a. Functions of the lipid of the cell membrane:
i. The lipid layer in the middle of the membrane is impermeable to the usual water-soluble substances such as ions, glucose. and urea. sat-soluble substances, such as oxygen, carbon dioxide, alcohol, can penetrate this portion of the membrane with ease,
ii. The cholesterol in the cell membrane mainly help to determine the degree of permeability of the bilayer to water-soluble constituents of the body fluids. The cholesterol also controls much of the fluidity of the membrane as well.
b. Functions of the cell membrane proteins
i.Adhesion molecule : Some are cell adhesion cell adhesion molecules that anchors cells to their neighbors or to basal lamina.
ii. Pumps There arc proteins that function as pumps, actively transporting ions across the membrane.
iii. Carriers : Some proteins function as carriers, transporting substances down electrochemical gradient by facilitated diffusion.
iv. Ions channels Still others are ens channel which, when activated, permit the passage of ions into or out of the cell.
v. Receptors Proteins in another group function as receptors that hind neurotransmitters and hormones, initiating physiological changes inside the cell.
vi. Enzymes Proteins also function as enzymes, catalyzing reactions at the surfaces of the membrane,
vii, Antibody processing and distinguishing self from nonself
i. Many of them are electrically negatively charged, which gives most cells an over all negatively surface charge that repels other negative objects.
ii. The glycocalyx of some cells attaches to the glycocalyx of other cells, thus attaching cell one to another.
iii. Many of the carbohydrates act as receptor substances for binding hormones such as insulin, and when bound, this combination activates attached internal proteins that in turn activate a cascade of intercellular enzymes.
iv. Some carbohydrate moieties enter into immune reactions.
Q. List the functions of the cell membrane.