The dipeptide given below is used as:

$A$ tetrapeptide has a $-COOH$ group on alanine. This produces glycine $(Gly)$,valine $(Val)$,phenylalanine $(Phe)$,and alanine $(Ala)$ on complete hydrolysis. For this tetrapeptide,the number of possible sequences (primary structures) with the $-NH_2$ group attached to a chiral center is:

Given below are two statements $:$
Statement $(I):$ On hydrolysis,oligopeptides give rise to a fewer number of $\alpha$-amino acids,while proteins give rise to a large number of $\beta$-amino acids.
Statement $(II):$ Natural proteins are denatured by acids,which convert the water-soluble form of fibrous proteins to their water-insoluble form.
In the light of the above statements,choose the most appropriate answer from the options given below $:$

Which type of linkage is present in the structure of proteins?

Which of the following amino acids contains a heterocyclic ring in its side chain $(R)$ group?

Peptides are: