Biological functions of proteins

Proteins play an important role in the functions of human body. Proteins are naturally occurring polypeptides of molecular weight greater than 5000. These large molecules perform a wide range of biological functions. Enzymes which are proteins are capable of boosting rates of reactions up to 10¹² times.  Some carrier proteins are capable of transporting tiny molecules and ions in the blood and within cells. Hemoglobin and ferritin are examples of such proteins. Some proteins impart tensile strength to skin, bone and teeth. Such proteins are called mechanical proteins and collagen is an example. Actin and myosin are two proteins which help in muscle contraction in human body. Myosin is also capable of converting chemical energy to mechanical energy. The antibodies which protect human body by destructing foreign cells are proteins. Rhodopsin is a visual protein which is located in membranes of retinal cells is capable of transferring signals to the interior of the cell.