Cellular Transport Lab

Due date: Monday, 11/16/15

Quiz Grade

Name:

Lab Objectives: from website

Hypothesis: what was your prediction from Tuesday?

Data Table 1:

Initial Mass (grams) / Final Mass (grams) / Mass Difference (grams) / Time in Beaker (minutes) / % Change in Mass
(see below)
Distilled Water
0.2 M
0.4 M
0.6 M
0.8 M
1.0  M

Percent change in mass = [(final mass-initial mass)/ initial mass] x 100

Graph 1: Show the relationship between % change in mass and the molarity of the solution. Include graph here.

Analysis Questions (for Exercise 1): Answer in FULL sentences please.

1.  Explain the relationship between the change in mass and the molarity of the sucrose within the dialysis bag.

2.  Was the distilled water in the “environments” hypertonic or hypotonic in relation to the sucrose solutions found in the “cells?”

3.  Predict what would happen to the mass of each bag in this experiment if all the bags were placed in 0.4 M sucrose solution instead of distilled water.

What would happen to the mass of the bag? / Why?
Distilled Water
0.2 M
0.4 M
0.6 M
0.8 M
1.0 M

4.  Why did you calculate the percent change in mass rather simply using the change in mass?

5.  Did your results match your predictions? List any sources of error that could have occurred that would cause your results to be askew.

Data Table 2:

Sample / Solution Color / % Change in Mass / Molarity / Type of Solution / Temperature
(K)
A
B
C
D
E
F

Graph 2: Show the relationship between % change in mass and the molarity of the solution. Include graph here.

Molar Concentration of Potato Slices = ______M

This would be the sucrose molarity in which the mass of the potato core does not change. To find this, draw the straight line on your graph that best fits your data. The point at which this line crosses the x-axis represents the molar concentration of sucrose with a water potential that is equal to the potato tissue water potential. At this concentration, there is no net gain or loss of water from the tissue.

Solute Potential (ψs) for the sucrose solution = ______bars

ψs = -iCRT

·  i = ionization constant (for sucrose, this is 1 because sucrose does NOT ionize in water

·  C = molar sucrose concentration at equilibrium (determined from your graph…the point at which your line (of best fit) crosses the x-axis.

·  R = pressure constant (0.0831 liter bar/mole °K)

·  T = temperature in Kelvins (273 + °C)

Analysis Questions (for Exercise 2): Answer in FULL sentences please.

1.  What does the molar concentration of the potato slices mean in regards to water loss or gain?

2.  If a potato slice is allowed to dehydrate in the open air, would the water potential of the potato cells decrease or increase? Why?

3.  Why is the ionization constant 1 for sucrose, but two for salt?

4.  If the water potential for a sucrose solution in a dialysis bag is -6.25 bars and it is immersed in a cup of sucrose solution having a water potential of -3.25 bars, and if the water potential inside and outside the bag is zero, will the bag gain or lose mass? Explain your answer.

5.  Fill in the blanks with all caps. Use the following words: exit, enter, osmotic, net gain, net loss, hypertonic, hypotonic, isotonic, high, low, less, more

If a cell is placed in a HYPERTONIC solution, the cell has ______solute in solution than the surrounding fluid and will therefore experience a ______of water to its surroundings. The cell has a ______water potential since there is a great deal of ______pressure causing water to leave the cell. Conversely, a cell sitting in a ______solution has a ______water potential, since it will experience a ______of water, there will be little osmotic pressure causing water to ______the cell.

6.  Fill in the following chart regarding the effects each type of solution has on cells.

Solution
Around Cell / Direction of Water / Effect on Animal Cells / Effect on Plant Cells

7.  Why can’t humans drink salt water for dehydration?