSection AssessmentSection Assessment1. The chlorophyll in the leaf reflects green

and yellow while absorbing other colors.In the fall, chlorophyll is absorbed,revealing other leaf pigments.

2. ATP and hydrogen ions from the lightreactions are used in the Calvin cycle.

3. Photolysis splits water to provide hydro-gen ions for the Calvin cycle and restoreelectrons to chlorophyll.

4. Proteins convey energized electronsthrough the chloroplast.

5. Chlorophyll is neither a reactant nor aproduct. It contributes electrons to pho-tosynthesis but is not changed during thereaction. CO2 and H2O are reactants.

6. Students could demonstrate how solarpanels convert sunlight to electricity.

CAREERS IN BIOLOGY

Section

Cellular RespirationThe process by which mitochon-

dria break down food molecules toproduce ATP is called cellular respiration. There are three stages ofcellular respiration: glycolysis, the cit-ric acid cycle, and the electron trans-port chain. The first stage, glycolysis,is anaerobic—no oxygen is required.The last two stages are aerobic andrequire oxygen to be completed.

GlycolysisGlycolysis (gli KOL ih sis) is a

series of chemical reactions in the

cytoplasm of a cell that break downglucose, a six-carbon compound, intotwo molecules of pyruvic (pie RUEvik) acid, a three-carbon compound.Because two molecules of ATP areused to start glycolysis, and only fourATP molecules are produced, glycol-ysis is not very efficient, giving a netprofit of only two ATP molecules foreach glucose molecule broken down.

In the electron transport chain ofphotosynthesis, an electron carriercalled NADP+ was described as car-rying energized electrons to anotherlocation in the cell for further chemi-cal reactions. Glycolysis also uses an

9.3 GETTING ENERGY TO MAKE ATP 237

You know that the chlorophyll ingreen plants is the key to photo-synthesis. You also know that

your body needs energy to survive.What would it be like if you hadchlorophyll in your skin and could con-vert light energy to carbohydrates toproduce ATP? People would look quitedifferent. Fortunately, the mitochon-dria in your cells can convert the carbo-hydrates that green plants formed bythe Calvin cycle into ATP. This allowsyou to access the sun’s energy through the work done by plant cells.

SECTION PREVIEW

ObjectivesCompare and contrastcellular respiration andfermentation.Explain how cellsobtain energy from cellular respiration.

Vocabularycellular respirationanaerobicaerobicglycolysiscitric acid cyclelactic acid fermentationalcoholic fermentation

9.3 Getting Energy to Make ATP

OriginWORDWORD

anaerobicFrom the Greekwords an, meaning“without,” andaeros, meaning “air.”Anaerobic organ-isms can live with-out oxygen.

Magnification:221 875�

Human cells produceenergy in mitochondria(inset).

237

Section 9.3

PrepareKey ConceptsStudents will learn the similari-ties and differences between cel-lular respiration and anaerobicprocesses that release energy.They will also learn how thesereactions are related to photosyn-thesis.

Planning■ Purchase baker’s yeast for the

Quick Demo and MiniLab 9-2.

■ Obtain Coleus plants andiodine solution and othermaterials for the AlternativeLab.


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Which of these organisms require energy?

How does the manner in which these organisms get energy differ?

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Transparency Cellular Respiration23 SECTION FOCUS

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Cultural Diversity

Severo OchoaHave students research the efforts ofSpanish-American biochemist Severo Ochoa(1905–1993) toward the modern understand-ing of the citric acid cycle and photosynthe-sis. Ochoa showed how the oxidation of oneglucose molecule could yield 38 ATP mole-cules. He also elucidated the mechanisms of

the citric acid cycle and photosynthesis byidentifying the function of key enzymes.

Ochoa’s research in cellular respiration inthe 1930s and 1940s resulted ultimately inthe discovery of the mechanisms of RNA andDNA synthesis, for which Ochoa and col-league Arthur Kornberg received a Nobelprize in 1959. L3

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Recycling of oxaloacetic acidSuccinic acid under-goes a series of reactions inwhich FADH and NADH areformed and oxaloacetic acid is again made available for the cycle.

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NAD+

NAD+

NAD+

C C

NADH + H+

ATP

FADH

NADH + H+

ADP +

Acetyl CoA

Malic acid

Fumaric acid

Oxaloacetic acid

Succinic acid

Citric acid

Ketoglutaric acid

CitricAcidCycle

O O

O O

NADH + H+

C C C C

C C C C

C C C C

C C C C

C C C C C C

C C C C C

C

C



The mitochondria host the citric acid cycle.

INSIDESSTORTORYY

INSIDE

Citric acid The two-carbon com-pound acetyl-CoA reacts with afour-carbon compound calledoxaloacetic acid to form citric acid, a six-carbon molecule.

11

Formation of the second CO2 Another moleculeof CO2 is released, forming a four-carbon compound,succinic acid. One molecule of ATP and a molecule of NADH are also produced.

33

The Citric Acid Cycle

The citric acid cycle takes a molecule of acetyl-CoA and breaks it down, forming ATP and CO2.

The electron carriers NAD+ and FAD pick up energizedelectrons and pass them to the electron transport chainin the inner mitochondrial membrane.

Critical Thinking How many ATP molecules are pro-duced by a single turn of the citric acid cycle?

Formation of CO2 A moleculeof CO2 is formed, reducing theeventual product to a five-carboncompound, ketoglutaric acid.

In the process, a molecule ofNADH is produced.

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239

IINSIDENSIDESSTORTORYY

INSIDE

Purpose To teach students the main eventsof the citric acid cycle that breakdown acetyl CoA to form ATP,NADH, FADH2, and carbondioxide.

BackgroundGlycolysis initiates the break-down of glucose. Pyruvate, theend product of glycolysis, under-goes a series of reactions to formacetyl CoA, which enters the cit-ric acid cycle. The citric acidcycle is important for its largeenergy yield.

Teaching Strategies■ Ask students to describe thefour stages of the citric acid cycle.Include the products for eachstage.

Visual LearningMake a table with the followingheadings: ATP, NADH, andFADH2. Under the headings listone round of the citric acid cycle.Have the students fill in the num-ber of each molecule producedduring one round.

Critical ThinkingEach round produces:1 ATP = 1 ATP3 NADH � 3 ATP/NADH =

9 ATP1 FADH2 � 2 ATP/FADH2 =

2 ATPTOTAL = 12 ATP

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electron carrier called NAD+ (nicotin-amide adenine dinucleotide). NADforms NADH when it is carrying anelectron. Glycolysis is an anaerobicprocess as you can see by the absenceof oxygen in the equation shown inFigure 9.9.

Following glycolysis, the pyruvicacid molecules move to the mito-chondria, the organelles that produceATP for the cell. In the presence ofoxygen, two more stages completecellular respiration: the citric acidcycle (also known as the Krebs cycle)and the electron transport chain ofthe mitochondrion. Before these twostages can begin, however, pyruvicacid undergoes a series of reactions inwhich it loses a molecule of CO2 andcombines with coenzyme A to formacetyl-CoA. The reaction with coen-zyme A produces a molecule ofNADH and H+. These reactions areshown in Figure 9.10.

The citric acid cycleThe citric acid cycle is a series of

chemical reactions similar to theCalvin cycle in that one of the mole-cules needed for the first reaction isalso one of the end products.However, in the Calvin cycle, glucosemolecules are formed; in the citricacid cycle, glucose is broken down.What is the first compound thatacetyl-CoA combines with in the cit-ric acid cycle? To learn the answer,look at the Inside Story.

In the process of breaking downglucose, one molecule of ATP is pro-duced for every turn of the cycle. Twoelectron carriers are used, NAD+ andFAD (flavin adenine dinucleotide). Atotal of three NADH + H+ moleculesand one FADH2 molecule areformed. These electron carriers passthe energized electrons along to theelectron transport chain in the innermembrane of the mitochondrion.


C C C CC C C P

C C C

C C C

C C CPC C

ENERGY ENERGY

2ATP2ADP

4ADP + 4 P

2NAD+2PGAL

Glucose

4ATP

2NADH + 2H+

2 Pyruvicacid

Figure 9.9Glycolysis breaksdown a molecule ofglucose into twomolecules of pyruvicacid. In the process, itforms a net profit oftwo molecules ofATP, two moleculesof NADH , and twohydrogen ions.

C C C C C C C C C CC

NAD+

CO2

NADH + H+

Pyruvicacid

Outside themitochondrion

Mitochondrialmembrane

Coenzyme A

Pyruvicacid

Inside themitochondrion

Intermediateby-product

- CoAAcetyl-CoA

+

Figure 9.10As a result of thereactions that con-vert pyruvic acid toacetyl-CoA within themitochondrion, amolecule of NADHand H+ are formed.

Glycolysis

238

2 TeachConcept DevelopmentRead a recipe for making bread.Explain to students that the yeastused in the recipe are microor-ganisms classified as fungi.Discuss how, unlike most organ-isms, yeast carry out processesthat release energy in the absenceof oxygen. Explain that bakersuse yeast in their recipes foralmost all breads, because as yeastfunction anaerobically, theyrelease CO2, which causes thebread to rise.

ReinforcementMake sure students understandthat pyruvic acid is the intermedi-ate product for both types of fer-mentation. Challenge students toexplain how pyruvic acid changesin each type of fermentation.

Concept DevelopmentFor students having difficultywith the concepts of this chapter,review the roles of a producerand consumer. Relate theprocesses in this chapter to theconcepts of Unit 2, Ecology.


Prepare a sugar solution bymixing a tablespoon of sugarwith a cup of warm water in adeep jar or flask. Add somebaker’s yeast a few hoursbefore class. Have studentsnote the odor of alcohol andthe bubbles of carbon dioxide.Point out that these productsresult as the yeast carry outalcoholic fermentation.

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Cycle ComparisonVisual-Spatial Have students makea poster of the citric acid cycle.

Compare it to the Calvin cycle. Note thatthe Calvin cycle uses ATP and electron car-riers such as NADP to produce glucosewhile the citric acid cycle produces ATPand electron carriers, including NADH andFADH2, as it burns glucose. L2

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!:_MHkBD"Breakdown of Pyruvic

Acid!7;YLF"Glycolysis

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Section Focus Transparency 23and Master

Basic Concepts Transparency13 and Master

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Fermentation

There are times when your cellsare without oxygen for a short periodof time. When this happens, ananaerobic process called fermenta-tion follows glycolysis and provides ameans to continue producing ATPuntil oxygen is available again. Someorganisms exist in anaerobic environ-ments and use fermentation to pro-duce energy. There are two majortypes of fermentation: lactic acid fer-mentation and alcoholic fermenta-tion. Figure 9.12 and Table 9.1 com-pare the two processes. Perform theProblem-Solving Lab shown here tofurther compare and contrast cellularrespiration and fermentation.


Is cellular respiration better than fermentation? Themethods by which organisms derive ATP from their food maydiffer; however, the result, the production of ATP molecules,is similar.

AnalysisStudy Table 9.1 and evaluate cellular respiration, lactic

acid fermentation, and alcoholic fermentation.

Thinking Critically1. Describe some of the reasons why cellular respiration pro-

duces so much more ATP than does fermentation.2. Describe a situation when a human would use more than

one of the above processes.3. Think of an organism that might generate ATP only by

fermentation and consider why fermentation is the bestprocess for the organism.

Problem-Solving Lab 9-3Problem-Solving Lab 9-3 AcquiringInformation

Figure 9.12Fermentation produces ATP when oxygenfor respiration is scarce.

Lactic acid

glucose

glycolysis (pyruvic acid)

lactic acid+

2 ATP

Alcoholic

glucose


carbon dioxide+

alcohol+

2 ATP

Cellular respiration

glucose


carbon dioxide+

water+

38 ATP

Table 9.1 Comparison of lactic acid and alcoholic fermentation

Lactic acid and alcoholic fermentation are compa-rable in the production of ATP, but compared tocellular respiration, it is obvious that fermenta-tion is far less efficient in ATP production.

AA

Lactic acid fermenta-tion occurs in somebacteria, in plants,and in most animals,including humans.

BB

Purpose Students will compare and con-trast the process of aerobic respi-ration, lactic acid fermentation,and alcoholic fermentation.

Process Skillsthink critically, compare and con-trast, acquire information, ana-lyze information, sequence,define operationally

Teaching Strategies■ It will be necessary for stu-dents to review the sections deal-ing with aerobic respiration,lactic acid fermentation, andalcoholic fermentation beforethey attempt to complete this lab.

Thinking Critically

1. The chemical reactions of thecitric acid cycle provide moreATP than does fermentation.Cellular respiration bettermeets the energy require-ments of complex organisms.

2. Humans normally carry outcellular respiration. During atime of intense exercise, werevert to lactic acid fermenta-tion.

3. For an organism that lives inanaerobic conditions and usessmall amounts of energy, cel-lular respiration may not beeconomical if fermentationconsistently provides suffi-cient energy.

Skill Provide an incom-plete table similar to Table 9.1and have the students complete it.Use the Performance TaskAssessment List for Data Table inPASC, p. 37. L1

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and let it absorb the iodine for a fewminutes. CAUTION: Iodine is an irritant.Rinse thoroughly if iodine gets on skin orclothing.

7. Rinse the leaf with tap water andobserve.

Analysis1. What happens when the leaf is boiled in

alcohol? Its chlorophyll dissolves.2. In what part of the leaf did carbon fixa-

tion slow or stop? The covered part

received no light and therefore could notcarry on photosynthesis, which is a car-bon fixation process.

Performance Have students writea summary of the lab. Use the Perform-ance Task Assessment List for Lab Reportin PASC, p. 47. L2

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H+ H+

H+

H+

H+

H+

P

Electroncarrier proteins

Electronpathway

Intermembranespace

ATPsynthase

ADP + ATP

Innermembrane

Matrix

NAD+

FAD

NADH

FADH2

4 H+ + O2 H2O

H2O

The electron transport chainThe electron transport chain in

the inner membrane of the mito-chondrion is very similar to the elec-tron transport chain of the thylakoidmembrane in the chloroplast of plantcells during photosynthesis. NADHand FADH2 pass energized electronsfrom protein to protein within themembrane, slowly releasing smallamounts of the energy containedwithin the electron. Some of thatenergy is used directly to form ATP;some is used to pump H+ ions intothe center of the mitochondrion.Consequently, the mitochondrioninner membrane becomes positivelycharged because of the high concen-tration of positively charged hydro-gen ions. At the same time, the exte-rior of the membrane is negativelycharged, which further attractshydrogen ions. The gradient thatresults is both electrical and chemi-cal: electrical because of the chargedifference; chemical because of theconcentration difference.

The inner membrane of the mito-chondrion forms ATP from this elec-

trochemical gradient of H+ ionsacross the membrane, just as the thy-lakoid membranes did in the chloro-plasts. The electron transport chainand the formation of ATP are shownin Figure 9.11.

The final electron acceptor in thechain is oxygen, which reacts withfour hydrogen ions (4H+) to form twomolecules of water (H2O). This is whyoxygen is so important to our bodies.Without oxygen, the proteins in theelectron transport chain cannot passalong the electrons. If a protein can’tpass an electron along, it cannotaccept another electron either. Veryquickly, the entire chain becomesblocked and the aerobic processes ofcellular respiration cannot occur.

