1. CELL MEMBRANE Selectively permeable Physical isolation
Regulation of exchange with environment
Sensitivity
Structural support

2. MEMBRANE STRUCTURE
Phospholipids (phosphate group bonded to a diglyceride) – form a bilayer
Cholesterol (lipid)
Proteins – partially embedded (peripheral) or totally spanning (integral)
Carbohydrates – glycocalyx – act as adhesive, receptor area, ID system

3. MEMBRANE PROTEINS
Receptors – receive chemicals at binding site – triggers change in cell activity
Channel – allow H2O to get through lipid bilayer
Carrier – transport solutes across membrane
Enzymes
Anchor – attach + stabilize cell membrane
Identifier – identifies cell as “self”

4. MEMBRANE TRANSPORT
Can be passive or active

5. PASSIVE TRANSPORT No energy requirement DIFFUSION
The net movement of molecules from >[ ] to < [ ]
Determined by lipid solubility (alcohol, fatty acids, steroids, O2, CO2)
Molecules move DOWN their concentration gradient

6. 2. OSMOSIS Diffusion of H2O across a membrane
H2O moves from areas of high [H2O] to low [H2O]
OR low [solute} to high [solute]
Isotonic
Hypotonic (hemolysis results)
Hypertonic (crenation)

7. 3. FACILITATED DIFFUSION
Transported molecule binds to receptor site, protein carrier (integral protein) undergoes a conformational change, allowing molecule to enter cell
Carriers are specific
EX – glucose into cell

8. ACTIVE TRANSPORT Requires ATP
Moves a substance (molecule, ion) against its concentration (or electrochemical) gradient
Requires a carrier protein

9. 1. SOLUTE PUMPING Against concentration gradient
Movement of most amino acids and ions
Requires a carrier protein (specific)
EX. Na+/K+ pump (exchange pump)

10. 2. EXOCYTOSIS Secretion of substances from cell
Substance is enclosed in a membranous vesicle which fuses with the CM
EX. Neurotransmitters, hormones, mucus, etc; ejection of cell waste

11. 3. EXOCYTOSIS A.PHAGOCYTOSIS
Type of endocytosis
“cell eating”
Large external particle (proteins, bacteria, dead cell debris) surrounded by a pseudopod and becomes enclosed in a membranous sac
EX. WBCs and macrophages

12. B. PINOCYTOSIS Type of endocytosis “cell drinking”
CM surrounds an external droplet containing small solutes; membrane edges fuse, forming a fluid filled vesicle EX. Absorptive cells of the intestines and kidneys

13. C. RECEPTOR MEDIATED ENDOCYTOSIS
External substances bind to specific membrane receptors and form a “coated pit”
EX. Intake of some hormones, cholesterol, iron and others