Osmosis & Diffusion, What you need to know: See also all your cell membrane, diffusion, and osmosis-related handouts 1. Diffusion: definition, passive, net direction of movement, factors that affect its rate (molecular mass, steepness of concentration gradient, temperature) 2. Calculate the surface area, volume, and surface area to volume ratio of cubes, rectangular solids, and spheres 3. Discuss how cell size and shape influence the efficiency of diffusion 4. Discuss how ionic an polar solutes affect water (being a polar molecule) and thus the [free water] 5. Correctly apply the comparative terms of: hypertonic, isotonic, hypotonic 6. Discuss the effects on plant and animals cells of being in each of these solutions 7. Calculate % change in mass and use this to rank solutions by concentration 8. Given a graph of % change in mass versus molarity, interpolate to determine the molarity of solution that potato tissue would be isotonic to 9. Discuss patterns in the direction of water movement in terms of: [solute], [free water], and water potential 10. Calculate water potential (given solute and pressure potential) 11. Given a dialysis bag/beaker solution scenario, infer which substances the dialysis tubing is permeable and impermeable to 12. Interpret graphs of % change in mass (of model cells made of dialysis tubing) to rank the molarities of solutions they contain 13. Discuss the role of protein channels called aquaporins in the diffusion of water across cell membranes State whether the solutions shown below are hypertonic, hypotonic, or isotonic relative to the cell: State whether the solutions shown below are hypertonic, hypotonic, or isotonic relative to the cell: What will be the net direction of water movement and explain why: What will be the net direction of water movement and explain why: Water will diffuse out of the model cell and into the beaker because: a. Water moves from an area of lower [solute] in the cell to a higher [solute] in the beaker b. Water moves from an area of higher [free water] in the cell to lower [free water] in the beaker 1. How do you calculate water potential? 2. What is the relationship between molarity and solute potential? 3. What is pressure potential? 1. 2. 3. How do you calculate water potential? Add solute and pressure potentials What is the relationship between molarity and solute potential? The higher the molarity [solute]) the lower (more negative) the solute potential becomes. What is pressure potential? It is due to the cell wall pushing back to appose the inward push of water in the plant cell (this is why plant cells do not burst like animal cells do when in a hypotonic solution). Cubes of agar with a pink pH indicator are placed into vinegar solution. The cubes will turn clear as vinegar diffuses into the agar. 1. Which of the cubes above will experience a complete color-change first ? 2. Explain your selection: Cubes of agar with a pink pH indicator are placed into vinegar solution. The cubes will turn clear as vinegar diffuses into the agar. Which of the cubes above will experience a complete color-change first ? The smallest cube Explain your selection: The smallest cube would have the largest S.A.:V. and have the shortest distance to the center and thus would be most efficient at diffusion Verbally describe the cell shape that can dramatically ↑ surface area to volume ratio, thus making diffusion more efficient Other than becoming smaller, how else can cells increase their surface area to volume ratio? Long, skinny cells like root hairs or villi/microvilli increase surface are to volume ratio 1. Which type of solution is best for our red blood cells? 2. What type of solution is IV fluid and why? 1. Which type of solution is best for our red blood cells? Isotonic 2. What type of solution is IV fluid and why? Isotonic – the red blood cells will neither swell (and perhaps burst) nor shrivel up 1. What would happen if red blood cells were placed in distilled water? 2. Explain why this would happen (include the correct use of hypertonic and hypotonic) in your explanation: 1. What would happen if red blood cells were placed in distilled water? Water would diffuse into the cell, the cell would swell, perhaps burst (lyse) 2. Explain why this would happen (include the correct use of hypertonic and hypotonic) in your explanation: The cell would be hypertonic to the distilled water, which is hypotonic, thus water would move from a higher [free water] in the solution and into the cell. A B C E F D 1. Which figure depicts an animal cell placed in a hypotonic solution? 