Which amino acid is small enough to fit into the tight corners of a protein molecule?

Question

Quizplus · Accepted Answer

Glycine is the only amino acid that has a hydrogen atom as its R group, making it the smallest amino acid. Thus, it can fit into tight corners of a protein molecule. Proline has a bulky R group that can disrupt protein folding, while cysteine, asparagine, and glutamine have larger R groups that cannot fit into tight spaces as easily as glycine.

Which Amino Acid Is Small Enough to Fit into the Tight