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

7. 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

8. Types of Membrane Proteins
Glycoproteins
Receptor proteins
Recognition proteins
Enzymatic proteins
Attachment proteins
Transport proteins
*KNOW THE FUNCTIONS! (pg. 84 in textbook)*

9. 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)

12. 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

13. REVIEW
Molecular workbench lipids and carbohydrates.

14. (review slide)

15. REVIEW
Head region of the lipid are polar molecules so they are attracted to water
Tails region of the lipid are nonpolar they repel water.
These molecular properties form the separation of inside and outside the cell.

16. 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

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

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

19. Diffusion

20. Diffusion Individual particles continuously move in random directions
Molecules moving from a greater concentration to a lower concentration
Ex: perfume, air freshener
Simple diffusion – substances pass through the membrane with no outside aid
Ex. substances: Oxygen, Carbon Dioxide, water and lipid soluble molecules

21. Diffusion Equilibrium !
Molecules are in constant motion they will continue to move until equilibrium is reached.
Equilibrium !
Outside cell
inside cell O2 O2 O2 O2
Diffusion video: O2 O2
Low Concentration
High Concentration

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

23. More diffusion -> “equilibrium”!!

24. Describe how oxygen and carbon dioxide move into and out of the lungs and extremities. Page 4 molecular workbench “diffusion, osmosis, active transport”

25. Osmosis

26. Osmosis
Diffusion of WATER from a high concentration to a low concentration across the cell membrane
Water moves DOWN its concentration gradient until equilibrium is reached

27. membrane water sugar solution 6
There are as many water molecules on the right as there are on the left but many of them are attached to sugar molecules and are not free to move.

28. Because there are more freely moving water molecules on 7
Sugar molecules can pass through the membrane but, being surrounded by a cloud of water molecules, they move more slowly.
Because there are more freely moving water molecules on
the left, more diffuse through the pores of the membrane from
left to right than from right to left.
Molecular movement

29. Iso – Hyper – Hypotonic Solutions

30. 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) (High solute, Low water)
Hypotonic: concentration of solute inside of cell is greater, water moves into cell (burst) (Low solute, High water)

31. Osmosis in animal cells11
so water diffuses into the cell
by osmosis
There is a greater concentration of free water molecules outside the cell than inside
and the cell swells up

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

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

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

35. Plasmolysis

36. Plants!
Plasmolysis = cell shrinks away from cell wall due to water loss ex: drought (low rain fall) causing plants to wilt
Turgid: swollen
Turgor pressure the rigidity of plant cells when they contain enough water so that the cell membrane exerts pressure on the cell wall.
Can tell turgor pressure is low when plant wilts

37. Osmosis: the diffusion of water as seen in class.
Size of a cell membrane can change as the amount of water inside changes in response to external conditions change.
Cells surrounded by “salt” water
Cells surrounded by “plain water”

38. Facilitated Diffusion

39. Facilitated Diffusion
Uses specific protein pores in the cell membrane to move certain “large” molecules from high concentration to low concentration.
Used for transport of water soluble molecules (hydrophillic). Ex: ions, amino acids (small proteins), and sugars
Carrier Protein - protein recognizes substance->changes shape->delivers substance to inside of the cell
Aquaporins – allow water to cross at a fast rate via faciliated diffusion

40. Ion Channels

41. 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

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

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

44. Active Transport

45. Sodium Potassium Pump pumps 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!

46. Endocytosis

47. 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

48. Exocytosis opposite of endocytosis!!