Apentix/AP Biology/Unit 3: Cellular Energetics/Question
AP Biologyhardmcq1 pt

Why does linear electron flow in photosynthesis use two photosystems in series?

A.The second photosystem mainly doubles the ATP produced for each absorbed photon
B.Photosystem I lacks chlorophyll and must borrow excitation from photosystem II
C.Two successive light excitations raise electrons enough to reduce NADP+
D.The second photosystem pumps oxygen made from water out of the thylakoid

Explanation

Core Concept

Electrons removed from water begin at too low an energy state to reduce NADP+ after a single light-driven excitation. Photosystem II and photosystem I provide two successive energy boosts, producing the characteristic Z-scheme of linear electron flow.

Correct Answer

CTwo successive light excitations raise electrons enough to reduce NADP+

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