Q: All individual amino acids are soluble in water; however, not all peptides are soluble. Which of the following choices best explains this?
A		The R groups of the amino acid residues in the peptide are charged at physiological pHs
B		The R groups on all amino acids can interact noncovalently with water at pH = 7.4 (the pH of a normal, healthy body)
C		All peptides are insoluble in water
D		Individual amino acids are zwitterions at physiological pHs

Protein Structure and Function | Acid/Base Equilibria |