The Plasma Membrane (Cell Membrane) The Fluid Mosaic Model

Introduction WATCH THIS!!!

Functions 1.Separates the cell’s interior environment from the external environment. 2.Regulates what enters and exits the cell. 3.Communicates with other cells.

Selectively Permeable Based on size and solubility of molecule as well as specific protein channels.

Cell Membrane Structure Phospholipid bilayer Proteins Glycoproteins (protein + carbohydrate) Cholesterol molecules Isolation function Regulation and Communication Functions

The Phospholipid Bilayer Phospholipids arranged as a continuous double layer.

The Fluid Mosaic Model Fluidity of Membrane Phospholipids and proteins move laterally. Components are not static. Mosaic-like Composed of many different macromolecules. WATCH THIS!!!

The Fluid Mosaic Model

Components Phospholipids –Bilayer acts as a barrier. –Hydrophobic nature causes membrane to be impermeable to water- soluble molecules. –Phospholipids are not bonded to one another, so this double layer is quite FLUID with the individual molecules moving about easily.

Components Cholesterol –Structural support – prevents fatty acids from tangling –Regulates fluidity of membrane. High temps: makes outer membrane less fluid. Low temps: prevents the membrane from freezing and maintains membrane fluidity.

Components Membrane Protein Classification 1.Integral Embedded (integrated) in the phospholipid bilayer –Recognition proteins (special binding sites) –Receptor proteins (receives signals) –Transport proteins (channel or gated) Can be attached to other proteins 2.Peripheral (smaller) Bound to Integral Proteins or embedded in membrane (one side only), attached to cytoskeleton Structural support

Components Membrane Proteins WATCH THIS!!!

Components Glycoproteins –Carbohydrate chains attached to membrane proteins. –On outer surface only.

Components Glycolipids –Carbohydrate chains attached to the phospholipids. –On outer surface only.