2. The Plasma Membrane = The Cell Membrane

3. The Most Important Job…
Maintaining HOMEOSTASIS
Homeostasis = internal balance
All living cells must maintain balance

4. How does it maintain homeostasis?
The plasma membrane controls what goes in and out
Like a good bouncer

5. How does it maintain homeostasis?
a). allow a steady supply of water, glucose, amino acids, and lipids to come into the cell.
b). remove excess amounts of these nutrients when levels get so high that they are harmful.
c). allow waste and other products to leave the cell.

6. Selectively Permeable Membrane
Allows some substances to cross and not others
sugar
H2O
salt
waste
lipids

7. Selectively Permeable Membrane
Small uncharged polar particles may pass
Large uncharged polar molecules and ions cannot pass

8. Structure Of The Plasma Membrane

9. Structure Of The Plasma Membrane
Phospholipid bilayer
2 layers of lipids
Phosphate head - Hydrophilic - Polar
Fatty acid tail - Hydrophobic - Non polar

10. To make the cell membrane, phospholipids come together to make two layers
Which option makes the most sense? WHY? A B C

11. Structure Of The Plasma Membrane
Membrane Proteins
Transport channels
Chemical receptors
Cell to cell communication

12. Structure Of The Plasma Membrane

13. Structure Of The Plasma Membrane
Cholesterol
Keep the phospholipids spaced apart
Keeps the membrane fluid/flexible

14. Structure Of The Plasma Membrane
Surface Carbohydrates
Cell signaling
Cell recognition
Cell adhesion

15. Show me…part of your membrane

16. Which part forms the bilayer?

17. Which part helps with transport?

18. Which part keeps the membrane fluid?

19. Which part functions in cell signaling?

20. That is one smelly balloon
Eww…
That is one smelly balloon

21. How do the smells get out of the balloons?

22. The balloon is a semipermeable membrane

23. Molecules small enough to fit through the “holes” in the balloon diffuse through the membrane

24. Remember Smelly Balloons?
Just like the balloon the cell membrane is selectively or semi permeable
This means only some things can diffuse through the cell membrane
Now lets talk more about diffusion…

25. Types of Transport
Two types of cellular transport:
Passive
Active

26. Passive Transport -Requires NO Energy -Diffusion
-Molecules move from an area of HIGH concentration to an area of LOW concentration
-With the concentration gradient
-Diffusion
-Facilitated Diffusion
-Osmosis

27. Important Vocabulary
Solute - The solid substance that is dissolved in a solvent.
Solvent - The liquid substance in which the solute is dissolved.
Solution - The mixture of two or more substances (solute and solvent) in which the molecules of the substances are evenly distributed.

28. Diffusion
The passive movement of molecules from an area of high concentration to an area of low concentration

29. Fun With Food Coloring

32. Facilitated Diffusion
Diffusion where a protein carrier molecule or channel helps transport molecules across the membrane

33. Osmosis The diffusion of water across a selectively permeable membrane
Water moves from an area of high water concentration to an area of low water concentration
Water moves to where there are MORE solute molecules

34. Where are the solute ions more concentrated?
Which way will the Cl- and Na+ ions move?

36. Hypertonic solution Hypotonic solution Isotonic solution
Osmosis occurs in 3 types of solutions.
Hypertonic solution
Hypotonic solution
Isotonic solution

37. Hypertonic Environment
Osmosis = The diffusion of water across a membrane.
Water
moves
OUT
Hypertonic Environment
An environment with a more solute concentration compared to another
97% NaCl
3% H2O
3% NaCl
97% H2O

38. Hypertonic Environment
Cell will Shrink
Hypertonic Environment

39. Hypotonic Environment
Osmosis = The diffusion of water across a membrane.
Water
moves IN
Hypotonic Environment
An environment with a less solute concentration compared to another
3% NaCl
97% H2O
97% NaCl
3% H2O

40. Hypotonic Environment
Cell will Lyse (Swell)

41. Osmosis = The diffusion of water across a membrane.
moves
IN & OUT
Isotonic Environment
An environment with equal solute concentration compared to another
3% NaCl
97% H2O
3% NaCl
97% H2O

42. Isotonic Environment
Cell will
Stay the same

44. Which way will the water diffuse?
What type of solution is in each beaker?
Hypertonic
Isotonic
Hypotonic

45. Gummy Bear Lab - Day 1
Not for eating!
Okay…maybe when we’re finished

46. Types of Transport
Two types of cellular transport:
Passive
Active

47. Active Transport -Requires Energy -Endocytosis -Exocytosis
-Molecules move from an area of LOW concentration to an area of HIGH concentration
-Against the concentration gradient
-Endocytosis
-Exocytosis
-Protein Pump

48. Endocytosis and Exocytosis

49. Exocytosis and Endocytosis are ways a cell can pass proteins out of or into the cell. Exocytosis-a membrane bound vesicle, fuses with the membrane, and releases its contents outside the cell Endoocytosis-the cell membrane engulfs (“eats”) molecules, and takes them into the cell

50. Use energy to pump ions from low concentration to high concentration
Protein Pump
Use energy to pump ions from low concentration to high concentration