Ans.
Hemoglobin, amylase, immunoglobulin, collagen, and aquaporin are molecules that belong to a common class of biomolecules, known as proteins. Proteins are made up of polypeptide chains, in which amino acids are connected together with the help of peptide bonds.
Hemoglobin and immunoglobulins are made up of four polypeptide chains, collagen is are made up of three polypeptide chains, while amylase and aquaporin are made up of single polypeptide chain.
Thus, the correct answer is 'option c). proteins.'