Overall, the electron transportchain produces 32 ATP molecules.Obviously, the aerobic method ofATP production is very effective.However, an anaerobic process canproduce ATP for short periods oftime in the absence of oxygen, but itis not efficient enough to generatesufficient quantities of ATP for all ofthe cell’s needs.


Figure 9.11In the electron trans-port chain, the carriermolecules NADH and FADH2 give upelectrons that passthrough a series ofreactions. Oxygen is the final electronacceptor.

Skill Make a table summa-rizing the production and usageof ATP molecules in variousstages of respiration. L2

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Alternative LabCarbon Fixation

Purpose Students will demonstrate that withoutlight carbon fixation slows or stops.Materialsblack paper, labels, iodine solution, Coleusplants, paper clip, hot plate, beaker, 95%

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alcohol, small bowlProcedure

1. Cut out two identical pieces of blackpaper in the shape of a small square.

2. Stick a label on one piece and writeyour initials and the date on it.

3. Use a paper clip to fasten the blackshapes to the top and bottom surfacesof a Coleus leaf so that they arematched up exactly.

4. Leave the plant in sunlight for 7 days.

Then remove the leaf that was partiallycovered and take off the paper clipand papers.

5. Place the leaf into a beaker of boiling95% alcohol enclosed in a fume hoodand boil it until it turns white. CAU-TION: Do not use a heat source thathas an open flame or a hot plate withan unsealed element.

6. Remove the leaf and place it in a smallbowl. Pour iodine solution on the leaf240

Deforestation Many forests, especially tropi-cal rain forests, are being lev-eled to provide fuel anduncover farmland. Scientistsare considering how the mas-sive clearance of forestedlands will affect the balancebetween photosynthesis andrespiration in the biosphere.Have students use the Internetto investigate scientific mod-els of deforestation anddevelop a plan to ease theimbalance. L2

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VIDEODISCThe Secret of LifeElectron Transport Chain

!7;Z~B"


Reteaching Skills Trans-parencies 14 and 15 andMasters

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ComparingPhotosynthesis andCellular Respiration

The production and breakdown offood molecules are accomplished bydistinct processes that bear certainsimilarities. Both photosynthesis andcellular respiration use electron carri-ers and a cycle of chemical reactionsto form ATP. Both use an electrontransport chain to form ATP and tocreate a chemical and a concentrationgradient of H+ within a cell. Thishydrogen gradient can be used toform ATP by an alternative process.

However, despite using such simi-lar tools, the two cellular processesaccomplish quite different tasks.Photosynthesis produces high-energycarbohydrates and oxygen from thesun’s energy, whereas cellular respira-tion uses oxygen to break down carbo-hydrates to form ATP and compoundswith a much lower level of energy.Also, one of the end products of cellu-lar respiration is CO2, which is one ofthe beginning products for photosyn-thesis. The oxygen produced duringphotosynthesis is a critical moleculenecessary for cellular respiration.Table 9.2 in Figure 9.14 comparesthese complementary processes.



Understanding Main Ideas1. Compare the ATP yields of glycolysis and aerobic

respiration.2. How do alcoholic and lactic acid fermentation differ?3. How is most of the ATP from aerobic respiration

produced?4. When is lactic acid fermentation important to the

cell?

Thinking Critically5. Compare the energy-producing processes in a

jogger’s leg muscles with those of a sprinter’s

leg muscles. Which is likely to build up more lactic acid? Which runner is more likely to be outof breath after running? Explain.

6. Making and Using Tables Use the sectioncalled Comparing Photosynthesis and CellularRespiration to make a set diagram summarizingthe similarities and differences between the two processes. For more help, refer toOrganizing Information in the Skill Handbook.


Photosynthesis

food accumulated

energy from sun stored in glucose

carbon dioxide taken in

oxygen given off

produces glucose from PGAL

goes on only in light

occurs only in presence of chlorophyll

Cellular Respiration

food broken down

energy of glucose released

carbon dioxide given off

oxygen taken in

produces CO2 and H2O

goes on day and night

occurs in all living cells

Table 9.2 Comparison of photosynthesis and cellular respirationFigure 9.14Photosynthesis andcellular respirationare complementaryprocesses. Therequirements of oneprocess are the prod-ucts of the other.

3 AssessCheck for Understanding

Visual-Spatial Provide stu-dents with a list of the major

substances discussed and thenames of the associated processes(glycolysis, respiration, alcoholicfermentation, lactic acid fermen-tation, and electron transportchain). Have students construct atable that identifies whether eachsubstance is a product or reactantof each process.

ReteachProvide students with unlabeleddiagrams of glycolysis, alcoholicfermentation, and lactic acidpathways. Have them fill in thelabels as you discuss theprocesses.

ExtensionHave students find out andreport on how cyanide affectsrespiration.

Portfolio Ask students towrite summaries of glycolysis, cit-ric acid cycle, electron transportchain, and fermentation.

4 CloseDiscussionDiscuss the importance oflactic acid fermentation in

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Determine if Apple JuiceFerments Organisms such asyeast have the ability to breakdown food molecules and syn-thesize ATP when no oxygen isavailable. When the appropri-ate food is available, yeast cancarry out alcoholic fermenta-tion, producing CO2. Thus, theproduction of CO2 can be usedto judge whether alcoholic fer-mentation is taking place.

Procedure! Carefully study the diagram

and set up the experimentas shown.

@ Hold the test tube in abeaker of warm (not hot)water and observe.

Analysis1. What were the gas bubbles that came from the plastic

pipette?2. Predict what would happen to the rate of bubbles given

off if more yeast were present in the mixture.3. Why was the test tube placed in warm water?4. On the basis of your observations, was this process aerobic

or anaerobic?

MiniLab 9-2MiniLab 9-2 PredictingLactic acid fermentation

Lactic acid fermentation is one ofthe processes that supplies energywhen oxygen is scarce. You know thatunder anaerobic conditions, the elec-tron transport chain backs up becauseoxygen is not present as the final electron acceptor. As NADH andFADH2 arrive with energized elec-trons from the citric acid cycle andglycolysis, they cannot release theirenergized electrons to the electrontransport chain. The citric acid cycleand glycolysis cannot continue with-out a steady supply of NAD+ andFAD.

The cell does not have a methodto replace FAD during anaerobicconditions; however, NAD+ can bereplaced through lactic acid fermen-tation. In lactic acid fermentation,two molecules of pyruvic acid useNADH to form two molecules oflactic acid. This releases NAD+ to beused in glycolysis, allowing two ATPmolecules to be formed for each glu-cose molecule. The lactic acid istransferred from muscle cells, whereit is produced during strenuous exer-cise, to the liver that converts it backto pyruvic acid. The lactic acid thatbuilds up in muscle cells results inmuscle fatigue.

Alcoholic fermentation

Another type of fermentation,alcoholic fermentation, is used by, among others, yeast cells to pro-duce CO2 and ethyl alcohol. Whenmaking bread, like that shown in Figure 9.13, yeast cells produce CO2that forms bubbles in the dough.Eventually the heat of baking thebread kills the yeast and the bubblepockets are left to lighten the bread.You can do the activity in theMiniLab on this page to examine fer-mentation in apple juice.


Figure 9.13Alcoholic fermentation bythe yeast in a bread recipeproduces CO2 bubbles thatraise the bread dough.

