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PhotosynthesiPhotosynthesiss

Energy & Life

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Overview of Overview of PhotosynthesiPhotosynthesi

ss

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AutotrophsAutotrophsPlants and Plants and some other some other types of types of organisms that organisms that contain contain chlorophyllchlorophyll are are able to use able to use light energy light energy from the sunfrom the sun to to produce food.produce food.

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AutotrophsAutotrophs• Autotrophs Autotrophs

include include organismsorganisms that make that make their own foodtheir own food

• Autotrophs Autotrophs can use the can use the sun’s energy sun’s energy directlydirectly

EuglenaEuglena

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HeterotrophsHeterotrophs• Heterotrophs Heterotrophs

are are organisms organisms that can NOT that can NOT make their make their own foodown food

• Heterotrophs Heterotrophs can NOT can NOT directly use directly use the sun’s the sun’s energyenergy

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EnergyEnergy• Energy Takes Many Energy Takes Many

Forms such as Forms such as light, light, heat, electrical, heat, electrical, chemical, mechanicalchemical, mechanical

• Energy can be Energy can be changed from changed from one one form to anotherform to another

• Energy can be stored Energy can be stored in chemical bonds & in chemical bonds & then released laterthen released later

Candles release energy as HEAT & LIGHTCandles release energy as HEAT & LIGHT

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ATP – Cellular EnergyATP – Cellular Energy• Adenosine TriphosphateAdenosine Triphosphate• Contains two, high-energy Contains two, high-energy

phosphate bondsphosphate bonds• Also contains the nitrogen base Also contains the nitrogen base

adenine & a ribose sugaradenine & a ribose sugar

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ADPADP• Adenosine DiphosphateAdenosine Diphosphate• ATP releases ATP releases energyenergy, a , a free free

phosphate,phosphate, & & ADPADP when cells when cells take energy from ATPtake energy from ATP

One phosphate bond has been removed

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Sugar in ADP & ATPSugar in ADP & ATP

•Called ribose

•Pentose sugar

•Also found on RNA

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Importance of ATPImportance of ATP

Principal Compound Used To Store Energy In Living Organisms

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Releasing Energy From Releasing Energy From ATPATP

• ATP is constantly being ATP is constantly being used and used and remade by cellsremade by cells

• ATP provides all of the energy ATP provides all of the energy for for cell activitiescell activities

• The high energy phosphate The high energy phosphate bonds can be bonds can be BROKENBROKEN to to release release energyenergy

• The process of releasing ATP’s The process of releasing ATP’s energy & reforming the molecule energy & reforming the molecule is called is called phosphorylationphosphorylation

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Releasing Energy From Releasing Energy From ATPATP

• AddingAdding A A Phosphate Phosphate Group To ADP Group To ADP stores Energy in stores Energy in ATPATP

• RemovingRemoving A A Phosphate Phosphate Group From ATP Group From ATP Releases Energy Releases Energy & forms ADP& forms ADP

Loose

Gain

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Cells Using Biochemical Cells Using Biochemical EnergyEnergy

Cells Use ATP For:• Active transport• Movement• Photosynthesis• Protein Synthesis• Cellular

respiration• All other cellular

reactions

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More on ATPMore on ATP• Cells Have Enough ATP To Cells Have Enough ATP To

Last For A Last For A Few SecondsFew Seconds• ATP must ATP must constantlyconstantly be be

mademade• ATP ATP Transfers Energy Transfers Energy

Very WellVery Well• ATP Is ATP Is NOTNOT Good At Good At

Energy StorageEnergy Storage

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GlucoseGlucose•Glucose is a Glucose is a

monosaccharidemonosaccharide•CC66HH1212OO66

•One Molecule of glucose One Molecule of glucose Stores Stores 90 Times90 Times More More Chemical Energy Than Chemical Energy Than One Molecule of ATPOne Molecule of ATP

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History of History of Photosynthesis & Photosynthesis & Plant PigmentsPlant Pigments

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PhotosynthesisPhotosynthesis• Involves the Use Of light Energy to Involves the Use Of light Energy to

convert convert Water (HWater (H220)0) and and Carbon Carbon Dioxide (CODioxide (CO22)) into into Oxygen (OOxygen (O22)) and and High Energy CarbohydratesHigh Energy Carbohydrates (sugars, e.g. Glucose) & Starches(sugars, e.g. Glucose) & Starches

