The Plasma Membrane -

1. The Plasma Membrane - Gateway to the Cell

2. Photograph of a Cell Membrane

3. Types of Transport Across Cell Membranes

4. Simple Diffusion • Requires NO energy • Molecules move from area of HIGH to LOW concentration

5. DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY

6. Diffusion of Liquids

7. Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW)

8. 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

9. Diffusion of H2O Across A Membrane High H2O potentialLow solute concentration Low H2O potentialHigh solute concentration

10. Cell in Isotonic Solution 10% NaCL90% H2O ENVIRONMENT CELL NO NET MOVEMENT 10% NaCL 90% H2O What is the direction of water movement? equilibrium The cell is at _______________.

11. Cell in Hypotonic Solution 10% NaCL90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement?

12. Cell in Hypertonic Solution 15% NaCL85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement?

13. Cells in Solutions

14. Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) CYTOLYSIS PLASMOLYSIS

15. Cytolysis & Plasmolysis Plasmolysis Cytolysis

16. Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic

17. isotonic hypotonic hypertonic hypertonic isotonic hypotonic

18. Three Forms of Transport Across the Membrane

19. 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.

20. 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.

21. Proteins Are Critical to Membrane Function

22. Active Transport • Requires energy or ATP • Moves materials from LOW to HIGH concentration • AGAINST concentration gradient

23. Active transport • Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. • Called Na+-K+ Pump

24. Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential

25. Moving the “Big Stuff” 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.

26. Exocytosis Exocytic vesicle immediately after fusion with plasma membrane.

27. Moving the “Big Stuff” Large molecules move materials into the cell by one of three forms of endocytosis.

28. Pinocytosis Most common form of endocytosis. Takes in dissolved molecules as a vesicle.

29. Pinocytosis • Cell forms an invagination • Materials dissolve in water to be brought into cell • Called “Cell Drinking”

30. Example of Pinocytosis mature transport vesicle pinocytic vesicles forming Transport across a capillary cell (blue).

31. Receptor-Mediated Endocytosis Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.

32. Receptor-Mediated Endocytosis

33. Endocytosis – Phagocytosis Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating”

34. Phagocytosis About to Occur

35. Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)

36. ExocytosisThe opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Cell environment