The protein that is a structural material is

An electric current is passed through an aqueous solution of a mixture of alanine (isoelectric point $6.0$), glutamic acid $(3.2)$, and arginine $(10.7)$ buffered at $pH$ $6.0$. What is the fate of the three amino acids?

Which of the following is not an amino acid?

Which of the following compounds is an amino acid?

Identify the basic $\alpha$-amino acid from the following.

The main structural linkage of protein is