Chemistry Macromolecules / Biochemistry MDCAT 2018
PMDC Verified Question 41 of 47
Amino acids react with each other such that -COOH group of one amino acid reacts with the another amino acid to give a condensed structure as shown below. What is the name of circled part of this structure?

- CO - NH -
A
Ester linkage
B
Azide linkage
C
Peptide linkage
D
Carbide linkage
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Peptide linkage
Concept:

Proteins are formed through dehydration condensation reactions between amino acids, resulting in a specific amide bond.

Formula:

$$ \text{R-COOH} + \text{H}_2\text{N-R'} \rightarrow \text{R-CO-NH-R'} + \text{H}_2\text{O} $$

Solution:

  • The reaction between the carboxylic acid group (\( \text{-COOH} \)) of one amino acid and the amino group (\( \text{-NH}_2 \)) of a second amino acid releases a water molecule.
  • The resulting \( \text{-CO-NH-} \) bond linking the two amino acids is biochemically referred to as a peptide linkage (or peptide bond).


Why other options are incorrect:

Ester linkages (\( \text{-COO-} \)) are found in lipids, linking fatty acids to glycerol. Azide (\( \text{-N}_3 \)) and carbide are entirely different chemical groups not found in the protein backbone.

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