What is the smallest functional and structural unit of protein?
The smallest structural unit of a protein is the amino acid. The
smallest functional unit of a protein is a little ambiguous,
because some might consider the amino acid to be functional (after
all, some can function as neurotransmitters). Or, some might
consider the peptide (di, tri, etc) to be a functional unit. One
could argue what exactly is the smallest functional unit of a
protein.