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AP BIO STUDY QUESTIONS UNIT II CELLS AND MEMBRANES OSMOSIS 1. How does the method of salt or sugar curing(a process in which meat is packed in salt or sugar) help to preserve the meat? After the third Punic War the Romans threw salt on the farmland around Carthage. What was the biological consequence of this action? Explain. A plant cell, when initially placed in pure water, has an osmotic potential of -4 bars and a pressure potential of +2 bars. a. Which way will water diffuse? b. When will net diffusion stop? c. When equilibrium is reached, what are the cell's osmotic potential and pressure potential values? A protozoan is placed in a 0.5 M sucrose solution at 27°C. Assume the cell has an initial osmotic potential of -2 bars. Because it lacks a cell wall, it cannot generate a turgor pressure and will always have a pressure potential of 0. a. When the cell is placed in a sucrose solution, which way will water diffuse? b. When will net diffusion stop? c. What will be the appearance of the cell when equilibrium is reached? d. What will be the cell's osmotic potential and pressure potential values at equilibrium?

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A dialysis bag is attached to the end of a glass tube to make a simple device called an osmometer. The dialysis tube contains a 1 M solution with a water potential of -35 bars. Since the osmometer is open to the air, pressure potential is initially 0 (but will increase as fluid moves up the tube). If the osmometer is placed in a beaker of water and osmosis occurs, what will be the water, osmotic and pressure potentials be at equilibrium for the solution in the bag and the water in the beaker?

Water Potential BAG BEAKER

Pressure Potential

Osmotic Potential

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Use the diagram at right, the equation s = -icRT, and your knowledge of water potential calculate the osmotic and pressure potentials of each solution at equilibrium. Temperature = 27o C.

Distilled Water

EXPERIMENT #1

Flacid dialysis bag 0.3 M Glucose Beaker

ADDITIONAL PRACTICE PROBLEMS (optional)

1. Use the following diagram, the equation s = -icRT, and your knowledge of water potential calculate the osmotic and pressure potentials of each solution at equilibrium. Temperature = 27o C.

0.12 M glucose Flacid dialysis bag 0.3 M Glucose Beaker EXPERIMENT #2

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A plant cell with a pressure potential of 5 bars and an osmotic potential of -9 bars is in equilibrium with a surrounding solution which is open to the air. What is the water potential of the surrounding solution? A plant cell with a pressure potential of 6 bars and an osmotic potential of -11 bars is placed in a beaker containing a sucrose solution with a water potential of -10 bars. What will be the final pressure and osmotic potentials in the cell after it has been allowed to reach equilibrium with the sucrose solution? A plant cell with a pressure potential of 6 bars and an osmotic potential of -11 bars is placed in a beaker containing distilled water. What will be the final pressure and osmotic potentials in the cell after it has been allowed to reach equilibrium with the water?

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MEMBRANES 1. What limits the passage of water and other polar molecules and ions through the cell membrane? How do such molecules get into and out of the cell? Describe three possible routes. For each diagram below, draw in and label the appropriate molecules which you would expect to find in each type of membrane. (Cell wall, cell membrane, integral & peripheral proteins, phospholipids, cholesterol, glycoproteins, glycolipids) ANIMAL CELL PLANT CELL

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cell exterior

cell interior

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In the diagram below showing the boundaries of the cell membrane, draw and label an active transport pump (Na+/K+ pump or proton pump) and an associated cotransport system for bringing glucose into a cell. Use arrows to show molecular movements and ion symbols to show relative concentration gradients.

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