Campbell 3rd ed. Pages 68 to 78 Proteins have numerous important roles in the living organism.
Proteins form many structural features such as hair, hooves, and tendons.
The elements in proteins are carbon, hydrogen, oxygen, nitrogen, and, in some proteins, sulfur. All proteins are polymers of amino acids covalently bonded in long chains that subsequently coil and fold into complex shapes that determine the function of the resulting protein molecule. The chemical bond that holds amino acids together is called a peptide bond. The bond forms between the functional groups of two amino acids. Many amino acids linked together form a polypeptide.