BioInteractive Photosystems I and II 1 — Questions and Answers
Question 1: What is the primary electron donor in Photosystem II?
- NADPH
- Water (Correct answer)
- Plastocyanin
- Ferredoxin
Correct answer: Water
Photosystem II oxidizes water molecules to extract electrons, releasing O2 as a byproduct through the oxygen-evolving complex.
Question 2: What is the designation of the reaction center chlorophyll in Photosystem II?
- P700
- P680 (Correct answer)
- P650
- P720
Correct answer: P680
The reaction center of PSII contains a special chlorophyll a molecule that absorbs light maximally at 680 nm, designated P680.
Question 3: What is the designation of the reaction center chlorophyll in Photosystem I?
- P680
- P650
- P700 (Correct answer)
- P730
Correct answer: P700
Photosystem I contains a special chlorophyll a molecule that absorbs light maximally at 700 nm, designated P700.
Question 4: In what order do electrons flow through the two photosystems during non-cyclic electron flow?
- PSI → PSII
- PSII → PSI (Correct answer)
- PSI → PSII → PSI
- PSII → PSII → PSI
Correct answer: PSII → PSI
In linear (non-cyclic) electron flow, electrons move from water through PSII, then through the electron transport chain to PSI, where they are ultimately used to produce NADPH.
Question 5: Which photosystem contains the oxygen-evolving complex that splits water?
- Photosystem I
- Both photosystems equally
- Photosystem II (Correct answer)
- Neither photosystem
Correct answer: Photosystem II
Photosystem II contains the oxygen-evolving complex (OEC) that catalyzes the oxidation of water, extracting electrons and releasing O2.
Question 6: Where are both Photosystem I and Photosystem II located within the chloroplast?
- Outer envelope membrane
- Stroma
- Thylakoid membrane (Correct answer)
- Inner envelope membrane
Correct answer: Thylakoid membrane
Both PSI and PSII are integral membrane protein complexes embedded in the thylakoid membranes, where the light reactions take place.
Question 7: What is the primary function of the antenna complex (light-harvesting complex) in photosystems?
- Split water molecules
- Produce ATP via chemiosmosis
- Capture light energy and transfer it to the reaction center (Correct answer)
- Synthesize NADPH directly
Correct answer: Capture light energy and transfer it to the reaction center
Antenna complexes contain arrays of chlorophyll and accessory pigment molecules that absorb photons and funnel excitation energy to the reaction center via resonance energy transfer.
BioInteractive Photosystems I and II 1
What is the primary electron donor in Photosystem II?