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The Photosynthesis The Photosynthesis EquationEquation

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Investigating Investigating PhotosynthesisPhotosynthesis

•Many Scientists Have Many Scientists Have Contributed To Contributed To Understanding Understanding PhotosynthesisPhotosynthesis

•Early ResearchEarly Research Focused On Focused On The The Overall ProcessOverall Process

•Later ResearchersLater Researchers Investigated The Detailed Investigated The Detailed Chemical PathwaysChemical Pathways

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Early Questions on Early Questions on PlantsPlants

Several Centuries Ago, Several Centuries Ago, The Question Was:The Question Was:

Does the increase in Does the increase in mass of a plant come mass of a plant come from the air? The soil? from the air? The soil?

The Water?The Water?

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Van Helmont’s Van Helmont’s Experiment 1643Experiment 1643

• Planted a Planted a seedseed into into A pre-measured A pre-measured amount of soil and amount of soil and wateredwatered for 5 years for 5 years

• Weighed Plant & Weighed Plant & Soil.Soil. Plant Was 75 Plant Was 75 kg, Soil The Same.kg, Soil The Same.

• Concluded Mass Concluded Mass Came From WaterCame From Water

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Priestley’s Experiment Priestley’s Experiment 17711771

• Burned Candle In Bell Jar Until It Went Out.

• Placed Sprig Of Mint In Bell Jar For A Few Days.

• Candle Could Be Relit And Burn.

• Concluded Plants Released Substance (O2) Necessary For burning.

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Ingenhousz’s Ingenhousz’s Experiment 1779Experiment 1779

Repeated Priestly experiment with & without Repeated Priestly experiment with & without sunlightsunlight

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Results of Ingenhousz’s Results of Ingenhousz’s ExperimentExperiment

• Showed That Priestley’s Showed That Priestley’s Results Only Occurred In Results Only Occurred In The Presence Of The Presence Of SunlightSunlight..

• Light Was Necessary For Light Was Necessary For Plants To Produce The Plants To Produce The “Burning Gas” or “Burning Gas” or oxygenoxygen

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Julius Robert Mayer Julius Robert Mayer 18451845

Proposed That Proposed That Plants can Plants can Convert Convert Light Light Energy Into Energy Into ChemicalChemical EnergyEnergy

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Samuel Ruben & Martin Samuel Ruben & Martin KamenKamen19411941

Used Isotopes Used Isotopes To Determine To Determine That The That The OxygenOxygen Liberated In Liberated In PhotosynthePhotosynthesis sis Comes Comes From WaterFrom Water

KAMENKAMEN

RUBINRUBIN

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Melvin Calvin 1948Melvin Calvin 1948•First to trace the path First to trace the path that that carbon (COcarbon (CO22)) takes takes in forming in forming GlucoseGlucose•Does Does NOTNOT require require sunlightsunlight•Called the Called the Calvin CycleCalvin Cycle or or Light Independent Light Independent ReactionReaction•Also knownAlso known as the as the Dark Dark ReactionReaction

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Rudolph Marcus 1992Rudolph Marcus 1992•Studied the Studied the Light Light Independent Independent ReactionsReactions•First to First to describe the describe the Electron Electron transport transport ChainChain

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The Photosynthesis The Photosynthesis EquationEquation

PigmentsPigments• In addition to water,

carbon dioxide, and light energy, photosynthesis requires Pigments

•Chlorophyll is the primary light-absorbing pigment in autotrophs

•Chlorophyll is found inside chloroplasts in the thylakoids

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Light and Light and PigmentsPigments

• Energy From The Sun Enters Earth’s Biosphere As Photons

•Photon = Light Energy Unit

• Light Contains A Mixture Of Wavelengths

•Different Wavelengths Have Different Colors

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Light & PigmentsLight & Pigments• Different pigmentsDifferent pigments absorb absorb

different different wavelengthswavelengths of light of light• Photons of light Photons of light “excite”“excite”

electrons in the plant’s electrons in the plant’s pigmentspigments

• Excited electrons carry the Excited electrons carry the absorbed energyabsorbed energy

• Excited electrons move to Excited electrons move to HIGHERHIGHER energy levels energy levels

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PigmentsPigmentsThere are 4 main There are 4 main

types of pigment types of pigment molecules:molecules:

Chlorophyll aChlorophyll aChlorophyll bChlorophyll bXanthophyllXanthophyllCarotenesCarotenes

