Which of the following statement(s) is/are true concerning the cell plasma membrane?

a.The plasma membrane is composed of amphipathic molecules

b.The hydrophobic core of the lipid bilayer of the cell membrane contains specialized transport proteins which maintain the intracellular ionic milieu different from the extracellular fluid

d.The membrane proteins of nerve cells are highly voltage-dependent

The plasma membrane defines the boundary of the cell and serves to contain and concentrate enzymes and other macromolecule constituents. The plasma membrane is composed of amphipathic molecules, mainly phospholipids and proteins that contain distinct regions that are either insoluble in water (hydrophobic) or soluble in water (hydrophilic). The plasma membrane forms a continuous barrier between the aqueous extracellular and intracellular fluids. Transport proteins in the membrane act as regulated channels or transporters to maintain the intracellular ionic milieu that is clearly different from the extracellular milieu. In some cells, membrane proteins are diversified such as in nerve cells where the ion channels are highly voltage-dependent, providing the basis for information transmission in the form of electrical impulses. Most plasma membrane proteins extend externally and bear carbohydrate moieties primarily as oligosaccharide chains that contribute to the cell coat or glycocalyx.