Final answer:
Aspartic acid and cysteine are the amino acids among the options provided that will undergo a chemical change in their R-group as a function of pH due to their ionizable side chains.
Step-by-step explanation:
Among the amino acids listed, aspartic acid and cysteine will undergo a chemical change in their R-group as a function of pH. Aspartic acid has an acidic side chain that will donate a proton and become negatively charged at a higher pH. Similarly, cysteine contains a thiol (sulfhydryl, -SH) group in its side chain, which can ionize to form a thiolate anion (-S-) at higher pH values.
Proline, on the other hand, has a secondary amine as part of its R-group structure in a ring formation, which is less reactive to changes in pH. Alanine has a methyl group as its R-group, which is nonpolar and will not ionize under normal physiological pH changes.
Thus, the correct answers are b. aspartic acid and d. cysteine.