8489978
Description
Flashcards by Becky Saunders, updated more than 1 year ago
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Created by Becky Saunders
about 7 years ago
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| Question | Answer |
| Where does the Light-Dependent Reaction take place? | In the thylakoid membranes of the chloroplast |
| What photosystems are used? | Photosystem II which absorbs light at 680nm, followed by photosystem I which absorbs light at a higher wavelength of 700nm. |
| 1. What happens in Non-Cyclic Photophosphorylation in PSII part 1? | 1. Light energy is absorbed by PSII & excites electrons in chlorophyll 2. Electrons move to a higher energy level, & are released from the reaction centre of PSII. 3. The electrons pass through an electron transport chain. |
| 2. What then happens during Photolysis? | 1. As excited electrons from chlorophyll leave PSII, they must be replaced 2. Light energy splits water into protons, electrons & oxygen 3. Electrons are released by photolysis & replace those lost from PSII. |
| 3. What happens in Non-Cyclic Photophosphorylation in PSII part 2? | 4. Excited electrons lose energy as they pass through the ETC 5. This energy is used to pump H+ ions into the thylakoid via proton pumps in the thylakoid membrane 6. This creates a proton gradient, with a greater concentration of H+ in the thylakoid than in the stroma 7. H+ ions therefore move back across the membrane via an enzyme called ATP synthase. The energy from this movement forms ATP from substrate-level phosphorylation of ADP+Pi |
| 4. What happens in Non-Cyclic Photophosphorylation in PSI? | 1. Light energy hits PSI & excites the electrons in chlorophyll at the reaction centre of PSI 2. Electrons move to a higher energy level 3. They are released again into the ETC & ATP is produced by chemiosmosis. 4. Electrons lost from the reaction centre at PSI are replaced by those that have just travelled along the first ETC following PSII. 5. Electrons leaving the ETC following PSI are accepted by NADP as well as an H+ ion - forming reduced NADP. |
| 5. What happens in Cyclic Photophosphorylation? | 1. Only PSI is involved 2. Excited electrons leave PSI & pass through electron carriers in the ETC 3. Instead of being used to form reduced NADP, the electrons are passed back to the chlorophyll molecule via electron carriers. (However, ATP is still made by chemiosmosis) |
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