Denaturation of proteins leads to the loss of their biological activity due to:

Identify the $N$-terminal and $C$-terminal $\alpha$-amino acids respectively in the following polypeptide fragment: $Ala-Gly-Ser-Tyr-Gly$.

Identify the basic amino acid from the following:

What is the total number of essential amino acids?

When urea is heated,it forms biuret,the alkaline solution of which forms $.....$ with $CuSO_4$ solution.

Treatment of compound $O$ ($1,2-$diethylbenzene) with $KMnO_4 / H^{+}$ gives $P$ (phthalic acid),which on heating with ammonia gives $Q$ (phthalamide). The compound $Q$ on treatment with $Br_2 / NaOH$ produces $R$ ($o-$phenylenediamine). On strong heating,$Q$ gives $S$ (phthalimide),which on further treatment with ethyl $2-$bromopropanoate in the presence of $KOH$ followed by acidification,gives a compound $T$.
$(1)$ The compound $R$ is
$(2)$ The compound $T$ is
$(A)$ glycine
$(B)$ alanine
$(C)$ valine
$(D)$ serine
Identify the correct options for $(1)$ and $(2)$.