An enzyme is in the class of organic compounds or molecules known as proteins or polypeptides. Enzymes play a role in reactions at the cellular level.
In addition to serving as enzymes, proteins play roles in the immune system and are components in the cell membrane. Proteins are formed by linking together monomers of amino acids via peptide bonds. Most organisms use 21 major amino acids to construct proteins. Other organic molecules include carbohydrates, lipids and nucleic acids.
Organic compounds are compounds that are found in living organisms and contain more than one type of element. They contain carbon-hydrogen bonds, which distinguish them from inorganic compounds.