kap4 - iced

[ArchivalUser]

Which of the following amino acids would most likely be found on the surface of a protein molecule?


A. Alanine

B. Arginine

C. Isoleucine

D. Leucine

E. Phenylalanine

F. Tryptophan

[ArchivalUser]

B: Arginine is a basic amino acid

[ArchivalUser]

yes..............


The correct answer is B. This question requires two logical steps: first, you need to appreciate that the
hydrophilic amino acids are more likely to appear on the surface of a protein molecule, while hydrophobic
amino acids are most likely be found in its interior. Next, you need to figure out which of the amino acids listed is
hydrophilic. If you recall that arginine is a basic amino acid that is positively charged at physiologic pH, you
should be able to answer this question right away.

All of the other choices have neutral side chains and are uncharged at physiologic pH. They would most likely
be found in the hydrophobic core of the protein structure. Alanine (choice A), isoleucine (choice C), and leucine
(choice D) all have aliphatic side chains; phenylalanine (choice E) and tryptophan (choice F) have aromatic
side chains.