Protein Classification and Structure

Study Notes

Proteins are complex organic compounds of C, H, O, N, S, and P.
The name protein originated from the Greek word "proteios," meaning "first or primary in importance."

Simple proteins yield only amino acids or their derivatives upon hydrolysis.
Conjugated proteins are composed of a simple protein combined with a non-protein substance (prosthetic group).
Derived proteins are produced from the breakdown of natural proteins by heat, enzymes, or chemicals.

Include collagen, elastin, keratin, myosin, and fibrin.
Collagen forms about 50% of animal tissues and is the major protein in connective tissue.
Elastin is found in elastic tissues and is easily digested by proteolytic enzymes.
Keratin is found in feathers, wool, hooves, and nails.
Myosin is a protein found in muscle.
Fibrin is a blood clotting protein formed from fibrinogen.

Nucleoproteins combine with nucleic acids as the prosthetic group.
Glycoproteins contain about 4% firmly bound hexosamine.
Mucoproteins combine with mucopolysaccharides like hyaluronic acid.
Lipoproteins combine with lipids like lecithins, cephalins, cholesterol, and fatty acids.
Chromoproteins are conjugated with pigments.
Phosphoproteins are linked to phosphoric acid through serine.
Metalloproteins are conjugated with metals such as Fe, Co, Cu, Mn, and Zn.

Vital for every living cell.
Act as enzymes, hormones, and structural components of cell protoplasm and membranes.
Involved in oxygen and nutrient transport, muscle contraction, acid-base balance, osmotic pressure regulation, immunity, blood clotting, and heredity.
Major component of blood, muscles, and connective tissues in animals.
Excess protein is broken down and used for energy.