BioInteractive Photosystems I and II 2

Question 1

Which protein immediately accepts electrons from Photosystem I before NADPH is produced?

Accepted Answer

Ferredoxin

Answer

Ferredoxin is the immediate electron acceptor from PSI; it then passes electrons to the enzyme NADP+ reductase (FNR), which reduces NADP+ to NADPH.

Question 2

What reduced molecule is produced when NADP+ accepts electrons in Photosystem I?

Accepted Answer

NADPH

Answer

NADP+ reductase uses electrons from ferredoxin and protons from the stroma to reduce NADP+ to NADPH, the key electron carrier used in the Calvin cycle.

Question 3

Which mobile electron carrier transfers electrons from Photosystem II to the cytochrome b6f complex?

Accepted Answer

Plastoquinone

Answer

Plastoquinone (PQ) is a lipid-soluble molecule embedded in the thylakoid membrane that picks up electrons and protons from PSII and shuttles them to the cytochrome b6f complex.

Question 4

Which copper-containing protein transfers electrons from the cytochrome b6f complex to Photosystem I?

Accepted Answer

Plastocyanin

Answer

Plastocyanin is a small, water-soluble copper protein located in the thylakoid lumen that carries electrons from the cytochrome b6f complex to PSI.

Question 5

How many water molecules must be split by the oxygen-evolving complex to release one molecule of O2?

Accepted Answer

Two

Answer

Two water molecules (2H2O) are oxidized to release four electrons, four protons (H+), and one O2 molecule: 2H2O → 4H+ + 4e− + O2.

BioInteractive - Photosynthesis BioInteractive Test Practice Test

BioInteractive - Photosynthesis BioInteractive Test Practice Test

BioInteractive Photosystems I and II 2