Question

What is the function of the “R group” in a protein?

Answer 1

"The –R group, also called a lateral chain, is the variable part of the amino acid molecule. The –R group can be a complex carbonic chain, a substituting methyl group (forming then the amino acid alanine) or even only a hydrogen (forming glycine, the simplest amino acid). So the –R group is important because it is the differentiation factor of amino acids."

Answer 2

Not my work but it sure does explain it better than I