Question

Which is the BEST description of hemoglobin A1c

A. 2,3-diphosphoglycerate bound to hemoglobin at the time of production

B. glucose covalently bound to hemoglobin at the time of production

C. the glycosylated product of insulin's action on glucose

D. two alpha chains and two delta chains comprising the glucose molecule

Answer 1

Option B is the correct answer.

HbA1c is a hemoglobin compound produced when glucose reacts non enzymatically with the amino group on a hemoglobin molecule forming a ketoamine. The glucose molecule is attached to N-terminal valine of the β-polypeptide chains of haemoglobin. HbA1c formation is directly proportional to blood glucose level.The normal range of HbA1c in blood is between 4% and 5.6%.

Option A is incorrect because it is glucose which is attached to haemoglobin,not 2,3 diphosphoglycerate.

Option C is incorrect because glycation and glycosylation are different.First one is non enzymatic addition of sugar and second one is enzymatic addition of sugar.HbA1c is formed not due to insulin action on glucose.But HbA1c test can be used for the diagnosis of diabetis mellitus.

option D is also incorrect.Adult Hb is made up of two alpha and two beta sub units,It is a tetramer.