BioInteractive Light Reactions of Photosynthesis 2 — Questions and Answers
Question 1: What process uses the proton gradient across the thylakoid membrane to synthesize ATP?
- Chemiosmosis (Correct answer)
- Glycolysis
- Oxidative phosphorylation
- Substrate-level phosphorylation
Correct answer: Chemiosmosis
Chemiosmosis drives ATP synthase using the H+ gradient built up across the thylakoid membrane.
Question 2: Which complex in the thylakoid membrane splits water and releases O2?
- Oxygen-evolving complex (Correct answer)
- ATP synthase
- NADP+ reductase
- Cytochrome b6f
Correct answer: Oxygen-evolving complex
The oxygen-evolving complex (OEC) at Photosystem II catalyzes the splitting of water.
Question 3: What happens to electrons after they leave Photosystem II?
- They pass through the electron transport chain to Photosystem I (Correct answer)
- They combine with CO2
- They are used to split water
- They directly produce glucose
Correct answer: They pass through the electron transport chain to Photosystem I
Electrons flow from Photosystem II through the cytochrome b6f complex and plastocyanin to Photosystem I.
Question 4: What role does plastoquinone play in the light reactions?
- Electron carrier between Photosystem II and cytochrome b6f (Correct answer)
- Light absorber
- ATP producer
- Carbon fixer
Correct answer: Electron carrier between Photosystem II and cytochrome b6f
Plastoquinone shuttles electrons and protons from Photosystem II to the cytochrome b6f complex.
Question 5: What is the function of ferredoxin in the light reactions?
- Transfer electrons from Photosystem I to NADP+ reductase (Correct answer)
- Split water molecules
- Absorb red light
- Synthesize ATP
Correct answer: Transfer electrons from Photosystem I to NADP+ reductase
Ferredoxin accepts electrons from Photosystem I and passes them to NADP+ reductase to reduce NADP+ to NADPH.
Question 6: How many photons are required to produce one O2 molecule from water splitting?
- 8 (Correct answer)
- 2
- 4
- 6
Correct answer: 8
Eight photons (4 per photosystem × 2 photosystems) drive the reactions needed to split two water molecules and release one O2.
BioInteractive Light Reactions of Photosynthesis 2
What process uses the proton gradient across the thylakoid membrane to synthesize ATP?