Final answer:
The C-terminal residue of the peptide AYSDG is glycine, which is the last amino acid in the sequence. The hydroxyl group on certain amino acids allows for phosphorylation. The correct option is A.
Step-by-step explanation:
The C-terminal residue of the peptide AYSDG is glycine. Peptides are written from N-terminus (amino end) to C-terminus (carboxyl end), so the last amino acid in the sequence given, AYSDG, is at the C-terminus. Therefore, the correct answer is a) Glycine.
The property that enables the amino acid residues serine, threonine, and tyrosine to be phosphorylated is that they contain a hydroxyl group (c).