Proteins are $.......$.

Among the following,the achiral amino acid is

The total number of negative charges in the tetrapeptide,$Gly-Glu-Asp-Tyr$,at $pH$ $12.5$ will be $......$ .

Which of the following is not an essential amino acid?

When dilute $H_2SO_4$ is added to an alkaline solution of protein,a violet color is obtained. What is this test called?

Assertion $(A)$: In aqueous solution,$\alpha$-amino acids exist as an internal salt called a zwitter ion.
Reason $(R)$: Proline is a natural amino acid having a secondary amino group. The correct option among the following is: