1. Homeostasis Balanced internal condition of cells
The Plasma Membrane
4/19/2017
Homeostasis
Balanced internal condition of cells
Also called equilibrium
Maintained by plasma membrane controlling what enters & leaves the cell
G. Podgorski, Biol. 1010

2. Cell Membrane Hydrophobic molecules pass easily; hydrophilic DO NOT
The Plasma Membrane
Cell Membrane
4/19/2017
The cell membrane is made of 2 layers of phospholipids called the lipid bilayer
Hydrophobic molecules pass easily; hydrophilic DO NOT
G. Podgorski, Biol. 1010

3. The Plasma Membrane
4/19/2017
Solubility
Materials that are soluble in lipids can pass through the cell membrane easily
G. Podgorski, Biol. 1010

4. Semipermeable Membrane
The Plasma Membrane
Semipermeable Membrane
4/19/2017
Small molecules and larger hydrophobic molecules move through easily.
e.g. O2, CO2, H2O
G. Podgorski, Biol. 1010

5. Semipermeable Membrane
The Plasma Membrane
Semipermeable Membrane
4/19/2017
Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own.
G. Podgorski, Biol. 1010

6. Types of Transport Across Cell Membranes
The Plasma Membrane
4/19/2017
Types of Transport Across Cell Membranes
G. Podgorski, Biol. 1010

7. Simple Diffusion Requires NO energy
The Plasma Membrane
4/19/2017
Simple Diffusion
Requires NO energy
Molecules move from area of HIGH to LOW concentration
G. Podgorski, Biol. 1010

8. The Plasma Membrane
4/19/2017
DIFFUSION
Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY
G. Podgorski, Biol. 1010

9. Diffusion of Liquids The Plasma Membrane 4/19/2017
G. Podgorski, Biol. 1010

10. Diffusion through a Membrane
The Plasma Membrane
4/19/2017
Diffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient (HIGH to LOW)
G. Podgorski, Biol. 1010

11. Diffusion across a membrane Semipermeable membrane
The Plasma Membrane
4/19/2017
Osmosis
Diffusion across a membrane
Diffusion of water across a membrane
Moves from HIGH water potential (low solute) to LOW water potential (high solute)
Semipermeable membrane
G. Podgorski, Biol. 1010

12. Diffusion of H2O Across A Membrane
The Plasma Membrane
4/19/2017
Diffusion of H2O Across A Membrane
High H2O potential Low solute concentration
Low H2O potential High solute concentration
G. Podgorski, Biol. 1010

13. Aquaporins Water Channels Protein pores used during OSMOSIS
The Plasma Membrane
4/19/2017
Aquaporins
Water Channels
Protein pores used during OSMOSIS
WATER MOLECULES
G. Podgorski, Biol. 1010

14. Cell in Isotonic Solution
The Plasma Membrane
4/19/2017
Cell in Isotonic Solution
10% NaCL 90% H2O
ENVIRONMENT
CELL
NO NET MOVEMENT
10% NaCL
90% H2O
What is the direction of water movement?
equilibrium
The cell is at _______________.
G. Podgorski, Biol. 1010

15. Cell in Hypotonic Solution
The Plasma Membrane
4/19/2017
Cell in Hypotonic Solution
10% NaCL 90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement?
G. Podgorski, Biol. 1010

16. Cell in Hypertonic Solution
The Plasma Membrane
4/19/2017
Cell in Hypertonic Solution
15% NaCL 85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
G. Podgorski, Biol. 1010

17. Cells in Solutions The Plasma Membrane 4/19/2017
G. Podgorski, Biol. 1010

18. NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
The Plasma Membrane
4/19/2017
Isotonic Solution
Hypotonic Solution
Hypertonic Solution
NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
CYTOLYSIS
PLASMOLYSIS
G. Podgorski, Biol. 1010

19. Cytolysis & Plasmolysis
The Plasma Membrane
4/19/2017
Cytolysis & Plasmolysis
Cytolysis
Plasmolysis
G. Podgorski, Biol. 1010

20. Osmosis in Red Blood Cells
The Plasma Membrane
4/19/2017
Osmosis in Red Blood Cells
Isotonic
Hypertonic
Hypotonic
G. Podgorski, Biol. 1010

21. isotonic hypotonic hypertonic hypertonic isotonic hypotonic
The Plasma Membrane
4/19/2017
isotonic
hypotonic
hypertonic
hypertonic
isotonic
hypotonic
G. Podgorski, Biol. 1010

22. Three Forms of Transport Across the Membrane
The Plasma Membrane
Three Forms of Transport Across the Membrane
4/19/2017
G. Podgorski, Biol. 1010

