How many subunits are present in hemoglobin?

Which of the following is not an amino acid?

Which structure of protein remains intact after coagulation of egg white on boiling?

Assertion: $\alpha$-amino acids exist as internal salt in solution as they have amino and carboxylic acid groups in near vicinity.
Reason: $H^{+}$ ion given by carboxylic group $(-COOH)$ is captured by amino group $(-NH_2)$ having lone pair of electrons.

Which of the following amino acids does $NOT$ contain a chiral carbon?

Match List-$I$ with List-$II$

List-$I$ Natural Amino acid	List-$II$ One Letter Code
$A$. Arginine	$I$. $D$
$B$. Aspartic acid	$II$. $N$
$C$. Asparagine	$III$. $A$
$D$. Alanine	$IV$. $R$

Choose the correct answer from the options given below :-