Yeast andapple juice

Plastic pipette

Water

Test tube

Metalwashers

Purpose Students will observe the produc-tion of CO2 resulting from yeastfermenting sugar.Process Skillsobserve and infer, interpret data,experiment, analyze dataSafety PrecautionsHave students wear aprons andsafety goggles.Teaching Strategies■ Ask students to brainstorm andlist the uses of industrial alco-holic fermentation. Ask themwhich products (alcohol or CO2)of the process are important.Expected ResultsStudents will see gas bubblescoming from the yeast/applejuice mixture.Analysis

1. CO22. The rate would increase.3. Warm water increases the

metabolic rate of the yeast.4. Anaerobic, because no oxygen

is available in the bulb of thepipette covered with water.

Performance Have stu-dents prepare a summary of theMiniLab in their journals. Usethe Performance Task AssessmentList for Lab Report in PASC,p. 47. L2

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MiniLab 9-2MiniLab 9-2

Internet Address Book

Note Internet addressesthat you find useful in

the space below for quick reference.

VIDEODISCThe Infinite Voyage: The ChampionWithin, Physiology of Consistent

Performance (Ch. 5) 3 min. 30 sec.!7U`H"

Glycogen: Fuel for Muscles (Ch. 6) 5 min. 30 sec.!7_jJ"

Section AssessmentSection AssessmentSection Assessment1. Glycolysis produces 2 ATP molecules;

aerobic respiration, as many as 38.2. Alcoholic fermentation produces alco-

hol and carbon dioxide. Lactic acid fer-mentation produces lactic acid.

3. Most of the ATP is produced by the re-actions of the electron transport chain.

4. When oxygen is unavailable.5. Aerobic respiration occurs in the leg

muscles of both runners. The sprintermay build up more lactic acid and beout of breath because of an oxygendebt associated with the quick burst ofenergy.

6. Differences: Photosynthesis forms sug-ars and oxygen, uses water and CO2.Respiration uses oxygen to break down

sugar, forms water and CO2. Photo-synthesis uses light to form chemicalbond energy. Respiration uses chemi-cal bond energy to form ATP.Similarities: Both are complex reac-tions, require enzymes, occur in spe-cific organelles, and involve electrontransport chains.

243


Laboratory Manual, pp. 61-68

Reinforcement and StudyGuide, p. 40

Content Mastery, pp. 41,43-44

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1. Interpreting Observations Fromwhere did the bubbles of oxygenemerge? Why?

2. Making Inferences Explain howcounting bubbles measures therate of photosynthesis.

3. Using the Internet Make a graphof your data and data posted byother students with the rate ofphotosynthesis per minute plot-ted against the wavelength oflight you tested for both the con-trol and experimental setups.

Write a sentence or two explain-ing the graph.

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

Sharing Your DataSharing Your Data

Find this BioLab on theGlencoe Science Web

Site at www.glencoe.com/sec/science. Post your data in the data table providedfor this activity. Use the additional datafrom other students who tested wave-lengths other than those you tested toexpand your graph.

1. Construct a basic setup like theone shown opposite.

2. Create a data table to record your measurements. Be sure toinclude a column for each colorof light you will investigate and a column for the control experi-ment.

3. Place the Elodea plants in thebeaker, then completely cover the plants with water. Add someof the baking soda solution. The solution provides CO2 forthe aquarium plants. Be sure to use the same amount ofwater and solution for eachtrial.

4. Conduct a control experiment bydirecting the lamp (without colored cellophane) on the plant and notice when you see the bubbles.

5. Observe and record the numberof oxygen bubbles that Elodeagenerates in five minutes.

6. Repeat steps 4 and 5 with a pieceof colored cellophane. Recordyour observations.

7. Repeat steps 4 and 5 with a different color of cellophane andrecord your observations.

8. Go to the Glencoe Science Web Site at the address shownbelow to post your data.

PROCEDUREPROCEDURE

Bubbles observed in five minutes

Color 1 Color 2Control

Data Table

1. The bubbles emerged fromthe end of the stem of theElodea plant.

2. Oxygen is an end product ofphotosynthesis. As the rate ofphotosynthesis changes, sowill the rate at which oxygenis produced.

3. The rate for the control setupshould be the greatest andtherefore the highest line.The rates corresponding tocolored, filtered light will belower than the control.Results will vary dependingon the color of cellophanethe students use.

Portfolio Have studentswrite an evaluation of the lab.Their evaluations should includean overview of the experiment,data analysis, and conclusionstatements. Have them also writehypotheses about how photosyn-thesis might be affected if anothercondition, such as temperature,were changed. Use the Perfor-mance Task Assessment List forFormulating a Hypothesis inPASC, p. 21. L2

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ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

245


What factors influence photosynthesis?

INTERNETINTERNET

Oxygen is one of the products of photosynthesis. Because oxygen is only slightly soluble in water, aquatic plants such as Elodea

give off visible bubbles of oxygen as they carry out photosynthesis. By measuring the rate at which bubbles form, you can measure therate of photosynthesis.

ProblemHow do different wavelengths of

light a plant receives affect its rate ofphotosynthesis?

ObjectivesIn this BioLab, you will:■ Observe photosynthesis in an

aquatic organism.

■ Measure the rate of photosynthesis.■ Observe how various wavelengths

of light influence the rate of photo-synthesis.

■ Use the Internet to collect and com-pare data from other students.

Materials1000-mL beakerthree Elodea plantsstringwasherscolored cellophane, assorted colorslamp with reflector and 150-watt

bulb0.25% sodium hydrogen

carbonate (baking soda) solution

watch with second hand

Safety PrecautionsAlways wear goggles in the lab.

Skill HandbookUse the Skill Handbook if you need

additional help with this lab.

PREPARATIONPREPARATION

244

Time Allotment One class period

Process Skillsuse variables and controls, thinkcritically, observe and infer, col-lect data, interpret data

Safety PrecautionsStudents should always wear gog-gles in the lab. Be sure hands andwork areas are dry when handlingelectrical equipment and havestudents wash hands at the end ofthe lab.

Prepare sodium hydrogen car-bonate solution by mixing 2.5 gsodium hydrogen carbonate with1000 mL of water.

Alternative Materials■ If Elodea is unavailable, you can

use any other green aquaticplant.

■ Students can use the classroomclock if the second hand is visible.

PREPARATIONPREPARATION

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PROCEDUREPROCEDURE

Teaching Strategies■ Place the Elodea sprigs in a large bowl andplace them under a lamp for about 10 min-utes before students begin the lab. Thisreduces the time the students will wait tobegin seeing evidence of photosynthesis.■ You may wish to circulate through theroom during this activity to ensure that thesetups are constructed properly and that the

students are seeing evidence of photosyn-thesis.

Data and ObservationsStudents should record data under controlconditions and then under experimentalconditions for the same amount of time—atleast 5 minutes.

Sharing Your DataSharing Your Data

To navigate the InternetBioLabs, choose the

Biology: The Dynamics of Life icon at thesite. Click on the student site icon, then theBiolabs icon. The advantage of using theInternet for an experiment of this nature isthat students can collect considerably more

and varied data than they could collect ontheir own in the allotted time. They also gainthe experience of communicating scientificinformation using a technology that wasoriginally intended for the dissemination ofscientific knowledge.

INTERNETINTERNET INTERNETINTERNET


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Chapter 9 AssessmentChapter 9 Assessment

SUMMARYSUMMARY

Section 9.1

Section 9.2

Section 9.3

Main Ideas■ ATP is the molecule that stores energy for easy

use within the cell.■ ATP is formed when a phosphate group is

added to ADP. When ATP is broken down,ADP and phosphate are formed and energy isreleased.

■ ATP is the main link between energy-releasingand energy-using reactions.

Vocabulary(ADP) adenosine

diphosphate (p. 228)(ATP) adenosine

triphosphate (p. 228)

ATP in aMolecule

Main Ideas■ Photosynthesis is the process by which cells use

light energy to make carbohydrates. ■ Chlorophyll in the chloroplasts of plant cells

traps light energy needed for photosynthesis.■ The light reactions of photosynthesis produce

ATP and result in the splitting of water molecules.

