Biology Biomolecules MDCAT 2016
PMDC Verified Question 138 of 142
Phosphodiester bond is:
A
P-O-C-P-O-C
B
C-O-P-O-C
C
C-O-P
D
C-C-O-P
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: C-O-P-O-C
Concept:

The nucleic acid backbone relies on bridging multiple atoms to link independent nucleotides together.

Solution:

  • A phosphodiester bond connects the 3' carbon of one sugar to the 5' carbon of the next sugar via a central phosphate group.


  • Structurally, it forms two distinct ester linkages branching off the central phosphorus.


  • The linear atomic sequence through this bridge is precisely: Carbon (from sugar 1) - Oxygen - Phosphorus - Oxygen - Carbon (from sugar 2).


  • This is perfectly represented by the formula C-O-P-O-C.


Why other options are incorrect:

  • C-O-P / C-C-O-P: These represent only a single ester linkage (like attaching a phosphate to just one sugar), not the diester bridge linking two.


  • P-O-C-P-O-C: Incorrect atomic repetition; a single phosphate (P) bridges the gap.

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 Biomolecules 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