Biology Bioenergetics UHS 2024
PMDC Verified Question 15 of 67
In Calvin cycle \( CO_2 \) reacts with RuBP to produce _.
A
3-PGA
B
G3P
C
6-Carbon unstable intermediate
D
1,3 bisphosphoglycerate
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: 6-Carbon unstable intermediate
Concept:

The very first step of the Calvin cycle is carbon fixation, catalyzed by the enzyme RuBisCO.

Solution:

  • A single molecule of \( CO_2 \) (1 carbon) is covalently attached to Ribulose-1,5-bisphosphate (RuBP) (5 carbons).
  • This immediately produces a 6-carbon unstable intermediate compound.
  • Because it is so highly unstable, this 6-carbon molecule instantly breaks in half to form two molecules of 3-phosphoglycerate (3-PGA).


Why other options are incorrect:

  • While 3-PGA is the first stable product, the direct initial reaction produces the transient 6-carbon intermediate.

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.

Previous Question All Bioenergetics MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App