ABSTRACT
Antibodies are involved in protection of organisms against various types of foreign materials, which in some cases are also proteins. Proteins of the human skin, fingernails, hair, and the protein coats of viruses perform protective functions. The number of different proteins in nature is tremendous since the proteins from one species are different from those of another species. The nature of hydrophobic bonds may best be understood as an attempt of water to maintain its integrity. Many enzymes and other proteins are composed of a single polypeptide chain. A large number of enzymes are composed of more than one polypeptide chain. One type of polypeptide binds substrate and catalyzes the reaction of carbamyl phosphate and l-aspartate to form carbamylaspartate, while a second type of polypeptide is inactive as an enzyme but binds the allosteric inhibitor cytidine triphosphate. Enzymes are usually either membrane bound or fully soluble.
