Proteins: Characteristics, Examples and Structure

A. Proteins are organic molecules which contain C, H, O, N and often S (sulfur) B. Examples of Proteins: 1. Catalytic Proteins: Almost all known ENZYMES are composed of proteins. 2. Structural Proteins: i Proteins are components of all cell membranes ii Keratin= protein in fingernails, animal horns, and feathers iii Collagen- protein in cartilage, tendons, and bones 3. Transport Proteins: Some proteins act as transport molecules, e.g. hemoglobin in vertebrate red blood cells transports O2 to cells 4. Hormonal Proteins: Some proteins act as hormones, e.g. insulin , secreted by the pancreas, regulates blood sugar (glucose) levels 5. Storage proteins: Ex. ovalbumin (the protein in egg white) is used by the developing chick embryo 6. Antibodies: protein compounds which combat bacteria, viruses, and other foreign substances in an organism