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Chlorophyll a and bChlorophyll a and b

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Chlorophyll aChlorophyll a•Found in all Found in all plants, plants, algae, & cyanobacteriaalgae, & cyanobacteria•Makes photosynthesis Makes photosynthesis possiblepossible•Participates Participates directlydirectly in in the Light Reactionsthe Light Reactions•Can Can accept energyaccept energy from from chlorophyll bchlorophyll b

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Chlorophyll bChlorophyll b• Chlorophyll b is an Chlorophyll b is an

accessory pigmentaccessory pigment• Chlorophyll b acts Chlorophyll b acts

indirectlyindirectly in in photosynthesis by photosynthesis by transferring the light it transferring the light it absorbs to chlorophyll absorbs to chlorophyll aa

• Like chlorophyll a, it Like chlorophyll a, it absorbs red & blue light absorbs red & blue light and and REFLECTS GREENREFLECTS GREEN

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The The Biochemical Biochemical ReactionsReactions

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It Begins with Sunlight!It Begins with Sunlight!

Flow of Energy

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Photoautotrophs Absorb Photoautotrophs Absorb Light EnergyLight Energy

Objectives• Summarize how energy is captured from sunlight in

the first stage of photosynthesis.• Analyze the function of electron transport chains in

the second stage of photosynthesis.• Relate the Calvin cycle to carbon dioxide fixation in

the third stage of photosynthesis.• Identify three environmental factors that affect the

rate of photosynthesis.

Key Terms• Pigment• Chlorophyll• Carotenoid• Thylakoid• Electron Transport

Chain

• NADPH• Carbon Dioxide

Fixation• Calvin Cycle

Where does Photosynthesis occur?• Plants/Autotrophs – produce their own food

(glucose)• Process called photosynthesis• Mainly occurs in the leaves:

a. stoma - poresb. mesophyll cells-chloroplasts

found in this area

StomaMesophyllCell

Chloroplast

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Structure of the Structure of the ChloroplastChloroplast

• Double membraneDouble membrane organelle organelle• Outer membrane Outer membrane smoothsmooth• Inner membraneInner membrane forms forms

stacks of connected sacs stacks of connected sacs called called thylakoidsthylakoids

• Thylakoid stack is called the Thylakoid stack is called the granungranun (grana-plural) (grana-plural)

• Gel-like material around Gel-like material around grana called grana called stromastroma

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Inside A ChloroplastInside A Chloroplast

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The 2 Stages of Photosynthesis• Stage 1-Light ReactionStage 1-Light Reaction

– Energy is captured from sunlight by chlorophyll Energy is captured from sunlight by chlorophyll and other pigments present.and other pigments present.

– Light energy is converted to chemical energy as Light energy is converted to chemical energy as water is split, which is temporarily stored in ATP water is split, which is temporarily stored in ATP & the energy carrier molecule NADPH and O& the energy carrier molecule NADPH and O2 2

gas is given offgas is given off• Stage 2 -Light Independent Reaction/Dark Stage 2 -Light Independent Reaction/Dark

Reaction/Calvin CycleReaction/Calvin Cycle– The chemical energy stored in ATP & NADPH The chemical energy stored in ATP & NADPH

powers the formation of organic compounds from powers the formation of organic compounds from the combination of RuBP and the COthe combination of RuBP and the CO2 2 to to eventually makes Glucose.eventually makes Glucose.

Stages of Photosynthesis

RuBP

CellusloseCelluslose

The Photosynthesis Equation

6CO2 + 6H20 C6H12O6 + 6O2Light

Carbon Dioxide

Water Sugars Oxygen(High Energy)

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Photosynthesis Photosynthesis OverviewOverview

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Function of the StromaFunction of the Stroma•Light IndependentLight Independent

(DARK,CALVIN) (DARK,CALVIN) reactions occur herereactions occur here

•ATP usedATP used to make to make carbohydrates like carbohydrates like glucoseglucose

•Location of the Location of the Calvin Calvin CycleCycle

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Light Dependent Light Dependent ReactionReaction

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Light Dependent Light Dependent ReactionReaction

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The Calvin CycleThe Calvin Cycle

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Factors Affecting the Factors Affecting the Rate of PhotosynthesisRate of Photosynthesis• Amount of available Amount of available

waterwater• TemperatureTemperature• Amount of available Amount of available

light energylight energy• pHpH• Quantity and Quantity and

combination of combination of pigmentspigments

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