■ The reactions of the Calvin cycle make carbohydrates using CO2 along with ATP andhydrogen from the light reactions.

VocabularyCalvin cycle (p. 234)chlorophyll (p. 232)electron transport chain

(p. 232)light-dependent

reactions (p. 231)light-independent

reactions (p. 231)NADP+ (p. 233)photolysis (p. 234)photosynthesis (p. 231)pigments (p. 232)

Main Ideas■ Cellular respiration is the process by which cells

break down carbohydrates to release energy. ■ Cellular respiration takes place in mitochondria,

uses oxygen, and yields many more ATPs thando anaerobic processes.

■ Energy can be released anaerobically byglycolysis followed by alcoholic or lacticacid fermentation.

Vocabulary aerobic respiration

(p. 237)alcoholic fermentation

(p. 242)anaerobic respiration

(p. 237)cellular respiration

(p. 237)citric acid cycle (p. 238)glycolysis (p. 237)lactic acid fermentation

(p. 242)

Getting Energyto Make ATP

CHAPTER 9 ASSESSMENT 247

1. Which of the following is a product of theCalvin cycle?a. carbon dioxide c. oxygenb. NADP+ d. FADH2

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS 2. ________ processes require oxygen, whereas________ processes do not.a. anaerobic—aerobicb. aerobic—anaerobicc. photolysis—aerobicd. aerobic—respiration

Photosynthesis:Trapping theSun’s Energy

247

SummarySummary statements can be used bystudents to review the major con-cepts of the chapter.

Using the VocabularyTo reinforce chapter vocabulary, usethe Content Mastery Booklet andthe activities in the Interactive Tutorfor Biology: The Dynamics of Life onthe Glencoe Science Web Site:www.glencoe.com/sec/science

1. b2. b

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS


All ChapterAssessment

questions and answers have beenvalidated for accuracy and suitabil-ity by The Princeton Review.


Chapter Assessment, pp. 49-54MindJogger VideoquizzesComputer Test BankBDOL Interactive CD-ROM, Chapter 9

quiz

In photosynthesis, light energy is converted into chemical energy. To begin the process,

light is absorbed by colorful pigment molecules contained in chloroplasts.

Apigment is a substance that can absorb thevarious wavelengths of visible light. You

can observe the colors of these wavelengths byletting sunlight pass through a prism to create a“rainbow,” or spectrum, that has red light on oneend, violet on the other, and orange, yellow,green, and blue light in between.

Every photosynthetic pigment is distinctivein that it absorbs certain wavelengths in the visi-ble light spectrum.

Chlorophylls a and b The principal pigmentof photosynthesis is chlorophyll. Chlorophyllexists in two forms designated as a and b. Chloro-phyll a and b both absorb light in the violet toblue and red to red-orange parts of the spectrum,although at somewhat different wavelengths.These pigments also reflect green light, which iswhy plant leaves appear green.

When chlorophyll b absorbs light, it transfersthe energy it acquires to chlorophyll a, whichthen feeds that energy into the chemical reac-tions that lead to the production of ATP andNADP. In this way, chlorophyll b acts as an“accessory” pigment by making it possible forphotosynthesis to occur over a broader spectrumof light than would be possible with chlorophylla alone.

Carotenoids and phycobilins Carotenoids and phycobilins are other kinds of accessory pig-ments that absorb wavelengths of light differentfrom those absorbed by chlorophyll a and b, andso extend the range of light that can be used forphotosynthesis.

Carotenoids are yellow-orange pigments.They are found in all green plants, but theircolor is usually masked by chlorophyll.


ConnectionChemistryChemistry

Connection Plant Pigments

How do you think accessory pigments may haveinfluenced the spread of photosynthetic organ-isms into diverse habitats such as the deep sea?

To find out more about pig-ments, visit the Glencoe Science

Web Site. www.glencoe.com/sec/science

CONNECTION TO BIOLOGYCONNECTION TO BIOLOGY

Carotenoids are also found in cyanobacteria andin brown algae. A particular carotenoid calledfucoxanthin gives brown algae their characteris-tic dark brown or olive green color.

Phycobilins are blue and red. Red algae gettheir distinctive blood-red coloration from phy-cobilins. Some phycobilins can absorb wave-lengths of green, violet, and blue light that pene-trate into deep water. One species of red algaethat contains these pigments is able to live atocean depths of 269 meters (884 feet). Thealgae’s pigments absorb enough of the incrediblyfaint light that penetrates to this depth—only0.0005 percent of what is available at the water’ssurface—to power photosynthesis.

Pigments color cyanobacteria(above) and red algae (inset).

Magnification: 1630�

246

Purpose Students should recognize therole that pigments such aschlorophyll play in the process ofphotosynthesis.

BackgroundThere are far more chlorophyllmolecules in a green leaf thancarotenoids, and for most of thegrowing season, chlorophyllmasks the presence of thoseaccessory pigments. In theautumn, however, chlorophyllbreaks down and the other pig-ments in leaves are visible as “fallcolors.” The cause of this chloro-phyll breakdown is not com-pletely understood, but it seemsto be tied to the gradual reduc-tion in daylight that takes place assummer ends.

Teaching Strategies■ Have students examine live (orpreserved) specimens of green,brown, and red algae to observethe difference in pigments.

■ Melanin is a pigment in ani-mals that absorbs ultraviolet radi-ation and protects skin and othertissues from sun damage. Havestudents research melanin alongwith a plant pigment and createposters that compare the two.

Connection to BiologyAccessory pigments have made itpossible for photosyntheticorganisms to use a broader rangeof the visible light spectrum, andin so doing, survive in placeswhere the amount or quality ofvisible light is minimal.

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ConnectionChemistryChemistry

Connection

Internet Address Book

Note Internet addresses that you find useful in the spacebelow for quick reference. VIDEOTAPE

MindJogger VideoquizzesChapter 9: Energy in a CellHave students work in groups as they playthe videoquiz game to review key chapterconcepts.




CHAPTER 9 ASSESSMENT 249

25. If you were planning on studying the com-pounds that could possibly be the source ofthe oxygen released during photosynthesis,which compounds would you need to consider?

26. Formulating Hypotheses Elodea sprigs wereplaced under a white light, and the rate ofphotosynthesis was measured by counting thenumber of oxygen bubbles per minute for tenminutes. Predict the rate of photosynthesis ifa piece of red cellophane were placed overthe white light.

27. Observing and Inferring Yeast cells must beforced to ferment by placing them in an envi-ronment without any oxygen. Why wouldthe yeast cells carry out aerobic respirationrather than fermentation when oxygen is pre-sent?

28. Recognizing Cause and Effect A windowplant native to the desert of South Africa hasleaves that grow almost entirely undergroundwith only the transparent tip of the leaf pro-truding above the soil surface. Suggest howthis adaptation aids the survival of this plant.

29. Concept Mapping Make a concept mapusing the following vocabulary terms: cellularrespiration, glycolysis, citric acid cycle, electron transport chain.

THINKING CRITICALLYTHINKING CRITICALLY

ASSESSING KNOWLEDGE & SKILLSASSESSING KNOWLEDGE & SKILLS

Yeast cells and sucrose were placed in a testtube, and the tube was then plugged. Theyeast–sucrose mixture incubated for 24hours. Gas bubbles began to rise to the topof the tube. After 24 hours, no sucrose wasleft in the solution.

