(c) draw the structure of any two aminoacids which bears a heterocyclic unit as all or part of the r side chain of the aminoacid, and highlight and name the particular heterocyclic unit present in the aminoacid.

Here I show you  tryptophan and  tyrosine

Explanation:

of the 21 amino acids, there is five amino acid that have a heterocyclic group as part of the R side chain: Histidine, proline, Phenylalanine, tyrosine, and tryptophan. Each one has a unique nature and the heterocyclic group, mainly in tyrosine, and tryptophan allows to absorb the UV light (280 nm)