Which of the following amino acids has a side chain that carries a negative charge in its conjugate base form?

A. H
B. W
C. C
D. K
E. N

To determine which of the given amino acids has a side chain that carries a negative charge in its conjugate base form, we need to consider the properties of the side chains of each amino acid.

A. H (Histidine) - The side chain of histidine can carry a positive charge at physiological pH (7.4), but it does not carry a negative charge in its conjugate base form. Therefore, option A is not the answer.

B. W (Tryptophan) - Tryptophan does not have a charged side chain. Instead, it has a nonpolar aromatic side chain. Therefore, option B is not the answer.

C. C (Cysteine) - The side chain of cysteine is actually a thiol (-SH) group. In its conjugate base form, the side chain carries a negative charge. This means that cysteine is the amino acid with a side chain that carries a negative charge. Therefore, option C is the answer.

D. K (Lysine) - The side chain of lysine contains an amino group, which can carry a positive charge in its conjugate base form. Therefore, option D is not the answer.

E. N (Asparagine) - The side chain of asparagine is an amide group, which is neutral and does not carry a charge in its conjugate base form. Therefore, option E is not the answer.

In conclusion, the correct answer is C. Cysteine.