Interpreting Data Use the graph to answerthe questions below.1. What process was the yeast using to

digest the sucrose at the beginning ofthe experiment?a. photosynthesisb. anaerobic respirationc. aerobic respirationd. light-dependent reactions

2. Which of the following would be left inthe solution after 24 hours?a. sucrose c. oxygenb. lactic acid d. ethyl alcohol

3. What gas would be found in the top ofthe tube after the incubation period?a. carbon dioxide c. hydrogenb. oxygen d. nitrogen

4. Making a Table Construct a table fromthe graph showing the oxygen levels andcarbon dioxide levels.

For additional review, use the assessmentoptions for this chapter found on the Biology: TheDynamics of Life Interactive CD-ROM and on theGlencoe Science Web Site.www.glencoe.com/sec/science

CD-ROM

Gas

leve

l (m

L)

0 6 12

Hours

18 24

10

5

O2 CO2

Yeast Cell Respiration

are the steps of

2.

4.

1. 3.

which takes place in mitochondria

249

25. carbon dioxide and water26. Photosynthetic rate would

decrease. Although the cello-phane transmits red light, itwould cut down the light in theblue end of the spectrum that isalso used in photosynthesis.

27. Aerobic respiration is a muchmore efficient process and pro-duces many more ATPs persugar molecule.

28. This adaptation conserves waterwhile allowing the plant to getlight for photosynthesis,thereby solving the main prob-lem of desert plants.

29. 1. Glycolysis; 2. Citric acid cycle;3. Electron transport chain; 4.Cellular respiration

THINKING CRITICALLYTHINKING CRITICALLY


1. c2. d3. a4. Student tables should be

consistent with the infor-mation in the graph.


3. During all energy conversions, some of theenergy is converted to ________.a. carbon dioxide c. heatb. water d. sunlight

4. Four molecules of glucose would give a netyield of ________ ATP following glycolysis.a. 8 c. 4b. 16 d. 12

5. In which of the following structures do thelight-independent reactions of photosynthe-sis take place?a. c.

b. d.

6. What is the first process in the cell to beaffected by anaerobic conditions?a. citric acid cycleb. fermentationc. glycolysisd. electron transport chain

7. Which molecule provides the most accessiblesource of energy for cell organelles?a. glucose c. starchb. ATP d. carbon dioxide

8. Which of the following uses no energy?a. glycolysis c. light reactionsb. Calvin cycle d. muscle contraction

9. Which of the following transports high-energy electrons in photosynthesis?

a. NADP+ c. FADb. NAD+ d. ATP

10. When yeast ferments the sugar in a breadmixture, what is produced that causes thebread dough to rise?a. carbon dioxide c. ethyl alcoholb. water d. oxygen

11. Plants must have a constant supply of________ for photosynthesis, but they pro-vide ________ for cellular respiration.

12. ________ is the first molecule to provide elec-trons for photosynthesis.

13. The ________ membrane is the site of photo-synthesis, whereas the ________ is the site forcellular respiration.

14. ________ is the process by which electronsare restored to chlorophyll after photosyn-thesis.

15. ________ acts as a source of CO2 in cellularrespiration.

16. ________ occurs in the inner membrane ofthe mitochondrion.

17. In fermentation, pyruvic acid can form________ or ________ in addition to NAD+.

18. ATP stores energy because the three________ have a negative charge and they________ each other.

19. ________ produces muscle soreness, whereas________, another type of fermentation, pro-duces ethyl alcohol.

20. ________ such as chlorophyll are the chemi-cal substances that give color to plants.

21. Why would human muscle cells containmany more mitochondria than skin cells?

22. How are cellular respiration and photosyn-thesis complementary processes?

23. What happens to sunlight that strikes a leafbut is not trapped by photosynthesis?

24. What might happen to Earth’s atmosphere ifphotosynthesis suddenly stopped?

APPLYING MAIN IDEASAPPLYING MAIN IDEAS

248 CHAPTER 9 ASSESSMENT

TEST–TAKING TIPTEST–TAKING TIP

Take 5 and Stay Sharp Wanting to perform well on your exam is praise-worthy. But if you study for long periods of time,you could actually end up hurting your chancesfor a good score. Remember to take frequentshort breaks in your studies to keep your mind

248

3. c4. a5. d6. d7. b8. b9. a

10. a11. carbon dioxide; oxygen12. chlorophyll13. thylakoid; mitochondrion14. Photolysis15. Citric acid cycle16. Electron transport chain17. lactic acid; ethanol18. phosphates; repel19. Lactic acid fermentation; alco-

holic fermentation20. Pigments

21. During physical activity, musclecells must release energy at ahigher rate than skin cells.

22. Photosynthesis stores energy,whereas respiration releasesenergy, and the products of oneprocess are the reactants of theother process.

23. Other pigments in the plantabsorb some of the light ofother wavelengths and pass theenergy to chlorophyll for use inphotosynthesis. The remaininglight that is not trapped isreflected or absorbed as heat.

24. Possible answer: The amount ofoxygen in the atmospherewould start to decrease becauseit would be used up in respira-tion and not replaced.

APPLYING MAIN IDEASAPPLYING MAIN IDEAS



Organic CompoundsCarbohydrates are chemical compounds

made up of carbon, hydrogen, and oxygen mole-cules. Common carbohydrates include sugars,starches, and cellulose. Lipids, known as fats andoils, contain a glycerol backbone and three fattyacid chains. Proteins are a combination of aminoacids connected by peptide bonds.

Eukaryotes andProkaryotes

All cells are surrounded by a plasma mem-brane. Eukaryotic cells contain membrane-boundstructures within the cell called organelles. Cellswithout internal membrane-bound structures arecalled prokaryotic cells.

The Life of a Cell

251

BIODIGESTBIODIGEST

Polysaccharides

A polysaccharide is a type of carbohydratemade up of a chain of monosaccharides.

Amino acids canbe joined withpeptide bonds toform proteins.

A eukaryoticcell containsmembrane-boundorganelles.

A prokaryotic celldoes not containmembrane-boundorganelles.

Organelles

Lipids are made up of aglycerol backbone and threefatty acid chains.

Glycerol

Fatty acid chains



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Portfolio Have studentscut out pictures of trees frommagazines and place them in theirportfolios. Then have them writeabout the tree from a cellularpoint of view. They shouldinclude details such as whetherthe cells of the trees are eukary-otic or prokaryotic, a list oforganelles that may be present,information about cells and phot-synthesis, ideas on cellular growthand reproduction, and cellulardifferentiation within the tree.Then have the students write acomparison with an animal cellusing the same information.PP

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BIODIGESTBIODIGEST

The Chemistry of LifeAlthough you are studying biology, chemistry

is fundamental to all biological functions.Understanding some of the basic concepts ofchemistry will enhance your understanding of thebiological world.

Elements and AtomsEvery substance in and on Earth is a combina-

tion of elements. An atom, the smallest compo-nent of an element, is formed by layers of elec-trons around a nucleus made of protons and neu-trons. Atoms come together to form molecules.

FOCUS ON HISTORYFOCUS ON HISTORY

In the 1600s, Anton van Leeuwenhoekwas the first person to view living

organisms through a microscope.Another scientist, Robert Hooke, namedthe structures cells. Two hundred yearslater, several scientists, includingMatthias Schleiden, Theodor Schwann,and Rudolph Virchow continued tostudy animal and plant tissues under themicroscope. Conclusions from all scien-tists were combined to form the celltheory:

1. All organisms are composed of one ormore cells.

2. The cell is the basic unit of organization oforganisms.

3. All cells come from preexisting cells.

The Cell Theory

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The Life of a CellAll organisms are made up of cells, and

each cell is like a complex, self-contained machine that can perform all of the life func-tions of the cell. Yet as small as they are, all of the mechanisms and processes of these little machines are not fully known, and scientists continue to unravel the marvelous mysteries of the living cell.

