Biology Bioenergetics NUMS 2022
PMDC Verified Question 43 of 67
In the process of photosynthesis, water acts as:
A
Proton acceptor
B
Electron donor
C
\( CO_2 \) reducer
D
\( CO_2 \) accepter
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Electron donor
Concept:

In the light-dependent reactions of photosynthesis, water undergoes photolysis to replace the electrons lost by Photosystem II.

Solution:

  • Light energy splits water into \( 2H^+ \), \( \frac{1}{2}O_2 \), and releases electrons.
  • These electrons are donated to the oxidized chlorophyll molecules of the reaction center, making water the ultimate electron donor in non-cyclic photophosphorylation.


Why other options are incorrect:

  • Water donates protons (\( H^+ \)) to the thylakoid lumen rather than accepting them.
  • \( NADPH \) acts as the direct reducer of \( CO_2 \), not water.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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