How many different tripeptides can exist,each containing one residue of glycine,one of l-threonine,and one of l-arginine?

Question

Quizplus · Accepted Answer

There are 2 ways to choose the position of glycine, then 1 way to choose the position of threonine, and only 1 way to choose the position of arginine since the other two positions are already occupied. Therefore, there are 2x1x1 = 2 ways to arrange the three residues. However, since glycine and arginine are both chiral and can exist in two different stereoisomers, there are a total of 2x2 = 4 different possible tripeptides. However, since the question specifies l-threonine and l-arginine, only half of these 4 tripeptides are relevant, giving a total of 4/2 = 2 possible tripeptides.

Therefore, the best choice is C.

How Many Different Tripeptides Can Exist,each Containing One Residue of Glycine,one