Which protein is responsible for pigmentation in the animal body?

Statement $- I :$ All amino acids are protein-forming amino acids.
Statement $- II : R-$ group is a variable group in an amino acid.

Which of the following amino acids are non-polar? $(1)$ Arginine $(2)$ Leucine $(3)$ Proline $(4)$ Serine $(5)$ Lysine $(6)$ Methionine $(7)$ Glycine $(8)$ Valine $(9)$ Threonine

In the structure of a protein,which groups are responsible for the $N$-terminal and $C$-terminal,respectively?

When catabolism of proteins exceeds synthesis of proteins,then:

Which one is the most abundant protein in the animal world?