CH. 5 - MEMBRANES

        I. CELL MEMBRANE - Plasma membrane (PM)

            A.  FLUID-MOSAIC MODEL.  "Proteins in a sea of phospholipids." (p. 90)

                  1. Phospholipid bilayer = sea/fluid

                  2. Proteins = float like boats

            B.  FUNCTION

                  1.  Shape

                  2.  Support

                  3.  Selectively permeable

            C.  P.M. PROTECTION

                  1. Animal - cell coat, glycocalyx; recognition & binding to of:

                        a. food 

                        b. friend/foe

                  2.  Plant - cell walls 

                        a. outside p.m.

                        b. thick and strong

                        c. cellulose & pectin.

                        d. lignin: structure & turgor (H2O Pressure)

        II.WATER POTENTIAL - H₂O tends to move from a hi [H₂O] èlow [H₂O].

                  Solution with highest [H₂O] has highest water potential

        III. PASSIVE TRANSPORT  - No energy expended, [HI]è [LO], with/down gradient

A.   DIFFUSION - Random movement leading to equal distribution

1.    Fastest with gases, then liquids.   (p. 96)

2.     With or without membrane.

B.   FACILITATED DIFFUSION - Carrier protein assists transport. (p. 97)

C.   OSMOSIS - Diffusion of liquid (usually H₂O) across a selectively

                                    permeable membrane. (p. 98)

            Osmotic potential - measure of tendency of water to move (Hi [H₂O]

                                                  across a selectively permeable membrane.

1.    Isotonic: Equal [ ] on both sides, no net movement     (p. 99)

2.    Hypertonic:  High [ ] of solute, low [ ] of water.

3.    Hypotonic:  Low [ ] of solute, hi [ ] of water.

4.    "Don't drink salt water" example.

5.    Canned fruit example.

        IV. ACTIVE TRANSPORT - of SMALL molecules & ions

                  1. [LO] è [HI], against gradient, "uphill"

                  2. Requires energy - ATP

                  3. Requires carrier protein

A.   Glucose

B.   Na⁺/K⁺ exchange pump            (p. 100)

C.   Co-transport/coupled transport (p. 101)

D.   Proton (H⁺) pump

        V. TRANSPORT OF LARGER SUBSTANCES - requires ATP

                  A.  ENDOCYTOSIS - movement in (p. 102)

                              1. Phagocytosis - cell eating

                                          a. largest particles 

                                          b. bacteria & other cells

                              2.  Pinocytosis - cell drinking, molecules, smaller things

                              3.  Receptor or Vesicle-mediated endocytosis

                                          a. uptake of very specific molecules.

                                          b. coated pits

                  B.  EXOCYTOSIS - cell exiting, opposite of endocytosis.  (p. 103)

                              1. waste elimination

                              2. product release

        VI.  CELL COMMUNICATION

                  A. Animal - gap junction (p. 83)

                  B. Plant - plasmodesmata (p. 85)

         VII - SUMMARY - ***KNOW TABLE 5.2 (p. 104)