Question

What type of covalent bonds link the amino acids in a protein ?

• A. Peptide bonds
• B. Hydrogen bonds
• C. Glycosidic bonds
• D. Ester bonds

Hint:

To remember biopolymer linkages:
- Proteins (amino acids) $\rightarrow$ Peptide bonds.
- Carbohydrates (sugars) $\rightarrow$ Glycosidic bonds.
- Lipids (fatty acids + glycerol) $\rightarrow$ Ester bonds.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Proteins are biological macromolecules composed of linear chains of amino acid residues.
These amino acids are linked together sequentially through specific covalent chemical bonds formed during protein synthesis (translation).

Step 3: Detailed Explanation:
Let us analyze the chemical linkage between amino acids:
- A Peptide Bond (amide bond) is formed via a condensation reaction between the carboxyl group ($-\text{COOH}$) of one amino acid and the amino group ($-\text{NH}_2$) of the adjacent amino acid, releasing a molecule of water ($H_2O$):
\[ -CO-NH- \]
This strong covalent link forms the backbone of the polypeptide chain.
- Let us review why the other options are incorrect:
- Hydrogen Bonds: Weak, non-covalent electrostatic attractions responsible for folding the polypeptide chain into secondary structures ($\alpha$-helices and $\beta$-sheets), but they do not link the amino acid backbone covalently.
- Glycosidic Bonds: Covalent bonds that link monosaccharide units together to form carbohydrates (polysaccharides).
- Ester Bonds: Covalent linkages formed between an acid and an alcohol, typical of lipid structures (triacylglycerols).
Therefore, peptide bonds covalently link amino acids in proteins.

Step 4: Final Answer:
The covalent bonds that link amino acids in a protein are Peptide bonds.