Diffusion and Transport

1. Diffusion and Transport Ms. Klinkhachorn November 29, 2010 AP Biology

2. Announcements: • Quiz on THURSDAY • Organelles • Eukaryotes and Prokaryotes • Plant Cells and Animal Cells • Membranes • Passive Transport

3. Identify the Parts

4. Phospholipid Bilayer - Characteristics

5. Permeability of the Bilayer • Hydrophobic molecules can pass through, but hydrophilic molecules can not (at least not easily) • Polar molecules = hydrophilic • Examples: Sugars, charged atoms (K+) and molecules • Nonpolar molecules = hydrophobic • Examples: oxygen, carbon dioxide

6. Transport Proteins • Help materials that are big or hydrophilic pass through the membrane easily • Substance specific • If it’s supposed to translocate water and sugar, it will only translocate water and sugar • Two Kinds: • Channel Proteins • Carrier Proteins

7. Transport Proteins

8. Efficacy of Transport Proteins • 3 billion water molecules can move across the membrane using an aquaporin per second • Glucose moves across the membrane 50,000x faster with a transport protein than by itself

9. Passive Transport • Diffusion ACROSS A MEMBRANE • Diffusion = movement of molecules so that they spread out evenly in an available space • Does NOT require energy or use a transport protein • Once the molecules spread out they are in a state of equilibrium • Substances diffuse from a high concentration to a low concentration • They move down their own concentration gradient

10. Diffusion of Sugar

11. Concentration Gradient

12. Types of Passive Transport • Simple Diffusion • Facilitated Diffusion • Osmosis

13. Example: Gas Exchange

14. Simple Diffusion

15. Facilitated Diffusion • Diffusion that requires a transport protein

16. Osmosis • Diffusion of water across a selectively permeable membrane (where the solute cannot go through the membrane) • Water will move from an area of lower solute concentration to an area of higher solute concentration • Wants to balance out the solute concentrations

17. Osmosis

18. Hypertonic Solutions • “Hyper” means “above” • A hypertonic solution has a higher concentration of solute • This means that water is less concentrated • A cell placed in a hypertonic solution will SHRINK due to water loss.

19. Plant Cells in a Hypertonic Solution

20. Before and After

21. Hypotonic Solutions • “Hypo” means “below” • A hypotonic solution has a lower concentration of solute • This means that water is more concentrated • A cell placed in a hypotonic solution will SWELL due to water intake.

22. Isotonic Solutions • “Iso” means “equal” • An isotonic solution has an equal concentration of solute • A cell placed in an isotonic solution will remain unchanged • There will still be movement of water, though there is NO NET GAIN.

23. DNA – November 30, 2010 Answer these on the back of your study guide: • What is diffusion? How is it different from passive transport? • What do the word forms “hypo”, “hyper”, “osmo” and “iso” mean? • Describe what is happening in the picture.

24. Water Balance in Animal Cells • If the cell swells too much, it can burst. • This is called lysis. The cell lyses. • If the cell shrivels too much, it can die.

25. Examples (Animal Cell)

26. Water Balance in Plant Cells • Cells still swell in hypotonic environment, but the wall is more rigid. • Water uptake makes the cell turgid (firm). • This is a plant’s healthy state. • If the cell is in an isotonic environment, it is flaccid (limp) • If the cell is in a hypertonic environment, it plasmolyzes (a process called plasmolysis) • The cell membrane pulls away from the cell wall as water is lost • Can cause death.

27. Examples (Plant Cell)

28. Saltwater fish – Predict what happens to fish in these environments.

29. Saltwater Fish • Saltwater fish are constantly swimming in a hypertonic environment • Fish are consistently losing water from their bodies • In order to maintain water balance, the fish have to drink a lot of saltwater and pump salt out of their bodies

30. Freshwater fish – Predict what happens to fish in these environments.

31. Freshwater Fish • Freshwater fish live in a hypotonic environment • Water is constantly moving into their cells • These fish pee regularly in order to get rid of this water

32. Osmoregulation • Osmoregulation = the control of water balance • Certain organisms are adapted to deal with this • Sea animals • Paramecium

33. Paramecium • Paramecium lives in pond water, which is hypotonic to the cell. • What effect does the hypotonic environment have on this? • How might the paramecium adapt?

34. Contractile Vacuole

35. DNA – December 1, 2010 • Give an example of how organisms have adapted to deal with hypertonic or hypotonic living conditions. • Explain what a hypertonic and a hypotonic environment will do to a piece of celery.

36. Osmosis Practice

37. Active Transport • Active transport = movement of substances AGAINST their concentration gradient • Requires energy  ATP • Uses a transport protein, specifically a carrier protein • This allows cells to maintain certain solute concentrations

38. Sodium-Potassium Pump