The exoskeleton of birds and mammals is composed of which biomolecule?

Identify the $X$ figure.

$A$ nanopeptide contains .... peptide linkages.

Proteins have a primary structure. If you are given a method to know which amino acid is at either of the two termini (ends) of a protein,can you connect this information to the purity or homogeneity of a protein?

What is the $R$ group present in glycine?

What is the quaternary structure of a protein?