Types of Proteins

Proteins can be classified by cellular function.

Type	Function	Example
structural	provides mechanical support to large animals & provides them with outer coverings ----------------------------------------------------------------------------------------------- builds tendons & cartilage forms hair, skin, wool & nails	collagen keratin
movement contractile	contracts muscles ----------------------------------------------------------------------------------------------- sperm & bacterial mobility occurs by means of long flagella	myosin actin
transport	transports oxygen transports lipids (transports iron from liver to bone marrow) ----------------------------------------------------------------------------------------------- entry into a cell is facilitated by binding of a molecule to a receptor at the cell surface the receptor helps the food molecule to cross the cell membrane & enter the cytoplasm, where it is utilized to provide energy for cellular functions	hemoglobin lipoprotein
storage	stores iron in liver for production of red blood cells	casein ferritin
nerve impulse transmission	involved in vision impulse transmission in nerve cells	rhodopsin acetylcholine
regulation hormone	regulates many aspects of cell function ----------------------------------------------------------------------------------------------- increases glucose metabolism regulates body growth ----------------------------------------------------------------------------------------------- Organisms can only function within a limited set of conditions for example, body temperature, pH of blood, blood glucose levels Hormones help regulate these conditions. ----------------------------------------------------------------------------------------------- Many hormones are proteins. However, some are lipids. For example testosterone, estrone(estrogen), and progesterone are lipids not proteins	insulin human growth hormone
catalysis enzyme	All biochemical catalysts known as enzymes are proteins. They catalyze almost all of the chemical reactions that occur in a living cell. Reactions that would take days or weeks without enzymes take seconds. ----------------------------------------------------------------------------------------------- catalyzes hydrolysis of sucrose catalyzes hydrolysis of protein	sucrase trypsin
antibody	antibodies are specific protein molecules produced by specialized cells of the immune system in response to foreign bodies (antigens) ----------------------------------------------------------------------------------------------- antigen - is a foreign invader such as bacteria or virus ----------------------------------------------------------------------------------------------- antibodies recognizes and destroys bacterial or viral antigens	immunoglobulins