Question

the primary difference between each amino acid is _____.
o the side chain (functional group) of the alpha carbon
o the carboxyl group of the beta carbon
o polar amino acids are able to form inter - protein disulfide bonds, while non - polar amino acids cannot
o polar amino acids contain nitrogen, while non - polar amino acids do not

Explanation:

All amino - acids have a central alpha - carbon bonded to an amino group, a carboxyl group, a hydrogen atom, and a side chain (R - group). The side chain is what varies among different amino - acids, giving them their unique properties. The carboxyl group is common to all amino - acids and is attached to the alpha - carbon, not the beta - carbon. Only cysteine (a sulfur - containing amino - acid) can form disulfide bonds, not all polar amino - acids. Both polar and non - polar amino - acids contain nitrogen in their amino group.

Answer:

the side chain (functional group) of the alpha carbon