Question 1

The splitting of water (photolysis) that releases O₂, protons and electrons is associated with:

Accepted Answer

Photosystem II. Water splitting occurs on the inner thylakoid side associated with PS II, replenishing its electrons.

Question 2

The products of the light reaction that are used in the dark reaction are:

Accepted Answer

ATP and NADPH. The light reaction produces assimilatory power (ATP + NADPH) used to fix CO₂ in the Calvin cycle.

Question 3

In NON-cyclic photophosphorylation, electrons flow from ______ and both ATP and NADPH are produced:

Accepted Answer

PS II → PS I (Z-scheme), with water as the electron source. The Z-scheme: PS II → electron carriers → PS I → NADP⁺; water donates electrons and NADPH is formed.

Question 4

CYCLIC photophosphorylation involves only ______ and produces ______ (no NADPH, no O₂):

Accepted Answer

PS I; ATP only. In cyclic flow, electrons return to PS I; only ATP is made, with no water splitting or NADPH.

Question 5

The reaction-centre chlorophyll of PS I and PS II absorb maximally at, respectively:

Accepted Answer

P700 and P680. PS I peaks at 700 nm (P700) and PS II at 680 nm (P680) — hence their names.

Question 6

Cyclic photophosphorylation also occurs when only wavelengths beyond ______ are available (only PS I functional):

Accepted Answer

680 nm. Beyond 680 nm only PS I works, so electron flow is cyclic, producing only ATP (the "red drop"/enhancement context).

Light Reaction & Photophosphorylation — NEET Biology MCQs with Solutions

Questions with solutions