Question

Fibrinopeptide A and fibrinopeptide B are acidic due to the presence of which amino acids in its structure -

• A. Serine and threonine
• B. Glutamate and aspartate
• C. Histidine and lysine
• D. Glutamine and valine

Answer 1

The Correct Option is B

Fibrinopeptides are known for their acidic properties due to the presence of certain amino acids. Amino acids that contribute to acidity in proteins typically contain carboxyl groups (-COOH) in their side chains, allowing them to donate protons (H⁺) and thus function as acids. Glutamate (or glutamic acid) and aspartate (or aspartic acid) are two such amino acids. Both contain acidic side chains due to their carboxyl groups, making them capable of ionization in physiological pH, which contributes to the overall acidic nature of the fibrinopeptides.

Let's examine why the other options do not fit:

• Serine and threonine: These amino acids contain hydroxyl groups (-OH) in their side chains, which do not contribute to acidity.
• Histidine and lysine: Although these are basic rather than acidic; histidine contains an imidazole group and lysine an amino group, both capable of accepting protons.
• Glutamine and valine: Glutamine is a derivative of glutamate but lacks the acidic carboxyl group, and valine has a non-polar aliphatic side chain, neither contributing to acidity.

Therefore, the presence of glutamate and aspartate in fibrinopeptide A and B is the reason these peptides are considered acidic.