MCAT Biochemistry Question 4: Answer and Explanation

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Question: 4

4. Which of these statements concerning peptide bonds is FALSE?

  • A. Their formation involves a reaction between an amino group and a carboxyl group.
  • B. They are the primary bonds that hold amino acids together.
  • C. They have partial double bond character.
  • D. Their formation involves hydration reactions.

Correct Answer: D

Explanation:

Peptide bonds are the primary covalent bond between the amino acids that make up proteins, making choice (B) incorrect. They involve a condensation reaction between the amino group of one amino acid and the carboxyl group of an adjacent amino acid, eliminating choice (A). The peptide bond has a partial double bond character because the double bond can resonate between C=O and C=N. Thus, the peptide bond has a partial double bond character and exhibits limited rotation, eliminating choice (C). By process of elimination, choice (D) is false: formation of the peptide bond is a condensation reaction—specifically a dehydration reaction involving the loss of water—not a hydration reaction involving the addition of water.

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