Structures of alanine at $pH = 2$ and $pH = 10$ are respectively

Which of the statements about "Denaturation" given below are correct?
$1.$ Denaturation of proteins causes loss of secondary and tertiary structures of the protein.
$2.$ Denaturation leads to the conversion of double strand of $DNA$ into single strand.
$3.$ Denaturation affects primary structure which gets distorted.

Which one of the nitrogen atoms of histidine is protonated first?

Define the following terms related to proteins: $(i)$ Peptide linkage,$(ii)$ Primary structure,$(iii)$ Denaturation.

$HC\equiv CH$ $\xrightarrow[HgSO_4]{H_2SO_4} (A)$ $\xrightarrow[(1) NH_3 + HCN]{(2) H_3O^{\oplus}} (B);$ The product $(B)$ of the given reaction is:

Which of the following tests is not used for testing proteins?