The difference between polar and nonpolar amino acid groups.

How do you tell the difference between the non-polar R group and the polar but neutral R group?

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...nt ones in this case.

You should be able to identify which type of chemistry applies to each side chain and hence decide whether they are polar. I have explained this below for each amino acid, subdivided into groups based on further side chain chemistry. You may also find it helpful to understand these classifications, as they have functional significance.

1. Aliphatic amino acids: G, A, V, L, I, P: NONPOLAR
All of these have simple hydrocarbon-only chains which are non-polar and unable to participate in hydrogen bonding. Proline looks different due to the ring structure but is still a hydrocarbon (count the atoms).

2. Sulfur side chains:
M: Nonpolar
C: Weakly polar (but often forms disulfide bonds anyway)
The S atom in methionine is surrounded by hydrocarbon chains on both sides and is unable to attract charge from the neighboring hydrogens. It is hence ...