1. Why is the cell membrane so important???

3. Selectively permeable membrane Semi permeable membrane
Names!
Cell membrane
Plasma membrane
Selectively permeable membrane
Semi permeable membrane

4. Functions of the Cell Membrane
Protects the cell
Regulates what goes in and out of cell
Helps to communicate with other cells
Creates attachments between cells
Dynamic!
**Maintains HOMEOSTASIS in the cell**

5. Structure of the Cell Membrane
Phospholipid bilayer – double layered sheet
Properties of the lipids determine the properties of the membrane:
Hydrophobic (“water-fearing”) = tails
Hydrophilic (“water-loving”) cluster together = heads
Heads DO touch water, tails DO NOT touch water

6. Fluid Mosaic Model dev. By Singer & Nicolson 1972
Proteins move within layers of lipids w/I viscous fluid
Transport
Structure
Hydrogen bonds can form between water and phospholipid heads inside and outside of cell
The more double bonds there are in the tails the more fluid the membrane
Incr. in temp. causes membr. To be more fluid (because mol. Move faster)
Decr. Temp. (mol. Move slower -> less fluid)

9. Selectively Permeable
Some substances can pass, others cannot pass
Most substances can pass
Substances that are too big or charged cannot cross the bilayer
Therefore, cells need different means of TRANSPORT to move these substances into and out of the cell

10. Vocabulary Terms
Solution- mixture in which one or more substances are UNIFORMLY distributed in another. “homogenous solution”
Solute- what gets dissolved.
Solvent- what does the dissolving.
Ex. salt water:
salt is solute
water is solvent.
Ex. Ice tea
Mix is solute
Water is solvent

11. Movement from a high concentration to a low concentration!
Passive Transport
Requires NO energy!!
Movement from a high concentration to a low concentration!

12. Passive Transport 1. diffusion 2. osmosis 3. facilitated diffusion
4. diffusion through ion channels

13. Diffusion

14. Diffusion
Molecules moving from a greater concentration to a lower concentration
Ex: perfume
Simple diffusion – substances pass through the membrane with no outside aid
Ex. substances: Oxygen, Carbon Dioxide, water and lipid soluble molecules

15. Vocabulary
Concentration gradient: difference in concentrations (amount of solute)
Equilibrium: particles/molecules are equal on both sides of membrane

16. More diffusion -> “equilibrium”!!

17. Osmosis

18. Osmosis
Movement of WATER from a high concentration to a low concentration across the cell membrane

19. Iso – Hyper – Hypotonic Solutions

20. Vocabulary
Isotonic: concentration inside and outside of cell are the same  no net diffusion
Hypertonic: when concentration of solute outside of cell is greater, water moves out of cell (shrink)
Hypotonic: concentration of solute inside of cell is greater, water moves into cell (burst)

21. Where is there more water?
Which way will it move?
Type of Solution?
Out of the cell
Into the cell
Hypotonic Solution

22. Where is there more water?
Which way will it move?
Type of Solution?
Equal
No net movement
Isotonic Solution

23. Where is there more water?
Which way will it move?
Type of Solution?
In the cell
Out of the cell
Hypertonic Solution

24. Plasmolysis

25. Plants!
Plasmolysis = cell shrinks away from cell wall due to water loss ex: drought (low rain fall) causing plants to wilt
Turgor Pressure = cell wall sustains shape, otherwise would explode

26. Facilitated Diffusion

27. Facilitated Diffusion
Carrier Protein –
-protein recognizes substance->changes shape->delivers substance to inside of the cell
Facilitated Diffusion: water soluble molecules (hydrophillic). Ex: ions, amino acids (small proteins), and sugars

28. Ion Channels

29. Ion channels -allows ions Ca2+ and Cl- to enter cell
Some are open all the time
Others are gated and will open when
Cell membrane stretches
Electrical signals
Chemical signals

30. Movement from a LOW concentration to a HIGH concentation!
Active Transport
REQUIRES ENERGY!
Movement from a LOW concentration to a HIGH concentation!

31. Active Transport
1. Sodium Potassium Pump
2. Endocytosis
3. Exocytosis

32. Active Transport

33. Sodium Potassium Pump -pumps like to keep ions in balance
3 Na+ out for every 2 K+ in
This creates a build up of Na+ outside cell and K+ inside cell forming a net electrical charge across the membrane
Allows for nerve impulses
Contraction of muscles
1/3 of all energy in animal cells goes to running this pump even as we sleep!

34. Endocytosis

35. Endocytosis
Take in external fluid, macromolecules and other large particles.
Forms “vesicle” some fuse with lysosomes (digestion) others fuse with membrane of other organelles.
2 Types: a) pinocytosis – cell drinking fluid
b) phagocytosis – cell eats

36. Exocytosis opposite of endocytosis!!