In a polypeptide, you would expect a peptide bond to link which pair of atoms between two amino acids?

• A. The $\alpha$-carbon of one amino acid to the $\alpha$-carbon of another amino acid
• B. The side-chain (R-group) carbon of one amino acid to the side-chain (R-group) carbon of another amino acid
• C. The carbonyl carbon of one amino acid to the amino nitrogen of another amino acid
• D. The carboxyl oxygen of one amino acid to the carboxyl carbon of another amino acid

Answer: (C)

Verified step by step guidance

1. Recall that a peptide bond is a covalent bond formed during protein synthesis between two amino acids.
2. Identify the functional groups involved: each amino acid has an amino group (-NH2) and a carboxyl group (-COOH) attached to the alpha-carbon.
3. Understand that the peptide bond forms specifically between the carbonyl carbon (C=O) of the carboxyl group of one amino acid and the nitrogen (N) of the amino group of the next amino acid.
4. Recognize that this bond formation involves a dehydration reaction, where a molecule of water is released as the bond forms.
5. Therefore, the peptide bond links the carbonyl carbon of one amino acid to the amino nitrogen of another amino acid.