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

Step 1: Classify the amino acids by side chain. Acidic residues carry a free carboxyl group, and those are glutamate and aspartate; basic residues are lysine, arginine and histidine; the rest are neutral.

Step 2: The question states the fibrinopeptides are acidic, so the residues responsible must be the carboxyl-bearing pair, glutamate and aspartate. That is the answer.

Step 3: Functionally these negatively charged fibrinopeptides sit at the N-termini of the fibrinogen $\alpha$ and $\beta$ chains and are clipped off by thrombin, allowing fibrin monomers to assemble into a clot.

Step 4: Rule out the rest on charge alone: serine and threonine are neutral hydroxyl types, histidine and lysine are basic, and glutamine and valine are neutral, so only glutamate and aspartate make a peptide acidic.

\[\boxed{\text{Glutamate and aspartate}}\]