Histidine is the most impoant amino acid for buffering in normal conditions because
Correct Answer: PKa value is closer to pH
Description: Ans. is 'c' i.e., PKa value is closer to pH Maximal buffering capacity occurs at pH equal to pka of buffer.Therefore, to work as a best buffer at physiological pH amino acid should have pka value close to physiological pH (7.4).Amino acids can have buffering action due to three ionizable groups :a-carboxyl group :- Different amino acids have pka value of a-carboxyl group between 3.5-4. So, carboxyl group of amino acids has maximum buffering capacity between pH 3.5-4.a-amino group :- Different amino acids have pka value of a-amino group between 8.0-9.0. Thus, a-amino group has maximum buffering capacity between pH 8.0-9.0.Special ionizable group (in some amino acids):- Among special ionizable group of amino acids, imidazole group of histidine has pka value 6.5-7.4, which is closest to physiological pH. Hence, histidine (due to imidazole group) has maximum buffering capacity at physiologial pH.
Category:
Biochemistry
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