1. The Cell Membrane: Phospholipid Bilayer

2. Learning Objectives What is diffusion
What are the unique features for the cell membrane (be able to draw it too)
Why must a cell membrane also have proteins
What different Roles do membrane proteins serve

3. Simple Diffusion pg185
Movement of substances from regions of higher concentration to regions of lower concentration
Diffusion of water across a membrane is called OSMOSIS
Can also apply to oxygen, CO2 and lipid-soluble substances

4. The Cell Membrane: Phospholipid Bilayer
Pg 182
The Cell Membrane: Phospholipid Bilayer

5. Phospholipids – Makes up the cell membrane
This O–Atom has a
negative charge
This N–Atom has a
positive charge

6. Phospholipids- makes up the cell membrane
This N–Atom has a
positive charge
This O–Atom has a
negative charge
Phospholipids- makes up the cell membrane

7. Hydrophilic vs. Hydrophobic
Hydrophilic = Water loving
Hydrophobic = Water fearing

8. Phospholipids and water
Remember: water has
POLAR covalent bonds

9. Charges on the Phosphate & Nitrogen makes the head region hydrophilic
(likes water)
The Tails have no charge, they are just long carbohydrate chains (like other lipids) that are non-polar so they are hydrophobic (hates water) and so they will only interact with other non-polar molecules like other lipids (cholesterol) and each other (tails always face each other)
The Phospholipid Bilayer is a key part of the Fluid Mosaic Model that makes up the outer most layer of cells.

10. The Phospholipid Bilayer is a key part of the Fluid Mosaic Model that makes up the outer most layer of cells.
Helps controls what moves in and out of cell (food, wastes, viruses)
Cholesterol (lipid) stabilizes the membrane

11. This Selective Permeability of the membrane means that: 1
This Selective Permeability of the membrane means that: 1. Some things can cross freely (in or out) 2. Some things are never allowed to cross at all 3. And some things need assistance to cross the membrane…

12. ….certain proteins “sit” in the bilayer and help with interaction between the outside environment and the internal areas of the cell. These are called Transport Proteins

13. Transport Proteins Transport proteins can act like:
Channels (no energy needed)  FACILITATED DIFFUSION
Carriers (no energy needed)  like water wheels: not in picture
Pumps (needs energy)  going against the flow called: ACTIVE TRANSPORT
Transport Proteins

14. (energy)
(Channel protein)
Transport Proteins

16. Other Membrane proteins
Channels, carriers, pumps
Receptors (muscle, nerve cells)
Enzymes (start or stop enzyme from working)
Self-markers (identifies the cell to other cells)
“Anchors” to other cells

17. Look under “Lipids” &“Membrane Transport”
NA – K+ Pump protein
Look under “Lipids” &“Membrane Transport”

18. Intercellular Junctions
Tight junctions
close space between cells
located among cells that form linings
Intercellular Junctions
Desmosomes
form “spot welds” between cells
located among outer skin cells
Gap junctions
tubular channels between cells
located in cardiac muscle cells
End

19. Crossing…………………………….…Over