Diffusion, Osmosis & Cell Membrane

V. Diffusion & Osmosis
Example 2
-Solution 0.4 M sugar
-Cell 1.0 M sugar
Water goes into the cell by osmosis

When will water movement stop (net) ?
1. when concentrations solutes are equal (Isotonic);
2. when cell would bursts;
3. when the cell fills enough to create a positive pressure that cancels out the force of Osmosis. (Pressure cancels Osmosis) - This is called Turgor Pressure

VI. The properties of the cell membrane ( The fluid mosaic model ) 

Composed of phospholipids, cholesterol (structural) and proteins (functional)

Functional Proteins:

 A. Channels :

1. Aquaporins (dedicated of movement of water)
2. Ion channels (devoted to Na+, Cl-, Ca2+, K+, etc.)

B. Carriers - Could be either active or passive. One molecule could be carried against the force of diffusion (ATP must be burned) or with the force of diffusion

C. Markers - Identify the cell as your own and also identify it as the type of cell

D. Pumps :

1. Proton Pump - pumps H ions to 1 side of the membrane , creating a proton gradient that is used by ATP (synthase to make ATP)
2. Sodium-Potassium Pump - uses ATP to pump Na+ out of the cell (neurons) and K+ ions back into the cell. Uses the energy from ATP to cause the protein to change its tertiary structure