1. Standard B-2.2

2.  The process of maintaining balance in an organism’s internal environment.  Essential to the survival of a cell.  Maintaining homeostasis a primary job of the plasma membrane. (does this by being semipermeable)

3.  Defined as a flexible boundary between a cell and it’s environment.  ALL prokaryotic and eukaryotic cells have a plasma membrane to separate them from their watery environment.  The membrane allows nutrients into the cell and allows waste and other products to leave the cell.

4.  The plasma membrane has the property of selective permeability.  (also called semipermeable)  This is how homeostasis is maintained.  Means:  Allows some substances to pass through to the inside  Does not allow some substances to pass though to the inside  Doesn’t allow just anything to leave the cell either.  It is selective in what it lets enter and leave the cell

5. Fish net Coffee filter Flour sifter Gold Mining too

6. Most of the molecules in the PM are phospholipids.

7.  PM is composed of a phospholipid bilayer.  (2 layers of phospholipids are arranged tail-to- tail.)

8.  Each phospholipid is diagramed as a head with 2 tails.

9.  Heads:  made polar by the phosphate group  Is attracted to water bc water is polar too  Hydrophilic = water loving  Tails:  Nonpolar  Repelled by water  Hydrophobic = water fearing

10.  The layers make a sandwich so that the fatty acid tails make up the inner most portion of the PM.  Water loving heads are in contact with the water inside of the cell and the watery outside of the cell.  Water fearing tails are farthest away from the water they hate.  Not touching the water on the inside or the outside of the cell.

11.  Moving with and among the phospholipids are: - cholesterol - carbohydrates - proteins

12.  Cholesterol: -prevents the fatty-acid tails from sticking together. - contributes to the fluidity of the pm. (A high cholesterol diet is not advised, but cholesterol plays a critical role in membrane structure.)

13.  Carbohydrates: - Stick out from pm to define the cell’s characteristics - Helps cells identify chemical signals. (Carbs in membrane might help disease-fighting cells recognize and attack a potentially harmful cell.)

14.  Proteins: -2 types of proteins found in PM 1. peripheral proteins 2. integral proteins

15.  Peripheral proteins: proteins that do not protrude from the inside of the cell to the outside of the cell.  Outer surface: called receptors and they transmit signals from outside the cell to the inside of the cell  Inner surface: anchor the pm to the cells internal support structure, gives the cell it’s shape.

16.  Integral proteins: span the entire membrane, creating tunnels through which certain substances can enter and leave the cell.  Move needed substances in  Move wastes out Also called: Transport proteins

17.  The phospholipids in the bilayer create a “sea” in which other molecules can float, like apples floating in a barrel of water.  “sea” concept is the basis for the fluid mosaic model of the pm.  The phospholipids can move sideways w/i the membrane, just as the apples move around in the barrel.

18.  At the same time, other components in the membrane, like proteins, also move among the phospholipids.  Because there are different substances in the pm, a pattern, or mosaic is created on the surface.  The components of the pm are in constant motion, sliding past each other.

19.  Fluid: particles that can change position w/o separating.  Mosaic: picture or pattern made of small pieces of different colors and/or shapes.

20.  What is the main function of the Plasma Membrane?

21.  What name has been given to the sea-like movements of the plasma membrane?

22.  What does hydrophobic mean?

23.  Besides phospholipids, what is another structure you may see in a plasma membrane and what is that structures function within the membrane?

24.  What does hydrophilic mean?

25.  What do we call the 2 layers of phospholipids arranged tail to tail?