Biology Biomolecules ETEA 2022
PMDC Verified Question 92 of 142
Proteins are macromolecules formed of units known as amino acids. The amino acids in which the variable group (R) is represented by an H atom is:
A
Lysine
B
Phenylalanine
C
Glycine
D
Alanine
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Glycine
Concept:

The chemical identity and properties of each amino acid are dictated solely by its unique 'R' side-chain.

Solution:

  • Glycine is the simplest, most basic amino acid found in nature.


  • Its variable R-group consists of just a single Hydrogen (H) atom.


  • Because of this tiny side chain, glycine can comfortably fit into incredibly tight structural turns within protein folding architectures, such as the collagen triple helix.


Why other options are incorrect:

  • Alanine: R-group is a methyl group (\(-CH_3\)).


  • Phenylalanine: R-group contains a large, bulky benzyl ring.


  • Lysine: R-group is a long, positively charged hydrocarbon chain ending in an amino group.

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