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UNIT 5: Photosynthesis and Respiration
BIG IDEA: Energy is produced and released by making and breaking
chemical bonds
Think About It:
• With your partner, come up with a list of activities that you do that requires energy
• What gives us energy?
Obtaining Energy
• Autotrophs• Organisms that are capable of
making food (energy) from simple inorganic substances
• EX: green plants, algae
Two Types of Autotrophs
• 1. Photoautotrophs: use carbon dioxide and light energy to drive reactions needed to make food
Next type…
• 2. Chemoautotrophs: utilize inorganic chemicals for the energy to drive food making reactions
Obtaining Energy
• Heterotrophs• Organisms that cannot make their
own food (energy) and must depend on other plants or animals as food source (energy)
• Examples: Humans, dogs, cats
Photosynthesis
• Process of capturing energy of sunlight and transforming it into chemical energy
• CO2 + H2O----glucose + O2
Photosynthesis• Two stages
– Light reactions- light energy is converted into chemical energy of two intermediate molecules
– Calvin cycle-Organic molecules are formed from CO2
Photosynthesis
• Sunlight, sometimes called white light, is a form of energy that travels in waves
• Wavelength: the distance between the crest of one wave and the crest of the next wave
Visible Light Spectrum
• Depends on wavelength• Blue: 380 (nm)• Green: 500 (nm)• Yellow 560 (nm)• Light red: 600 (nm)• Darker red: 750 (nm)
Photosynthesis• Pigments: absorb light• EX: a red object absorbs all the visible
colors of the spectrum except red which is reflected and gives the object the red color
Types of Photosynthetic Pigments
a. Chlorophylls: absorb red and blue light, appear green
b. Carotenes: absorb blue, appear orange
c. Xanthophylls: appear yellow, may not be used to absorb light
• The color of an egg yolk is from the xanthophyll carotenoids lutein and zeaxanthin
The color of an egg yolk is from the xanthophyll carotenoids lutein and zeaxanthin
Parts of the Chloroplast
• Thylakoid- Membrane of the thylakoid contains photosynthetic pigments; flattened sacs
• Site of the light reactions
Parts of the Chloroplast
• Grana- Stacks of thylakoids• Stroma-Region b/t grana
– Site of the light independent reactions
Photosynthesis Reactions
• Light Dependent Reactions-energy from light makes the reaction happen
• Light Independent Reactions- Doesn’t need the energy from light to make the reaction happen but they do need products of the light reaction to proceed.
Light Dependent Reactions- In the Chloroplast
• Pigments in the photosynthetic membranes absorb light (pigments are located in Photosystem I & II
• When the light hits the chlorophyll in Photosystem II the electrons become excited and jump up.
• The electrons are captured by the electron transport chain.
• We need to replace the electrons that are lost so we steal some from water . This breaks the water molecule apart forming H+ and O
• As we transport electrons down the chain we use their energy to produce ATP
• The electrons now go to Photosystem I and it loses electrons to NADP+ to make it NADPH.
The final products of the light reaction
• At the end of the light reaction we have made
1. NADPH
2. ATP
3. O2
Light independent reaction ( Calvin Cycle)
• A. Use CO2 , ATP, NADPH
• B. Uses products from light reaction (Light is not necessary for this reaction)
• C. Location stroma
Steps in Light Independent Reaction:
• 6 CO2 reacts with the sugar, ribulose phophate (RuBP)sugar called phosphoglycerate (PGA)
• PGA12 phosphoglyceraldehyde (PGAL)
• NADPH and ATP from light reaction provide energy for this step
Steps in Light Independent Reaction (con’t)
• PGAL does 2 things:
a. Makes more RuBP to continue cycle (requires 10 PGAL to do this)
b. Form 1 glucose (requires 2 PGAL)
Photosynthesis
includes
of
take place intakes place in uses
to produce to produce
use
Light-dependentreactions
Calvin cycle
Thylakoidmembranes Stroma NADPHATPEnergy from
sunlight
ATP NADPH O2 ChloroplastsHigh-energysugars
Section 8-3
Concept Map
Chloroplast
Light
O2Sugars
CO2
Light-Dependent Reactions
CalvinCycle
NADPH
ATP
ADP + P
NADP+Chloroplast
Section 8-3
Figure 8-7 Photosynthesis: An Overview
Factors Affecting Photosynthesis
• Four main types:
a. Light intensity
b. Temperature
c. Water
d. Mineral availability
Cellular Respiration
• Release of the energy stored in food
• Occurs in the inside of the cells of both autotrophs and heterotrophs
Adenosine Triphosphate (ATP)
• Energy released during cellular respiration is stored as ATP
• Consists of adenine, ribose and three phosphates
How is energy stored in ATP?
• Energy is stored in the bonds. Once a bond breaks (causing ATP to lose a phosphate group), there is a release of energy.
Adenosine diphosphate or (ADP)
• Two phosphate groups, adenine, and ribose
• Where would the energy be in ADP
Two Types of Cellular Respiration
Aerobic Respiration:• Occurs in presence of oxygen• Occurs in the mitochondria• Produces about 36 ATP
Second Type of Cellular Respiration
Anaerobic Respiration:• Occurs without oxygen• Occurs in the cytoplasm• Produces 2 ATP
Which type of cellular respiration is more efficient?
• Aerobic because it produces more ATP (more energy)
Two types of Anaerobic Respiration:
• 1. Alcoholic Fermentation: yeast produces alcohol
• 2. Lactic Acid Fermentation: muscles produces lactic acid when they don’t have enough oxygen