The total number of carbon atoms present in tyrosine,an amino acid,is $................$

Assertion $(A)$: The denaturation of proteins can destroy all $1^{\circ}, 2^{\circ}$ and $3^{\circ}$ protein structures.
Reason $(R)$: Curdling of milk is due to denaturation of proteins.
The correct option among the following is

In which of the following is $Keratin$,a fibrous protein,absent?

The proteins which are insoluble in water are

Consider the following statements:
Statement-$I$: The primary structure of a protein represents its amino acid sequence.
Statement-$II$: The $\alpha$-helix and $\beta$-pleated sheet structures of a protein represent its tertiary structure.

Which of the following is the correct structure of $L$-alanine?