Biology Biomolecules MDCAT 2017
PMDC Verified Question 134 of 142
Backbone of amino acid comprises of:
A
-NH2 Group
B
-COOH group
C
C-C-N
D
-H group
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: C-C-N
Concept:

The polypeptide backbone forms a continuous, repeating structural chain along the length of a protein.

Solution:

  • Every single amino acid contains an amino group (nitrogen), an alpha-carbon, and a carboxyl carbon.


  • When they bond linearly via peptide bonds, the continuous repeating sequence making up the unbranched structural "spine" of the protein is precisely N-C-C (or C-C-N).


Why other options are incorrect:

  • The individual -NH2 and -COOH groups represent the functional ends of a monomer, but the actual polymerized backbone is the repeating C-C-N sequence itself.

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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