Question

In haemoglobin, which of the following amino acids acts as a blood buffer?
A.Histidine
B.Glutamine
C.Aspartic acid
D.Lysine

Answer 1

Hint: Amino acids are organic compounds that combine to make proteins. Amino acids and proteins are the building blocks of proteins, they join together with peptide bonds and make large polypeptide chains. An amino alkanoic acid can act as a buffer because it can react with added acids and bases to stay the pH nearly constant.

Complete step by step answer:
Because an amino alkanoic acid has both an acidic group (COOH) and a basic group $(NH_2)$, it can act as both an acid and a base. In very acidic media, the $NH_2$ group is within the protonated form, and in very basic media, the COOH group is within the deprotonated form. A mix of a weak acid and its conjugate base is what we know as a buffer. Haemoglobin is equivalently almost about 6 times more crucial as compared to the plasma proteins because their concentration is about two times more and it contains about 3 times the amount of histidine residues per molecule.

So, the right answer is option A. Histidine.

Note:
 It is important to note that at an intermediate pH (the isoelectric point), both ends are in their ionic form. In both regions, we will add small amounts of acid or base, and therefore the pH won't change much. Thus, an amino alkanoic acid has two regions during which it can act as a buffer.