1. C ELL M EMBRANE

2. Function: controls the passage of materials into and out of a cell. Location: surrounds the cell; inside of the cell wall if one is present.

3. F LUID M OSAIC MODEL Cells are surrounded by fluids, inside the cell itself and around it. The membrane is flexible not rigid or solid Have a mixed composition “mosaic” of diverse and colorful phospholipids, proteins, sterols, and carbohydrates incorporated within.

4. S TRUCTURE : consists of a double layer of phospholipids. Phospholipid-a molecule composed of three basic parts: a charged phosphate group, glycerol, and two fatty acid chains.

5. - Polar -Hydrophilic (Water-loving) -Nonpolar -Hydrophobic (Water-fearing) PO 4 - Phospholipid - Phosphorus Head Fatty Acid Chain

6. - Head- -Tail- -Head- Sandwich concept (Bread) = Head (Meat) = Tails (Bread) = Head - The tails point toward each other in the center of the membrane -The heads point to the fluid cytoplasm and the fluid outside of the cell.

7. The hydrophilic head of a phospholipid is polar and composed of glycerol and a phosphate group. The two hydrophobic tails are nonpolar and are composed of two fatty acids. Because of the properties of polar heads and nonpolar tails, the phospholipids arrange themselves in layers.

8. There are other molecules embedded within the phospholipid layers. These molecules have several functions:  Cholesterol molecules strengthen the cell membrane.  Some proteins help materials cross the membrane.  Carbohydrates serve as identification tags. All of these components are working together for the membrane to function properly.