NOTES – Transport Through The Cell Membrane

1. NOTES – Transport Through The Cell Membrane

2. What is cell transport? • Cell Transport – when substances move into or out of cells • In order to get into or out of the cell, substances must pass through the cell membrane • Substances in a living thing naturally move from areas of high concentration (where there is a lot of that substance) to areas of low concentration (where there is less of that substance)

3. What are the 2 types of cell transport? • Passive Transport – When substances move in or out of cells from areas of high concentration to areas of low concentration

4. Passive Transport - Diffusion • Diffusion - the process by which molecules spread from areas of high concentration, to areas of low concentration(H L) • Dynamic Equilibrium - When molecules are evenly spread throughout a space

5. Passive Transport - Osmosis • Osmosis is the process by which WATER moves from areas of high concentration to areas of low concentration (H L)

6. Relationship between diffusion of solute molecules and osmosis • Diffusion and osmosis happen in opposite directions • Diffusion is the movement of solute • Osmosis is the movement of solvent (water) • Solutions that have relatively high concentrations of solute, have relatively low concentrations of solvent, and vice versa

7. Passive Transport EX. If there is a lot of sodium outside of a cell, the sodium moves into the cell by diffusion and water moves out of the cell by osmosis

8. Two Solutions Are Separated By A Selectively Permeable Membrane • Solution A has a high concentration of solute compared to solution B • Solution B has a high concentration of water compared to Solution A • So what happens?

9. Two Solutions Are Separated By A Selectively Permeable Membrane • Solute moves through the membrane from Solution A to Solution B (Diffusion) • Solution A becomes less concentrated, Solution B becomes more concentrated

10. Two Solutions Are Separated By A Selectively Permeable Membrane • Water moves through the membrane from Solution B to Solution A (Osmosis) • Solution B becomes more concentrated, Solution A becomes less concentrated

11. Two Solutions Are Separated By A Selectively Permeable Membrane • Dynamic equilibrium is reached • Solute and Water move back and forth equally

12. Rate of Diffusion • The rate (speed) of diffusion is influenced by 3 factors: • A. Temperature: As Temp. increases, the rate of diffusion also increases TD • B. Concentration: As the Conc. increases, the rate of diffusion also increases C D • C. Pressure: As the Pressure increases, the rate of diffusion DECREASESP D

13. Passive Transport - Facilitated Diffusion • Facilitated Diffusion - the movement of molecules from HL, through protein molecules in the cell membrane

14. The Rime of the Ancient MarinerBy Samuel Taylor Coleridge (written in 1797-98) • Water, water, every where, And all the boards did shrink; Water, water, every where, Nor any drop to drink.

15. Salt-Cured Meat • Meat or fish preserved or cured with salt • The only widely available method of preserving food until the 19th century • Salt prevents the growth of bacteria by drawing water out of bacteria cells by osmosis • Salted meat was a staple of the mariner's diet in the Age of Sail. It was stored in barrels, and often had to last for months spent out of sight of land.

16. What are the 2 types of cell transport? • Active Transport – When the cell uses energy to move substances in or out from an area of low concentration to an area of high concentration (L H)

17. Active Transport • The cell must USE ENERGY because substances do not naturally move from low concentration to high concentration • The cell must also use energy to move very large particles into or out of the cell

18. Bulk Transport • Bulk Transport - the movement of large amounts of material into or out of the cell • Endocytosis – movement into the cell • Exocytosis – movement out of the • Both processes occur when the material is too large to pass through the cell membrane

20. Two Types of Endocytosis • A. Phagocytosis = “cell eating” cell takes in large solid molecules • Ex: white blood cell engulfing a bacteria • B. Pinocytosis = “cell drinking” cell takes in large amount of fluid

21. Video Clip of Active Transport

22. Another way to look at it…

23. As the cell’s external environment changes, passive transport causes water and other substances to continuously move into and out of cells Turgor Pressure – pressure in a cell caused by water Plant cells need the correct amount of turgor pressure to stay rigid What are the effects of passive transport on cells?

24. Elodea Cells Before and After Placement in a Hypertonic Solution

25. What happens if there is a lower concentration of substances outside the cell?

26. What happens if there is a lower concentration of substances outside the cell?

27. What happens if there is a lower concentration of substances outside the cell? • Type of Solution Hypotonic • Turgor Pressure High • Cell Shape Swollen

28. Plant Cell - Hypotonic • Cell is turgid (rigid from high turgor pressure)

29. What happens if the concentration of substances outside of the cell is equal to the cytoplasm

30. What happens if the concentration of substances outside of the cell is equal to the cytoplasm

31. What happens if the concentration of substances outside of the cell is equal to the cytoplasm • Type of Solution Isotonic • Turgor Pressure Normal • Cell Shape Normal (Flaccid if plant)

32. Plant Cell - Isotonic • Cell is flaccid (turgor pressure not quite high enough to maintain rigidity)

33. What happens if there is a higher concentration of substances outside of the cell?

34. What happens if there is a higher concentration of substances outside of the cell?

35. What happens if there is a higher concentration of substances outside of the cell? • Type of Solution Hypertonic • Turgor Pressure Low • Cell Shape Shriveled

36. Plant Cell - Hypertonic • Cell is plasmolyzed (turgor pressure too low to hold membrane against cell wall)

37. Animal Cells in Different Solutions • Cytolysis – animal cell bursts in hypotonic solution • Crenation – when a cell shrinks in a hypertonic solution

38. Osmotic Effects on Cells

39. How do I figure out the direction of passive transport? • Look at the solution outside of the cell. Compared to the cytoplasm, is the concentration of substances higher, lower, or equal? • Diffusion – Which way will the substances move? (into cell, out of cell, in or out equally) • Osmosis – Which way will water move? (into cell, out of cell, in or out equally)

40. To sum up… • If there is a lot of substance outside a cell, substance moves in (diffusion), water moves out (osmosis) and the cell shrivels • If there is a lot of substance inside a cell, substance moves out (diffusion), water moves in (osmosis) and the cell swells • These processes happen naturally (passive transport), if the cell wants the opposite to happen, it must use energy (active transport)

41. Cells need a steady supply of energy for active transport otherwise they would not be able to adjust to their environment

42. Cell Transport Animations http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.swf