The Fluid Mosaic Model of the Cell Membrane

Getting Materials In and Out of Cells

The Phospholipid Bilayer is Semi Permeable

Some molecules can diffuse freely through membranes, while others require assistance from membrane proteins (facilitated diffusion). These two methods allow materials to flow along their concentration gradient. Since NO energy is required, this is called passive transport. Some molecules must enter the cell against their concentration gradient (eg. glucose). This requires protein pumps which use ATP for energy. Since energy is required, this is called active transport.

Osmosis: The Diffusion of Water

Exocytosis

PRACTICE! Complete the following on a separate page. 1) Sketch a labeled diagram of a membrane containing the following components:

phospholipids, glycolipids, cholesterol, transmembrane proteins (including active and passive transporters, and glycoprotein cell markers), a peripheral enzyme protein.

2) Write a paragraph or a series of paragraphs describing several different ways that cells have control over what enters and exits the cell membrane

3) Using a diagram, explain why the salinity of soil (level of salt) is an important factor for vegetable farmers to be aware of. Relate your answer to osmosis.

4) Why is there a need for both passive and active transport? Provide examples to illustrate your answer.