23. Passive Transport Simple Diffusion Doesn’t require energy
The Plasma Membrane
4/19/2017
Passive Transport
Simple Diffusion
Doesn’t require energy
Moves high to low concentration
Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out.
G. Podgorski, Biol. 1010

24. Facilitated diffusion
The Plasma Membrane
4/19/2017
Passive Transport
Facilitated diffusion
Doesn’t require energy
Uses transport proteins to move high to low concentration
Examples: Glucose or amino acids moving from blood into a cell.
G. Podgorski, Biol. 1010

25. Proteins Are Critical to Membrane Function
The Plasma Membrane
4/19/2017
Proteins Are Critical to Membrane Function
G. Podgorski, Biol. 1010

26. Types of Transport Proteins
The Plasma Membrane
4/19/2017
Types of Transport Proteins
Channel proteins are embedded in the cell membrane & have a pore for materials to cross
Carrier proteins can change shape to move material from one side of the membrane to the other
G. Podgorski, Biol. 1010

27. Facilitated Diffusion
The Plasma Membrane
4/19/2017
Facilitated Diffusion
Molecules will randomly move through the pores in Channel Proteins.
G. Podgorski, Biol. 1010

28. Facilitated Diffusion
The Plasma Membrane
4/19/2017
Facilitated Diffusion
Some Carrier proteins do not extend through the membrane.
They bond and drag molecules through the lipid bilayer and release them on the opposite side.
G. Podgorski, Biol. 1010

29. The Plasma Membrane
4/19/2017
Carrier Proteins
Other carrier proteins change shape to move materials across the cell membrane
G. Podgorski, Biol. 1010

30. Active Transport Requires energy or ATP
The Plasma Membrane
4/19/2017
Active Transport
Requires energy or ATP
Moves materials from LOW to HIGH concentration
AGAINST concentration gradient
G. Podgorski, Biol. 1010

31. The Plasma Membrane
4/19/2017
Active transport
Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients.
Called Na+-K+ Pump
G. Podgorski, Biol. 1010

32. Sodium-Potassium Pump
The Plasma Membrane
4/19/2017
Sodium-Potassium Pump
3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential
G. Podgorski, Biol. 1010

33. Exocytosis- moving things out.
The Plasma Membrane
Moving the “Big Stuff”
4/19/2017
Exocytosis- moving things out.
Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.
This is how many hormones are secreted and how nerve cells communicate with one another.
G. Podgorski, Biol. 1010

34. The Plasma Membrane
Exocytosis
4/19/2017
Exocytic vesicle immediately after fusion with plasma membrane.
G. Podgorski, Biol. 1010

35. The Plasma Membrane
Moving the “Big Stuff”
4/19/2017
Large molecules move materials into the cell by one of three forms of endocytosis.
G. Podgorski, Biol. 1010

36. Pinocytosis Most common form of endocytosis.
The Plasma Membrane
Pinocytosis
4/19/2017
Most common form of endocytosis.
Takes in dissolved molecules as a vesicle.
G. Podgorski, Biol. 1010

37. Pinocytosis Cell forms an invagination
The Plasma Membrane
4/19/2017
Pinocytosis
Cell forms an invagination
Materials dissolve in water to be brought into cell
Called “Cell Drinking”
G. Podgorski, Biol. 1010

38. Example of Pinocytosis
The Plasma Membrane
Example of Pinocytosis
4/19/2017
mature transport vesicle
pinocytic vesicles forming
Transport across a capillary cell (blue).
G. Podgorski, Biol. 1010

39. Receptor-Mediated Endocytosis
The Plasma Membrane
4/19/2017
Receptor-Mediated Endocytosis
Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.
G. Podgorski, Biol. 1010

40. Receptor-Mediated Endocytosis
The Plasma Membrane
Receptor-Mediated Endocytosis
4/19/2017
G. Podgorski, Biol. 1010

41. Endocytosis – Phagocytosis
The Plasma Membrane
4/19/2017
Endocytosis – Phagocytosis
Used to engulf large particles such as food, bacteria, etc. into vesicles
Called “Cell Eating”
G. Podgorski, Biol. 1010

42. Phagocytosis About to Occur
The Plasma Membrane
Phagocytosis About to Occur
4/19/2017
G. Podgorski, Biol. 1010

43. The Plasma Membrane
4/19/2017
Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)
G. Podgorski, Biol. 1010

44. The Plasma Membrane
4/19/2017
Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane.
Inside Cell
Cell environment
G. Podgorski, Biol. 1010

45. The Plasma Membrane
4/19/2017
G. Podgorski, Biol. 1010