Question

G what is the difference between the sidechains of leucine and isoleucine? select one:

a. one is charged, the other is not
b. one has more h-bond acceptors than the other
c. isoleucine has a carbon 'branched' closer to the alpha carbon than does leucine
d. they have different numbers of carbons

Answer 1

c. Isoleucine has a carbon “branched” closer to the alpha carbon than does leucine.

The structure of leucine is CH3CH(CH3)CH2CH(NH2)COOH.

The structure of isoleucine is CH3CH2CH(CH3)CH(NH2)COOH.

In leucine, the CH3 group is two carbons away from the α carbon; in isoleucine, the CH3 group is on the carbon next to the α carbon.

Thus, isoleucine has the closer branched carbon.

“One is charged, the other is not” is incorrect. Both compounds are uncharged.

“One has more H-bond acceptors than the other” is incorrect. Each acid has two H-bond acceptors — the N in the amino and the O in the carbonyl group.

“They have different numbers of carbon atoms” is incorrect. They each contain six carbon atoms.