Question

The primary structure of a protein is due to

• A. $-\mathrm{S}-\mathrm{S}-$ linkages
• B. Hydrogen bonds
• C. Ionic bonds
• D. Peptide bonds

Answer 1

The correct option is D

Peptide bonds

The explanation for Correct Answer

Option (D) Peptide bonds

• The proteins are made up of amino acids.
• The primary structure of proteins refers to the sequence of amino acids which are joined together by forming a bond between the carboxyl groups of one amino acid with the amino group of another amino acid which is a type of covalent linkage.
• The linkage of amino acids by the peptide bond is formed by the condensation reaction(a type of chemical reaction in which two molecules are combined to form a single molecule).

• An example of a protein with a primary structure is haemoglobin.

Option (A) $-\mathrm{S}-\mathrm{S}-$ linkages

• Disulfide linkages are covalent linkages between the Sulfur-containing side chains of cysteine residues.
• These linkages are present in the tertiary structure of a protein.
• Hence incorrect option.

Option (B) Hydrogen bonds

• H-bonds are present in the secondary structure of a protein.
• The secondary structure of protein includes alpha-helix and beta-pleated sheets that are held together by the H-bonds.
• Hence incorrect option.

Option (C) Ionic bonds

• Ionic bonds are present in the tertiary and quaternary structures of the proteins.
• These bonds are known for stabilizing these structures of the protein.
• Hence incorrect option.

Hence, option (D) is the correct answer.