Cellular Transport Notes

1. Cellular Transport Notes Ch. 7.2 Plasma Membrane (p.175-178) Ch. 8.1 Cellular Transport (p.195-200)

2. Cell Membranes • ALL cells have a Cell Membrane • Functions: • Controls what enters and exits the cell to maintain an internal balance called homeostasis • Provides protection and support for the cell TEM picture of a real cell membrane.

3. Cell Membranes (continued) • Structure of cell membrane Lipid Bilayer -2 layers of phospholipids • Phosphate head is polar (water loving) • Fatty acid tails non-polar(water fearing) • Proteins embedded in membrane Phospholipid Lipid Bilayer

4. Fluid Mosaic Model of the cell membrane Polar heads love water & dissolve. Membrane movement animation Non-polar tails hide from water. Carbohydrate cell markers Proteins

5. Cell Membranes (continued) • 4. Cell membranes have pores (holes) in it which makes it Selectively Permeable: Allows some molecules in and keeps other molecules out (the structure helps it be selective!!) Pores

6. Structure of the Cell Membrane Outside of cell Carbohydrate chains Proteins Lipid Bilayer Transport Protein Phospholipids Inside of cell (cytoplasm) Animations of membrane structure Go to Section:

7. Cell Membrane “Use Textbook” • ANSWER THE FOLLOWING: • 1. What is the function of the cell membrane? (p. 175) • 2. Describe the structure of the cell membrane? (p. 176) • 3. How many layers of lipids are there in the plasma membrane? (p. 177) • 4. What are the proteins called that are found within the plasma membrane? (p.177) • Why is the structure of the cell membrane referred to as a “mosaic?”? (p.178)

8. Cell Concentrations • Cells are surrounded and filled with a liquid environment • The cytoplasm contains a solution of different substances.

9. Cell Concentrations • A solution is a mixture of two or more substances. • Solute – dissolved substance (salt/sugar) • Solvent – dissolves solute (water)

10. Cell Concentrations • Substances will move across the cell membrane if their concentrations are unequal.

11. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Isotonic Solution Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

12. A cell in an isotonic solution 10% Solute 10% Solute Water moves in and out at the same rate How much solvent inside? How much solvent outside? 90% solvent 90% solvent Cell remains the same!

13. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Hypotonic Solution Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

14. A cell in a hypotonic solution 10% Solute 20% Solute Water moves in How much solvent inside? How much solvent outside? 80% solvent 90% solvent Cell swells!

15. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Hypertonic Solution Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) shrinks Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

16. A cell in an hypertonic solution 20% Solute 10% Solute Water moves out How much solvent inside? How much solvent outside? 90% solvent 80% solvent Cell shrinks!

17. What type of solution are these cells in? B C A Hypertonic Isotonic Hypotonic

18. Animations of Active Transport & Passive Transport Weeee!!! high low This is gonna be hard work!! high low Types of Cellular Transport • Passive Transport cell doesn’t use energy • Diffusion • Facilitated Diffusion • Osmosis • Active Transport cell does use energy • Protein Pumps • Endocytosis • Exocytosis

19. Passive Transport • cell uses no energy • molecules move randomly • Molecules spread out from an area of high concentration to an area of low concentration. (HighLow)

20. 3 Types of Passive Transport • Diffusion-diffusion of particles • Facilitative Diffusion – diffusion with the help of transport proteins • Osmosis – diffusion of water

21. Simple Diffusion Animation Passive Transport:1. Diffusion • Diffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low) • Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out.

22. Passive Transport: 2. Facilitated Diffusion A B 2. Facilitated diffusion: diffusion of specific particles with HELP from a transport proteins • Transport Proteins are specific – they “select” only certain molecules to cross the membrane • Transports larger or charged molecules (sugar) Facilitated diffusion(Channel Protein) Diffusion (Lipid Bilayer) Carrier Protein

23. Passive Transport: 2. Facilitated Diffusion Glucose molecules Cellular Transport From a- High High Concentration • Channel Proteins animations Cell Membrane Protein channel Low Concentration Low Transport Protein Through a  Go to Section:

24. Passive Transport: 3. Osmosis Osmosis animation • 3.Osmosis:diffusion of water through a selectively permeable membrane • Water moves from high to low concentrations • Water moves freely through pores. • Solute (green) to large to move across.

25. How Organisms Deal with Osmotic Pressure • Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure. • A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding. • Salt water fish pump salt out of their specialized gills so they do not dehydrate. • Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water. • Paramecium (protist) removing excess water video

26. Active Transport • cell uses energy (ATP) • actively moves molecules to where they are needed • Movement from an area of low concentration to an area of high concentration • (Low  High)

27. 3 Types of Active Transport • Protein Pumps-transport macromolecules across the cell membrane • Endocytosis-material ENTERING the cell • Exocytosis-material EXITING the cell

28. Sodium Potassium Pumps (Active Transport using proteins) Types of Active Transport • 1. Protein Pumps -transport proteins that require energy to do work • Example: Sodium / Potassium Pumps are important in nerve responses. Protein changes shape to move molecules: this requires energy!

29. Types of Active Transport • 2.Endocytosis: taking bulky material into a cell • Uses energy • Cell membrane in-folds around food particle Aka: “cell eating” • forms food vacuole & digests food (This is how white blood cells eat bacteria!)

30. 2 Types of Endocytosis… 1)Phagocytosis: large PARTICLES are engulfed 2) Pinocytosis: WATER drops are engulfed

31. Types of Active Transport Endocytosis & Exocytosis animations 3. Exocytosis:Forces material out of cell in bulk • membrane surrounding the material fuses with cell membrane • Cell changes shape – requires energy EX: Hormones or wastes released from cell

32. Passive Transport -Moves from HIGH to LOW 3 Types: 1) Diffusion-particles move fm H to L 2) Osmosis-water moves fm H to L 3) Facilitated Diffusion- particles move fm H to L with the HELP of transport protein REQUIRES NO ENERGY (ATP) Active Transport Moves from LOW to HIGH 3 Types: 1) Endocytosis- particles into the cell 2) Exocytosis- particles exists the cell 3) Protein Pump- particles moves with HELP of a transport protein with ATP REQUIRES ENERGY (ATP) Compare: Passive to Active Transport