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2 water potential in potato cells was determined in

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Unformatted text preview: 2) Water potential in potato cells was determined in the following manner. The initial masses of six groups of potato cores were measured. The potato cores were placed in sucrose solutions of various molarities. The masses of the cores were measured again after 24 hours. Percent changes in mass were calculated. The results are shown below. Molarity of Sucrose in Beaker Percent Change in Mass 0.0 M 18.0 0.2 5.0 0.4 -8.0 0.6 -16.0 0.8 -23.5 1.0 -24.0 Graph these data to the right of the table. From your graph, label where the cells were hypotonic and the solution was hypertonic, and vice versa. Determine the apparent molar concentration (osmolarity) of the potato core cells. Osmolarity = ~0.275M cell and solution are isotonic Above ~0.275M cells are hypotonic while the solution is hypertonic (as cells are gaining mass = water is moving in) Under ~0.275M cells are hypertonic and the solution is hypotonic (as cells are losing mass = water is moving out) Looking at the water potential equation, When Solute potential goes down (gets more negative), water potential DECREASES When Pressure potential goes down (gets smaller), water potential DECREASES When would the pressure in a cell rise? (Under what conditions?) Why can only walled cells such as bacteria, fungi and plant cells generate turgor pressure, whereas animal cells cannot? When a cell is in a hypotonic environment, where water is entering the cell (hence building up pressure). The cell wall is strong and is able to hold pressure, whereas the plasma membrane alone would burst due to its inability to hold pressure. What would happen to the solute potential when the molar concentration of the solute is increased (justify with equation)? WHY? When Concentration is INCREASED Solute potential would go DOWN. iCRT (when C is increased, that is a bigger multiplier to the negative equation) What would happen to the solute potential when Temperature is increased (justify with equation)? WHY? When Temperature is INCREASED Solute potential would go DOWN. iCRT (when T is increased, that is a bigger multiplier to the negative equation) What would happen to the solute potential when the dissolved substance is glucose vs. NaCl (justify with equation)? WHY? When Ionization constant is INCREASED Solute potential would go DOWN. iCRT (when i is increased, that is a bigger multiplier to the negative equation) NaCl (i=2) glucose (i=1) since NaCl forms two ions when placed in water so its constant is 2 and glucose doesnt ionize so its constant is 1 Why is water potential important for plants? Allows for the movement of materials through the organism. Drives water up the plant through xylem by transpiration and cohesion-tension theory. Also builds up pressure for translocation of sugar through phloem. While plants have a vascular system, they lack the muscular pump (heart) to move materials and create pressure for them....
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2 Water potential in potato cells was determined in the...

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