Final answer:
The part of each amino acid that varies from others is the side group or R-group, which gives each amino acid its unique properties and influences protein structure and function. (Option b)
Step-by-step explanation:
The part of each amino acid that is different from the others is the side group or R-group. All amino acids have a similar structure consisting of an amino group (NHâ‚‚), a carboxyl group (COOH), and a unique side chain attached to the alpha (a) carbon. It's this R-group that varies among different amino acids, providing them with distinct characteristics such as size, shape, solubility, and charge.
These side chains can be nonpolar, polar but uncharged, negatively charged, or positively charged, and they play a crucial role in the structure and function of proteins. For instance, the R-groups of cysteine and methionine contain sulfur, which influences how proteins containing these amino acids fold and function.