Photosynthesis
- Created by: Catr08
- Created on: 27-03-21 12:26
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Stages of photosynthesis:
Light-dependent stage occurs in the thylakoids and converts light energy into chemical energy (ATP+NADH)
Light-independent stage occurs in the stroma and uses the chemical energy to produce carbon compounds
1. Light-dependent stage
1.1 Non-cyclic phosphorylation
- Chlorophyll in photosystems I and II (PSI and PSII) absorbs light which triggers the release of energised electrons (photoactivation) --> electrons are excited
- Electrons from PSI reduce NADP to form NADPH
- Electrons from PSII pass through the electron transport chain before replacing electrons from PSI
- The transport chain produces ATP (photophosphorylation)
- PSII electrons pass through the electron chain, lose energy, translocates H+ ions to thylakoid
- this creates an electrochemical gradient or proton motive force
- Chemiosmosis: H+ ions return to the stroma via ATP synthase
- This catalyzes ATP
- Electrons lost by PSII are replaced by water (photolysis)
- H2O --> 2H++2e-+1/2O2
1.2 Cyclic phosphorylation
- Only chlorophyll in Photosystem I are activated by light
- The electrons move through an electron transport chain before returning to their original location (i.e. cyclic)
- The transport chain…
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