1. Cell Transport

2. Structure of Cell Membrane The cell membrane is composed of a lipid bilayer. Because of its’ structure, it is selectively permeable, meaning it only allows certain substances in and out.

3. The lipids that make up the cell membrane are called phospholipids. POLAR HEAD NON-POLAR TAIL

4. OUTSIDE THE CELL Carbohydrate Chain Cytoskeleton filament Cytoplasm Protein channels Cholesterol

5. Homeostasis and the Cell Membrane  Every cell exists in some type of liquid environment, allowing materials to enter and leave.  The cell needs to maintain homeostasis, or a balance of materials inside itself as it reacts with its environment.  The way it does this is by having a selectively permeable membrane.

6. Selectively Permeable  It only allows certain things to enter and leave the cell  Ex. Water, carbon dioxide, and oxygen are all allowed through  Ex. Blood cells and organelles are not allowed to pass through the membrane

7. How Does Transport Work Through a Cell Membrane?

8. Passive Transport vs. Active Transport  Passive transport – transport of materials from a higher to lower concentration. Energy is not required for this to occur.  Active transport – transport of materials from a lower to higher concentration. Energy is needed for this to occur. high low Weeee!! ! high low This is gonna be hard work!!

9. Passive Transport 3 types of passive transport:  Diffusion - transport of substances  Facilitative Diffusion – transport with the help of carrier proteins (for molecules too large to pass through the membrane without help)  Osmosis – transport of water

10. Types of Diffusion

11. Diffusion Transport of substances (other than water) from areas of high to low concentration. Diffusion occurs until the molecules are distributed evenly throughout.

13. Diffusion Through Cell Membranes Molecules tend to diffuse across a cell membrane until equilibrium is reached (the same amount of solutes on both sides). For example: The capillary to the right is returning blood to the lungs. It has a high concentration of carbon dioxide. The air sacs in the lungs have a lower concentration of carbon dioxide. Which way will the carbon dioxide go? Capillary (bloodstream) CO2 air sacs

14. Facilitated Diffusion  Diffusion of molecules with the aid of carrier proteins, located in the cell membrane, from high to low concentration  Facilitated diffusion occurs for molecules such as glucose, ions, and proteins.

16. Osmosis  The diffusion of water across a selectively permeable membrane (high to low concentration)

17. Oops! What is he doing here?

18. Osmosis Across a Barrier

19. Notice the water rises on the left side of the tube, as water moves from right to left. The sugar concentration is higher on the left, so water moves through the membrane until the solutions are about equal in terms of sugar concentration

20. What causes water to act this way?

21. Answer: Osmotic Pressure This is the force exerted by osmosis that “pushes” water through the membrane to make the concentration of solutes the same on both sides

22. Types of Solutions or Environments for a Cell: 3 Situations for Osmosis…Which way will the water go?

23. Isotonic Solutions:   There is an equal concentration of water and solutes both in and outside the cell.   Water moves equally in both directions.   Ideally, this is the state a cell wants to be in.

24. Hypotonic Solutions:  The environment around the cell has a higher concentration of water than the cell.  Water moves into the cell.  The cell begins to swell, and may burst. This is called cytolysis.

25. Hypertonic Solutions:   The cell has a higher concentration of water than its surroundings.   Water moves out of the cell.   The cell begins to shrink, and may shrivel and die if it continues. This is called plasmolysis.

26. Hypertonic, Hypotonic, or Isotonic? A balloon has a higher salt concentration than its environment. Water diffuses into the balloon faster, swelling it until the salt concentrations in and out are equal.

27. Answer: HYPOTONIC Most freshwater fish have a special organ that pumps out the excess water as it rushes into their body. If they did not have some way to combat this, their cells will burst (cytolysis) and the fish would die.

28. Hypertonic, Hypotonic, or Isotonic? A balloon has a lower salt concentration than its environment. Water diffuses out of the balloon, shrinking it until the salt concentrations in and out are equal.

29. Answer: HYPERTONIC Fish living in the ocean must have a way to deal with the high salt environment of the ocean, or their cells would shrivel (plasmolysis) and the fish would die. Most ocean fish have high salt concentrations in their body to keep that from happening.

30. Hypertonic, Hypotonic, or Isotonic? A water-filled balloon has the same salt concentration as its environment. The water diffuses in and out at the same rate. The balloon, therefore, stays the same size.

31. Answer: ISOTONIC Jellyfish have a high salt concentration inside their body, equaling that of its salt water environment. If it did not have this trait, it would dry up (plasmolysis).

32. How do cells deal with the problem of osmotic pressure?

33. 1. Cells Are Surrounded by Blood:  Animal cells are bathed in blood.  Blood has a certain amount of proteins, sugars, salts, and other solutes that equal that of the cell.  Why aren’t your body cells surrounded by pure water?

35. Example 1:  When receiving an IV in a hospital, they are pumping fluids with certain concentrations of water, salts, proteins, etc. into your body.  Why do you think IV’s contain these substances, rather than pure water?  What type of environment would your cells be in, if the IV’s did contain pure water?

36. Answer:  Hypotonic

37. Example 2:  When you engage in physical activity, it is recommended that you drink water, rather than coke or other sugary drinks.  What could happen to your body if you do not drink water during physical activity on a hot day?  What type of environment are you creating for your cells?

38. Answer:  Hypertonic

39. 2. Plant Cells Have Turgor Pressure The cell walls of plants create turgor pressure. This is the amount of force exerted by their cell walls to help them keep their shape. High Turgor PressureLow Turgor Pressure

40. Is the turgor pressure high or low? What type of environment do you think these plant cells are in? Is the turgor pressure high or low? What type of environment do you think these plant cells are in?

41. Examples of Hypertonic, Isotonic, and Hypotonic Solutions in Plant Cells:

42. Is this plant in a hypertonic, hypotonic, and isotonic environment? Answer: Hypertonic Did the turgor pressure increase, decrease, or stay the same? Answer: decreased What happened to the plant, plasmolysis or cytolysis? Answer: plasmolysis

43. Is this plant in a hypertonic, hypotonic, and isotonic environment? Answer: Hypotonic Did the turgor pressure increase, decrease, or stay the same? Answer: increased What happened to the plant, plasmolysis or cytolysis? Answer: cytolysis

44. Is this plant in a hypertonic, hypotonic, and isotonic environment? Answer: isotonic Did the turgor pressure increase, decrease, or stay the same? Answer: stayed the same Which direction is the water moving? Answer: both directions

45. Think About It…  Plants wilt when turgor pressure (increases / decreases).  A wilted plant will regain its shape when turgor pressure (increases / decreases).  Plasmolysis occurs with (increased / decreased) turgor pressure.  Cytolysis occurs with (increased / decreased) turgor pressure.

46. 3. Some Cells Have Contractile Vacuoles Some organisms, such as the paramecium, have contractile vacuoles to pump out excess water.

47. Think About It…  (Cytolysis / plasmolysis) would occur if the paramecium did not pump out the excess water.  (Cytolysis / plasmolysis) would occur if the paramecium were placed in a salt water environment.

48. Active Transport Transport of substances from high to low concentrations. This requires energy.

49. Active Transport -There are two types: Endocytosis – takes materials into the cell (low to high concentration) Exocytosis – materials exit the cell (low to high concentration)

50. Types of Endocytosis Pinocytosis – for fluids Phagocytosis – for solids Using vessicles

51. Examples of Phagocytosis (Endocytosis) Macrophage (white blood cell) engulfing bacteria Amoeba engulfing food.