Photosynthesis Photosynthesis Electron Transport Chain

Question 1

Which photosystem in the thylakoid membrane is responsible for splitting water molecules to release oxygen?

Accepted Answer

Photosystem II (PSII)

Answer

Photosystem II contains the oxygen-evolving complex that catalyzes the splitting of water into protons, electrons, and molecular oxygen as a byproduct.

Question 2

What molecule accepts electrons from the iron-sulfur centers of Photosystem I during the light reactions?

Accepted Answer

Ferredoxin

Answer

Ferredoxin is a small iron-sulfur protein that accepts electrons from PSI and transfers them to NADP+ reductase (FNR) for NADPH production.

Question 3

Which manganese-containing protein complex carries out the oxidation of water in Photosystem II?

Accepted Answer

Oxygen-evolving complex (OEC)

Answer

The oxygen-evolving complex contains a cluster of four manganese ions that catalyze the oxidation of two water molecules, releasing four electrons, four protons, and one O2.

Question 4

What is the primary role of plastoquinone (PQ) in the photosynthetic electron transport chain?

Accepted Answer

Shuttle electrons and protons from PSII to the cytochrome b6f complex

Answer

Plastoquinone is a mobile lipid-soluble carrier that picks up electrons and protons from PSII and delivers them to the cytochrome b6f complex, contributing to the proton gradient.

Question 5

Which metal ion is absolutely required for the function of the oxygen-evolving complex in Photosystem II?

Accepted Answer

Manganese (Mn)

Answer

The oxygen-evolving complex requires a cluster of four manganese ions to catalyze the stepwise removal of electrons from water, accumulating oxidizing equivalents until O2 is released.

Photosynthesis Practice Test

Photosynthesis Practice Test

Photosynthesis Photosynthesis Electron Transport Chain