Final answer:
The R group -CH₃ (methyl group) is associated with nonpolar amino acids like alanine. It makes the amino acid hydrophobic and is an example of an R group that does not interact well with water. -OH is a polar functional group and not a part of a nonpolar amino acid's R group.
Step-by-step explanation:
The question focuses on identifying what kind of R group is associated with a nonpolar amino acid. The R group is the side chain attached to the α-carbon of an amino acid which gives it its unique properties. Nonpolar amino acids typically have hydrophobic side chains that do not interact well with water.
In our case, -CH₃ (methyl group) would be found in the R group of nonpolar amino acids such as alanine. These side chains do not form bonds with water molecules, thereby exhibiting nonpolar behavior. On the contrary, an -OH (hydroxyl group) is a functional group found in polar amino acids, not nonpolar ones, as it can form hydrogen bonds with water, making the amino acid more hydrophilic. Some examples of nonpolar amino acids with an aliphatic R group are glycine (Gly), valine (Val), leucine (Leu), and isoleucine (Ile), which all contain chains of carbon atoms and are known for their hydrophobic nature.