There are 20 different amino acids. What makes one amino acid different from another?
A) different carboxyl groups attached to an alpha (α) carbon
B) different amino groups attached to an alpha (α) carbon
C) different side chains (R groups) attached to an alpha (α) carbon
D) different alpha (α) carbons
E) different asymmetric carbons
Answer: C) different side chains (R groups) attached to an alpha (α) carbon