Because the PK_a is near 7, ____ Side-Chains are Often

Question

Because the pKais near 7, ____ side-chains are often involved in general acid-base catalysis.
A) cysteine
B) aspartate
C) glutamate
D) lysine
E) histidine

Accepted Answer

The pK_a, also known as the pKa, is the pH at which half of the ionizable groups are protonated and half are deprotonated. It is close to 7, so it indicates that the amino acid side chain with a pKa close to 7 is likely to be involved in general acid-base catalysis. Histidine has a side chain pKa of approximately 6, making it a good candidate for this role. Therefore, choice E, histidine, is the best answer.

Because the pKa is near 7, ____ side-chains are often involved in general acid-base catalysis.

Because the pK_a is near 7, ____ side-chains are often involved in general acid-base catalysis.