Suppose that a glutamine residue in the active site of an enzyme was mutated to alanine. as expected, the alanine mutant was inactive, suggesting that the glutamine residue was critical to the catalytic mechanism. which mutation is most likely to restore wild-type level of activity to the alanine mutant?

a to m

a to n

a to f

a to k

a to e

A to N

Explanation:

Glutamine is an amino acid with a polar, uncharged side chain. The mutation to alanine, an amino acid with a non-polar side chain, completely affects the enzymatic activity. This makes sense considering the difference in the nature of both amino acids.

To restore the wild-type level of activity the alanine would have to mutate to another polar uncharged amino acid. Among the given options, only Asparagine (N) has a similar chemistry to Glutamine.

Solution :

The flow of oxygen in the blood is been transported by two ways :

1. in plasma 1.5%

2. bound to hemoglobin 98.5%

As the oxygen loads in the body, affinity of the Hb makes the oxygen loading very efficient in the blood. The Hb molecule gets saturated when all the 4 hemes are oxygen binded.

The decreased pH weakens the hemoglobin oxygen binding in the tissues.

Higher temperatures in the oxygen means a lower affinity and thus more oxygen is released and so the oxygen unloads.

Increase in the temperature, the BPG and the modification of the structure in the hemoglobin decreases the affinity for the oxygen and further enhances the unloading of the oxygen in the blood.