incorporating CO 2 into organic acids • Stomata close during the day, and CO 2 is released from organic acids and used in the Calvin cycle Light Light Reactions: Photosystem II Electron transport chain NADP ADP + P i RuBP 3-Phosphoglycerate Calvin H 2 O CO 2 Figure 10.22 Photosystem I Electron transport chain ATP NADPH Cycle G3P Starch (storage) Sucrose (export) Chloroplast O 2
10 The Importance of Photosynthesis • The energy entering chloroplasts as sunlight gets stored as chemical energy in organic compounds • Sugar made in the chloroplasts supplies chemical energy and carbon skeletons to chemical energy and carbon skeletons to synthesize the organic molecules of cells • Plants store excess sugar as starch in structures such as roots, tubers, seeds, and fruits • In addition to food production, photosynthesis produces the O 2 in our atmosphere You should now be able to: 1. Describe the structure of a chloroplast 2. Describe the relationship between an action spectrum and an absorption spectrum 3. What is non cyclic flow of electrons and its importance 4. What is cyclic flow of electrons and its importance 5. Describe the similarities and differences between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts 6 Describe the role of ATP and NADPH in the 6. Describe the role of ATP and NADPH in the Calvin cycle 7. Describe the major consequences of photorespiration 8. Describe two important photosynthetic adaptations that minimize photorespiration
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