1. Photosynthesis Dark Reaction
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2. Review Two Stages of Photosynthesis
Capturing energy from sunlight to make ATP and NADPH.
Storing energy in carbohydrates
ATP and NADPH powering carbon fixation.
Chloroplast Structure
Internal membranes organized into sacs of thylakoids and stacked in grana.
Semiliquid fluid (stroma) surrounds thylakoid membrane.
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3. Leaf Organization
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4. Photosystems I and II “Z” Scheme
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5. Two Photosystems Work Together
Two-stage photosystem referred to as non-cyclic phosphorylation.
Photosystem II acts first.
High energy electrons generated by photosystem II used to synthesize ATP, and then passed to photosystem I to drive NADPH production.
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7. Light and Dark Reactions occur in different parts of the chloroplast
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8. Carbon Fixation- The Calvin Cycle
CO2 attaches to ribulose bisphosphate (RuBP).
Splits to form 2 three-carbon molecules of phosphoglycerate (PGA).
Also called C3 photosynthesis.
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9. Photorespiration-Why photosynthesis is not very efficient
Photorespiration incorporates O2 into ribulose1,5-bisphosphate instead of CO2.
Under normal conditions, 20% of photosynthetically-fixed carbon is lost to photorespiration.
Loss rises as temperature increases.
Why does this happen?
Oxygen competes with CO2 for RuBP
21% of the atmosphere is O2, only 0.03% is CO2
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10. C4 Plants are Adapted to Hot Climates
In hot climates, plants close their stomata to reduce water loss
This reduces the amount of CO2 that can be taken in even more!
C4 photosynthesis produces a four carbon compound which does not go through photorespiration.
C4 plants conduct the Light Reaction in mesophyll cells and the Calvin Cycle in bundle sheath cells.
Creates high levels of CO2
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12. Crassulacean Acid Metabolism (CAM) plants
CAM plants are adapted to hot environments
Open stomata during the night and close them during the day to minimize water loss.
Use C4 during the night and C3 during the day.
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13. Raven - Johnson - Biology: 6th Ed
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14. Copyright © McGraw-Hill Companies Permission
required for reproduction or display
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