Biology Bioenergetics SZABMU 2022
PMDC Verified Question 55 of 67
The element whose electrons are excited during light reactions of photosynthesis is:
A
Carbon
B
Hydrogen
C
Magnesium
D
Nitrogen
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Magnesium
Concept:

Photosynthetic pigments must be able to absorb light energy and readily release high-energy electrons.

Solution:

  • The core of the chlorophyll molecule is a porphyrin ring containing a central Magnesium (\( Mg \)) atom.
  • When sunlight hits chlorophyll, it is the electrons associated with this central magnesium atom and the alternating double bonds of the porphyrin ring that become highly excited and are expelled to a primary electron acceptor.


Why other options are incorrect:

  • Carbon, hydrogen, and nitrogen form the structural backbone of the ring, but magnesium plays the central role in electron excitation and release.

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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