For a preview of the cell unit, study this BioDigest before you read the chapters.After you have studied the cell chapters, you can use the BioDigest to review the unit.

BIODIGESTBIODIGEST

VITAL STATISTICSVITAL STATISTICS

Carbon IsotopesIsotopes of carbon contain different numbersof neutrons.Carbon 12: six protons and six neutronsCarbon 13: six protons and seven neutronsCarbon 14: six protons and eight neutrons

van Leeuwenhoek mighthave viewed microorgan-isms like these found in adroplet of pond water.

Cells are microscopic machines

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250

National Science Education Standards:UCP.1, UCP.2, UCP.3, UCP.5,B.3, B.6, C.1, C.5, F.1, G.1, G.3

PreparePurposeThis BioDigest can be used as anintroduction to or as an overviewof the structure and function ofthe cell. If time is limited, youmay wish to use this unit sum-mary to teach about the cell inplace of the chapters in the Cellunit.

Key ConceptsStudents will learn that chemistryis an integral component of livingorganisms. According to the celltheory, the cell is the basic unit oforganization of all living matter.This means that even a complexorganism, such as a tree or anelephant, is made up of cells.Students will learn that the struc-ture and function of a cell and itsparts are similar, even for cellsthat serve very different func-tions. The concepts of how a celltransforms energy from the sunand food sources and how a cellreproduces will also be described.

1 FocusBellringer Display an overhead transparencyof a eukaryotic cell. Point outeach of the organelles and askstudents to identify the functionsof each organelle.

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BIODIGESTBIODIGEST

MultipleLearningStyles

Look for the following logos for strategiesthat emphasize different learning modalities.

Kinesthetic Meeting IndividualNeeds, p. 253Visual-Spatial Portfolio, p. 252;Microscope Activity, p. 252, 253Intrapersonal Project, p. 254

Linguistic Biology Journal, p. 252; Check for Understanding,

p. 255; Extension, p. 255


Bring in food items to demon-strate organic compounds. Apotato or bread can demon-strate carbohydrates, meat candemonstrate proteins, andvegetable oil or shortening candemonstrate lipids. Combinethis experience with a molecu-lar model of a lipid and relatethe model to the example lipidand to the overall structure ofthe plasma membrane.

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Assessment PlannerAssessment Planner

Portfolio AssessmentAssessment, TWE, p. 251

Performance AssessmentAssessment, TWE, p. 252

Knowledge AssessmentBioDigest Assessment, SE, p. 255

Skill AssessmentAssessment, TWE, p. 255

VIDEODISCThe Infinite Voyage Unseen Worlds,Studying the Basic Building Blocks:

The Atom (Ch. 9) 2 min.!7~$G"The Scanning Tunneling Microscope:

Observing Atomic Particles(Ch. 10) 2 min.!8$.J"

VIDEODISCSTV: The CellViewing the Cell

Early Pioneers - Unit 138 sec.

Cell Theorists - Unit 11 min. 15 sec.

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ProphaseTelophase

Anaphase

Interphase

Metaphase

Diffusion and OsmosisThe selectively permeable plasma membrane

allows only certain substances to cross. Diffusionis the movement of a substance from an area ofhigher concentration to an area of lower concen-tration. Diffusion of water across a selectively per-meable membrane is called osmosis.

Simple diffusion across a membrane occurs by random movement. Facilitated diffusionrequires proteins to bind and help move mole-cules across the membrane. Active transportrequires energy to move molecules across a concentration gradient.

MitosisAs cells grow, they reach a size

where the plasma membrane can-not transport enough nutrientsand wastes to maintain cellgrowth. At this point, the cellundergoes mitosis and divides.

Prior to mitosis is a period ofintense metabolic activity calledinterphase. The first stage of mito-sis is prophase, when the dupli-cated chromosomes condense andthe mitotic spindle forms on thetwo opposite ends of the cell. Thechromosomes line up in the centerof the cell during metaphase andslowly separate during anaphase.In telophase the nucleus dividesfollowed by cytokinesis, which sep-arates the daughter cells.

The Life of a Cell

253

BIODIGESTBIODIGEST

Carrier protein

Higher concentrationof ions

Ions Lower concentrationof ions Energy

Membrane proteins can transport substances against the concentrationgradient in active transport.

During the stages of mitosis, chromosomes are replicated and separatedinto two daughter cells.


Cellular EnvironmentsIsotonic solution: same number of mole-cules inside and outside the cellHypotonic solution: more molecules insidethe cell; water enters the cellHypertonic solution: fewer moleculesinside the cell; water leaves the cell


253

DemonstrationLinguistic Use this demon-stration to simulate osmosis

in hypotonic, isotonic, and hy-pertonic solutions. Fill threepieces of dialysis tubing with red15% sucrose solution. Tie thetop of each dialysis bag around ahollow piece of glass tubing.Clamp each bag/tubing apparatusto a ring stand and place in oneof three solutions: distilled water(hypotonic), 15% clear sucrosesolution (isotonic), and a 30%sucrose solution (hypertonic). Atthe beginning of the demonstra-tion, mark the initial level of thered sucrose in the glass tubing. Atregular intervals, such as the endof each class period, again markthe level of the red sucrose solu-tion. Use the changes in volumeof the three dialysis bags to quan-tify osmosis in hypotonic, iso-tonic, and hypertonic solutions.

Microscope ActivityVisual-Spatial Set up a seriesof microscopes with pre-

pared slides of onion root tipdemonstrating the stages of mito-sis. Have students look at theslides before discussing the stagesof mitosis. After naming and dis-cussing the stages, have studentslook at the slides again and askthem to explain what they see.P

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BIODIGESTBIODIGEST

Carbohydrate

Phospholipidbilayer

ProteinFatty acid tail

Phosphate head

Cell Organelles The organelles of a cell work together to

carry out the functions necessary for cell survival.

Plasma Membrane According to the fluid mosaic model, the

plasma membrane is formed by two layers ofphospholipids with the fatty acid chains back-to-back; the phosphate groups face the externalenvironment, and proteins are embedded in themembrane.

Control of Cell FunctionsThe nucleus contains the master plans for

proteins, which are then produced by organellescalled ribosomes. The nucleus also controls cellu-lar functions.

Assembly, Transport, and Storage

The cytoplasm suspends the cell’s organelles,including endoplasmic reticulum, Golgi appara-tus, vacuoles, and lysozomes. The endoplasmicreticulum and Golgi apparatus transport andmodify proteins.

Energy Transformers Chloroplasts are found in plant cells and

capture the sun’s light energy so it can be transformed into useable chemical energy.Mitochondria are found in both animal and plant cells and transform the food you eat into a useable energy form.

Support and LocomotionA network of microfilaments and micro-

tubules attach to the plasma membrane to givethe cell structure. Cilia are short, numerous pro-jections that move like a wave. Flagella arelonger projections that move in a whiplike fash-ion to propel a cell.

The Life of a Cell

252

BIODIGESTBIODIGEST

The plasma membrane is composed ofa lipid bilayer with embedded proteins.

Plasma membrane

Mitochondrion

Nucleus

Chloroplast

Cell wall

Vacuole

Golgi apparatus

Ribosomes

Roughendoplasmic

reticulum

Magnification: 46 000�Magnification: 11 250�

Plant cell Animal cell

252

Microscope ActivityVisual-Spatial Set up micro-scopes with slides demon-

strating animal and plant cells.Have students look at the cellsand identify differences betweenthe two cells.

Help the students by explain-ing that animal cells have centri-oles and plant cells do not.Centrioles play a role during celldivision and in the formation ofmicrotubules. Also explain thatplant cells contain a cell wall out-side the plasma membrane andonly one or two large vacuolesthat store water. Make sure thestudents understand that animalcells also have vacuoles, but thereare more of them and they aresmaller than those found inplants.

