Fluid Mosaic Model of the Cell Membrane

3 Main Functions of the Cell Membrane 1. Flex - but still maintain shape 2. Regulate the exchange of materials between the cell’s contents and the external environment (homeostasis)  selectively permeable 3. Communicate with other cells

Basic Structure of the Cell Membrane: “Phospholipid bilayer with embedded proteins”

Phospholipid Bilayer (#1) Two layers: 1. Phosphate head (#1a) On the outside Polar Attracts water hydrophillic

2. Lipid Tails (#1b) Inner layer Fatty acids Non-polar Repel water Hydrophobic Moveable (unsaturated lipids) Not as fluid: more saturated lipids

Embedded Proteins (Three types)

A. Transport Protein (#2) Regulate movement of molecules through membrane May have channels to move substances through

B. Recognition Proteins (#3) Serve as attachment sites for ID markers

C. Receptor Protein ( #4) Binding sites for attachment of molecules Activate a cell response

Carbohydrate Antennae (#5) ID marker Tell what type of cell Tell whose cell

Cholesterol Molecules (#6) Holds two layers together; provides structure More cholesterol Stronger Less fluid