Plasma Membrane: Outer surface that regulates entrance and exit of molecules. It's considered a phospholipid bilayer that is said to be selectively permeable because it allows certian molecules, but not others, to enter the cell. Phospholipid bilayer molecules has a polar head which, are attracted to water, they postion themselves to face toward the watery environment outside and inside the cell. Nonpolar tails also involved with phospholipids bilayer, they are not attracted to water,they turn inward one another where there is no water. Plasma membrane it's function is to contain, protect and provide unit structure. The surfaces of plasma membrane are generally studded with proteins that perform different functions like the reception of nutrient or the anchoring of the flagellum. The plasma membrane structure is referred to as fluid masaic because it is a two dementional fluid (like a soap bubble) of freely diffusing lipids that is dotted with proteins.