2. Which two figures show a cell that is hypertonic to its environment? A B C E F D 1. Which figure depicts an animal cell placed in a hypotonic solution? A 2. Which two figures show a cell that is hypertonic to its environment? A and D H2O Mass of bag = 12.1 g Starch Glucose Mass of bag = 12.8 g 1. Verbally discuss which substance(s) (H2O, starch, and/or glucose) is the membrane permeable to? 2. Verbally discuss what your evidence is? H2O Starch Glucose 1. Which substance(s) (H2O, starch, and/or glucose) is the membrane permeable to? H2O and glucose 2. What is your evidence? There was a net increase in mass due to the influx of water, red dots in beaker indicate glucose has diffused out of the bag H2O Starch Glucose 1. Verbally discuss which substance(s) (H2O, starch, and/or glucose) is the membrane impermeable to? 2. Verbally discuss what your evidence is? H2O Starch Glucose 1. Which substance(s) (H2O, starch, and/or glucose) is the membrane imermeable to? Starch 2. What is your evidence? Equal number of blue dots inside the bag at start and end, no blue dots in beaker at the end H2O Starch Glucose 1. In the case of the dialysis membrane, what determines whether a substance can pass through? Based on pore-size of membrane, if smaller than pore-size, substances can pass, if larger than poresize, substances are blocked Create a graph that shows the amount of the following in the bag over the course of the investigation: starch, glucose, water Amount in Dialysis Bag Water would increase as it diffused into the bag Starch would stay the same (it can not leave the bag) Glucose would decrease as it diffused out of the bag Time (min.) Five dialysis bags are filled with various concentrations of sucrose. The bag is impermeable to sucrose. All bags were placed in a 0.4 M sucrose solution. 1. Which line(s) represents the bag whose contents were isotonic to the outside solution? 2. Which line(s) represent the bag whose contents were hypotonic to the outside solution? 3. Rank the bags from the lowest concentration to the highest initial internal sucrose concentration: Five dialysis bags are filled with various concentrations of sucrose. The bag is impermeable to sucrose. All bags were placed in a 0.4 M sucrose solution. 1. Which line(s) represents the bag whose contents were isotonic to the outside solution? C 2. Which line(s) represent the bag whose contents were hypotonic to the outside solution? D, E 3. Rank the bags from the lowest concentration to the highest initial internal sucrose concentration: E,D,C,B,A Surface area of a sphere = A = 4𝜋𝑟2 How many times larger is the surface area of a cell with a radius of 0.1 cm than a cell with a radius of 0.01 cm? Surface area of a sphere = A = 4𝜋𝑟2 How many times larger is the surface area of a cell with a radius of 0.1 cm than a cell with a radius of 0.01 cm? 4(𝝅)(0.01)2 = 0.001256 4(𝝅)(1)2 = 12.56 12.56/0.001256 = 10,000 With storm-surges, sea water is encroaching further inland. Use the concept of water potential in your answer: 1. Describe how the saltwater would affect the movement of water into or out of the plant 2. Explain how this would affect crop production With storm-surges, sea water is encroaching further inland. Use the concept of water potential in your answer: 1. Describe how the saltwater would affect the movement of water into or out of the plant Salt is a solute, thus when added to water it decreases the water potential. Since water moves from an area of higher towards lower water potential, water will leave the plant cells into the seawater solution. 2. Explain how this would affect crop production Plant cells would become flaccid (wilt) and the cell membrane might pull away from the cell wall (plasmalysis) resulting in cell death. Crop production would be reduced. What affect does the steepness of a concentration gradient have on the rate of diffusion? What would a graph of this relationship look like? What is the net direction of water movement in terms of water potential? Water moves from an area of higher to an area of lower water potential What is an advantage that Eukaryotic cells gain from having organelles (such as mitochondria)? What is an advantage that Eukaryotic cells gain from having organelles (such as mitochondria)? Processes can be compartmentalized. This increases metabolic efficiency. For example, incompatible processes can occur simultaneously in the same cell because they are separated in different “compartments”. The digestive enzymes within a lysosome can break down an old, defective protein, at the same time a new protein is being assembled on the ribosome of the rough endoplasmic reticulum.