Performance Have stu-dents look at slides of animal andplant cells and identify the struc-tures.


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BIODIGESTBIODIGEST


OrganellesLinguistic Have students write aparagraph about how the cellular

organelles act like a factory to produceproteins and energy. They should includehow organelles regulate the intake ofnecessary materials and the export ofproducts and wastes.

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PortfolioPortfolio

The Plasma MembraneVisual-Spatial In their portfolios,have students draw a plasma mem-

brane. They should include phospholipidsshowing the polar head and fatty acidtails forming a bilayer with the heads andtails properly oriented. Have them includeseveral transmembrane proteins.

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Visually ImpairedKinesthetic Tie pairs of sockstogether in the middle to simulate

chromosomes undergoing mitosis. Createa series of cells and place the pairs ofsocks in the appropriate places to mimicthe stages of mitosis. Have visuallyimpaired students manipulate the sockchromosomes.

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Exploration: Parts of the CellDisc 1BioQuest: Cellular PursuitDisc 1

VIDEODISCThe Secret of LifeCell Membranes: Membranes and

Transport

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Exploration: Phases of MitosisDisc 1

The Life of a Cell

255

BIODIGESTBIODIGEST


ATP production for each molecule of glucoseGlycolysis: produces a net gain of two ATP, two NADH, and

two H+Acetyl-CoA formation: produces two NADHCitric acid cycle (Krebs cycle): produces two ATP, six NADH,

and two FADHElectron transport chain: produces 32 ATP from NADH and

FADHLactic acid fermentation: produces two ATP

BIODIGEST ASSESSMENTBIODIGEST ASSESSMENT

Understanding Main Ideas1. What is a starch?

a. a lipid c. a proteinb. a carbohydrate d. a peptide

2. The building blocks of proteins are________.a. fatty acids c. amino acidsb. monosaccharides d. glycerol

3. A cell that does not contain internal, mem-brane-bound structures is a ________.a. prokaryoteb. eukaryotec. yeast celld. a cell with organelles

4. The organelle that produces proteins is the________.a. nucleus c. ribosomesb. lysozome d. vacuole

5. What structure is part of the cell’s skele-ton?a. Golgi apparatusb. nucleusc. endoplasmic reticulumd. microfilaments

6. The movement of a substance across theplasma membrane against the concentra-tion gradient by binding to a protein is________.a. facilitated transportb. osmosisc. simple diffusiond. active transport

7. What structure is involved in movement?a. cilia c. vacuoleb. lysozomes d. chloroplasts

8. The stage of mitosis when the chromatidsseparate and move to opposite sides ofthe cell is ________.a. prophase c. anaphaseb. metaphase d. telophase

9. The organelle that transforms light energyto ATP is ________.a. mitochondrionb. endoplasmic reticulumc. chloroplastd. nucleus

10. Which is involved in capturing light energyfrom the sun?a. light-dependent reactionsb. Citric acid cyclec. Calvin cycled. light-independent reactions

Thinking Critically1. Compare and contrast the functions of

chloroplasts and mitochondria in energytransformation.

2. Describe the organelles of a eukaryoticcell.

3. Relate transport across the plasma mem-brane in isotonic, hypertonic, and hypo-tonic solutions to changes in cell shapedue to water movement across the mem-brane.

Energy from ATP

255

3 AssessCheck for Understanding

Linguistic Ask students toname as many organelles as

they can and identify the functionof each.

ReteachPut up an overhead of the stagesof mitosis and have studentsidentify the stages and describethe events.

ExtensionLinguistic Have studentsresearch melanoma and pre-

pare a presentation illustrating itsoccurrence and treatment. Havethem also develop a preventionplan.

Skill Ask students todescribe what will happen to acell’s volume if it is placed in ahypotonic, isotonic, or hypertonicenvironment.

4 CloseDiscussionDiscuss how a plant cell obtainsenergy and stores it and how ananimal cell obtains energy andtransforms it to a usable form forcell organelles.

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BIODIGESTBIODIGEST

2. Most organelles of a eukaryotic cell are sur-rounded by a membrane. This membraneallows very different chemical reactions tobe carried out in a cell at the same time.

3. In an isotonic solution, the concentration ofsolutes on both sides of the membrane isthe same, so there will be no net move-ment across the membrane and the cellshape will not change.

254

Classroom ActivityUse play money to demonstratethe analogy that ATP is the cur-rency for energy. Assign a cost toseveral objects in the classroomand point out that some items“cost” more than others. Havestudents purchase these objectsusing large bills such as $100s or$500s to demonstrate that largedenominations must be brokendown to smaller amounts. Thenrelate the cost to the energyexpense to perform cellular activ-ity. An example of an inexpensivetransaction in a cell is transport-ing two Na+ ions outside of thecell. An example of an expensiveactivity is making a protein.Relate that glucose is a largedenomination of energy currencythat cells break down into smalleramounts to fuel cellular activity.

Visual LearningDisplay overheads of the Calvincycle and the citric acid cycle.Explain that the cycles can berepeated again and again to pro-duce different products.

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BIODIGESTBIODIGEST

P R O J E C TCancer Facts Research

Intrapersonal Have studentsresearch one type of cancer that

can be prevented by a lifestyle such asnot smoking, sun avoidance, exercise, or diet. Have students present theirreport to the class.

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BIODIGEST ASSESSMENTBIODIGEST ASSESSMENT

Understanding Main Ideas1. b 4. c 7. a 10. a2. c 5. d 8. c3. a 6. d 9. c

Thinking Critically1. Chloroplasts trap light energy and store it

by producing complex sugars. Mitochondriabreak down sugars to release ATP. Both areinvolved in energy production for the cell.

In a hypertonic solution, there is a greater con-centration of solutes outside the cell, there is anet movement of water from the cell into thesurrounding fluid, and the cell size will shrink.In a hypotonic solution, there is a greater con-centration of solutes inside the cell; therefore,water will flow into the cell and the cell sizewill increase.

VIDEODISCThe Secret of LifeCell Energy: Cell

Respiration

!:_MHkBD"Resource ManagerResource Manager

Reinforcement and StudyGuide, pp. 41-42

Content Mastery, pp. 45-48L1

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Energy in a Cell Adenosine triphosphate (ATP) is the most

commonly used source of energy in a cell. Twoorganelles are involved in forming ATP fromother sources of energy.

Chloroplasts in plant cells harvest energyfrom the sun’s rays and convert it to ATP using

light-dependent reactions. Light-independentreactions convert energy into carbohydrates suchas starch through the Calvin cycle.

Mitochondria, found in both plant and ani-mal cells, convert food energy into ATP through aseries of chemical reactions that include glycoly-sis, the citric acid cycle, and the electron transportchain.

FOCUS ON HEALTHFOCUS ON HEALTH

Cancer is one condition that can result when acell can no longer control the rate of mitosis.

Cancer may be due to factors inside the cell, such asenzyme overproduction or production at the wrongtime. Cancer can also be a result of environmentalfactors.

In recent years, much emphasis has been placedon healthy lifestyles that can help prevent cancer.Eating diets rich in fruits and vegetables, exercisingregularly, and quitting or avoiding smoking can allhelp reduce the incidence of cancer.

Cancer

The Life of a Cell

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BIODIGESTBIODIGEST

In chloroplasts, the Calvin cycle allows thesun’s energy to be stored as carbohydratesfor later use.

In mitochondria, the citric acidcycle allows the breakdown offood sources to form ATP.

This melanoma is an exampleof skin cancer.


Magnification:70 875�

Documents

Chapter 9: Energy in a Cell...Section 9.1 BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES Use with Chapter 9, Section 9.1 How is each of these organisms using energy? In