IX. Plasma Membrane A. Fluid Mosaic Model B. Cell Transport

1
IX. Plasma Membrane

• A. Fluid Mosaic Model
• B. Cell Transport

2
A. Fluid Mosaic Model

• 1. Singer Nicolson, 1972
• 2. Plasma membrane is a phospholipid bilayer with
  embedded proteins, cholesterol, glycolipids,
  glycoproteins
• 3. Embedded proteins shift through the bilayer
  membrane

3
2. Phospholipid Bilayer
4
3. Embedded Proteins

• a. Recognition proteins
• b. Transport proteins
• c. Receptor proteins

5
a. Recognition proteins

• 1.) Contact signaling- recognition
  identification of other cells
• 2.) Recognize foreign cells or material tag
  them for destruction
• 3.) Contact inhibition

6
b. Transport proteins

• 1.) Electrical signaling- channel/gate proteins
  open or close based on the charge of the membrane
• 2.) Regulate H2O soluble ions molecules through
  the membrane

7
c. Receptor proteins

• 1.) Chemical signaling- specific molecule
  (ligand) binds to protein causing a chemical
  change
• 2.) Set-off response when ligand binds to them
• 3.) Secondary messengers

8
B. Cellular Transport

• 1. Movement of material into out of the cell
  through the plasma membrane
• 2. Energy neutral (Passive transport)- movement
  with a concentration, electrical, or pressure
  gradient
• 3. Energy negative- movement against the
  concentration gradient

9
2. Energy Neutral

• a. Diffusion
• b. Osmosis
• c. Facilitated Diffusion

10
a. Diffusion

• 1.) Net random movement of a substance from areas
  of greater concentration to areas of lesser
  concentration
• 2.) Dissolved gases (O2 CO2) lipid soluble
  molecules across cell membrane
• 3.) Ions across cell membrane through channel
  proteins
• 4.) Factors affecting diffusion

11
4.) Diffusion Factors

• 1.) Temperature
• 2.) Molecular mass volume
• 3.) Medium
• 4.) Concentration Gradient
• 5.) Membrane permeability

12
b. Osmosis

• 1.) Diffusion of solvent through a differentially
  permeable membrane
• 2.) Results from differing concentrations of
  solvent solute across the membrane
• 3.) Aquaporins- water channel proteins
• 4.) Isotonic
• 5.) Hypotonic
• 6.) Hypertonic

13
4.) Isotonic
14
4.) Isotonic

• a.) No net movement of water into or out of the
  cell

15
5.) Hypotonic
16
5.) Hypotonic

• a.) Net movement of water into the cell
• b.) Turgor pressure- plant cells swell maintain
  structural integrity as water pushes against the
  cell wall
• c.) Cytolysis- bursting of an animal cell in a
  hypotonic solution, hemolysis

17
6.) Hypertonic
18
6.) Hypertonic

• a.) Plasmolysis- plant cells plasma membrane
  pulling away from its cell wall as the central
  vacuole loses H2O
• b.) Crenation- the shrinking of cells in a
  hypertonic solution, especially RBCs, plasma
  membrane drapes over the cytoskeleton

19
c. Facillitated Diffusion

• 1.) Diffusion assisted by transport proteins
• 2.) Requires no ATP
• 3.) Water-soluble molecules (glucose proteins)
  and ions (K Ca2)

20
3. Energy negative

• a. Active Transport
• b. Exocytosis
• c. Endocytosis

21
a. Active Transport

• 1.) Uses transport proteins activated by ATP
• 2.) Individual molecules or ions, Na/K pump

22
b. Exocytosis

• 1.) Material enclosed in membrane vesicle
• 2.) Vesicle moves to cell membrane, fuses,
  opens
• 3.) Contents diffuses away

23
c. Endocytosis

• 1.) Pinocytosis
• 2.) Phagocytosis
• 3.) Receptor Mediated Transport

24
1.) Pinocytosis

• a.) Dimpling on the exterior of cell membrane
• b.) Vesicle forms surrounding extracellular fluid
• c.) Movement of vesicle fluid into the cell

25
2.) Phagocytosis

• a.) Formation of cytoplasmic extensions,
  pseudopodia
• b.) Particle or organism surrounded
• c.) Vesicle formed moved into the cell
• d.) Amoeba sp, monocytes, neutrophils

26
2.) Phagocytosis
27
3.) Receptor Mediated Transport

• a.) Specific molecule (ligand) binds with
  receptor protein
• b.) RP-SM (RL) complex migrates toward a dimple
  (pinocytosis)
• c.) Vesicle formed moved into the cell

28
Return to Lectures Menu