Major roles of proteins – the first use of proteins is in the cell membrane where they are channel or carrier proteins and they help with facilitated diffusion and active transport.
The second and most widely recognized role of proteins in living structures is enzymes. They act as organic catalysts and catalyze many biochemical reactions in the body and in the world around us.
Proteins can also act as transporters and are commonly found as globular proteins. Hemoglobin is an example of transport protein; it carries oxygen from the lungs to the tissue whilst myoglobin performs a similar function by taking oxygen from the hemoglobin and storing it or carrying it around until the muscles need it.
Another use of protein is in the immune system of the human body, these are called immuno – proteins. They are blood proteins whose activities affect or play role in the immune system. Some soluble proteins bind with antigen to induce or affect antigen specific functions in immuno regulation and or hypersensitivity, these then attack microbes to get rid of infections etc.
Structural proteins are of a fibrous nature, and the most familiar of the fibrous proteins are the keratins. They form the protective coating of all land vertebrates. Examples: Skin, fur, hair, wool, claws, nails, hooves, horns, scales, beaks and feathers.
Contractile proteins are proteins which allow contraction in muscles and therefore aid in movement. Actin and myosin form sarcomeres, which are the basic units of contraction.