1. CELL MEMBRANE

2. http://upload. wikimedia

3. Two types of boundaries separate:
Cell Boundaries
Every cell is surrounded by a liquid environment
and has a liquid inside
Two types of boundaries separate:
Cell membrane (inner)
Thin, flexible layer that surrounds all cells
Cell wall (outer)
Strong supporting layer outside the cell membrane
Only in some organisms
(plants, algae, fungi, prokaryotes)
Porous

4. Phospholipids
Cell membranes are mostly built from fat molecules called phospholipids
Have a polar head and two nonpolar tails
Polar heads  attracted to water
Nonpolar tails  repelled by water
Movie #1

5. Lipid Bilayer
Because there is water inside and outside the cell, the phospholipids form a double layer called the lipid bilayer.
Polar heads on outside, nonpolar tails on the inside
Movie #2

6. Membrane Components
Membranes also have proteins embedded in the bilayer
act as tunnels or pumps across the membrane
others protect the cell membrane
Contains carbohydrates, usually attached to the proteins
act as signals to other cells
Contains cholesterol
Stabilizes the membrane

7. Cell Membrane

8. Figure 7-12 The Structure of the Cell Membrane
Section 7-3
Outside
of cell
Inside
(cytoplasm)
Cell
membrane
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains

9. Fluid Mosaic Model Lipid bilayer – double layer of molecules
Figure 7-12 The Structure of the Cell Membrane
Section 7-3
Lipid bilayer – double layer of molecules
Lipids are a certain class of C-H molecules
Do not like water ( think of oil + water) – the “tails”
The “heads” are polar molecules
Has proteins throughout
Can have carbohydrate “ID tags”
Moveable/fluid
Selectively Permeable
Inside of cell
(cytoplasm)
Cell
membrane
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains

10. Cell Wall
Cell wall – tough, porous boundary that lies outside the cell membrane; found in plant cells and in some bacteria but NOT in animal cells
Allow water, gases, and other substances to pass through easily
Most cell walls are made of carbohydrates and proteins
- Specifically composed of cellulose

11. FUNCTION of Cell Membrane
Regulates what goes in and
what comes out of a cell
Like a fence or a window screen
Regulation depends on size, concentrations, and the type of molecule trying to get through
Protects cell
Supports cell, but also flexible
Recognizes foreign material
Communicates with other cells

12. What goes in and out? (Transport)
Cell membrane is selectively permeable,
 it lets some things in, but not other things
Selection depends on…
size (smaller get through easily)
concentrations,
& type of molecule trying to get through
(lipid and nonpolar)
Substances keep moving till there are ~ equal amounts of them on both sides of the membrane
EQUILIBRIUM

13. Cell Membranes
Must be able to take in raw materials and eliminate waste products
Like a bouncer at a club

14. Permeability http://www. youtube. com/watch
Do these get through?
H+ or Ca++
CO2
K+, Cl-
H2O
Glycerol or ethanol (-OH) O2
Amino acids
Glucose