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.
Proteins are polypeptides.
Enzymes Campbell 3rd ed. Pages 91-97 Enzymes are a particularly important class of proteins. They control the many chemical reactions that keep the cell alive. Enzymes do this by acting as catalysts in biochemical reactions. Acting as catalysts the enzyme cause chemical reactions that would not occure in the absence of the enzymes or speed up reactions that would be very slow.