Biology 4A LaboratoryName:

Membrane Transport WorksheetLab Partner Names:

PART A – DIFFUSION OF A LIQUID INTO A SEMI-SOLID

Fill in Data Table 2 below with the class data: The Effects of Temperature on Diffusion Rates.

Time
(min) / Methylene Blue / Methyl Red / Methyl Violet / KMnO4
0˚C / 23˚C / 37˚C / 0˚C / 23˚C / 37˚C / 0˚C / 23˚C / 37˚C / 0˚C / 23˚C / 37˚C
0
30
  1. Which dye diffused more rapidly? Which dye diffused the slowest? Briefly explain why?
  1. Using Excel, graph the change in diffusion for each dye versus temperature on the same graph. Below this figure, type a short interpretation of the results from the graph and draw some conclusions.

PART B – OSMOSIS

Fill in Date Table 3: The Effects of Sugar Concentration on Osmotic Rate.

10% Solution / 60%% Solution
Time (min) / Mass (g) / Cumulative Mass Δ (g) / Mass (g) / Cumulative Mass Δ (g))
0 / ------/ ------
15
30
45
60
75
90
  1. Using Excel, create a figure of the cumulative mass changefor each sucrose solution against the time for both concentrations on the same graph.
  1. Where is the concentration of water higher, inside or outside the dialysis bag?
  1. Which bag gained water more rapidly? EXPLAIN why.

PART C – PLASMOLYSIS

  1. Photograph both normal and a plasmolyzed Elodea cells to show the difference in their respective appearances when viewed through the microscope and place them below.

Elodea cell (Normal)Elodea cells (Plasmolyzed)

  1. Using the principles of osmosis, account for the changes you observed when the Elodea cells were placed into the salt water environment.
  1. Explain why the cells did not burst when you placed deionized water on them.

PART D – ANIMAL CELL PERMEABILITY

Data Table 4: Results of the RBC permeability in hypotonic to hypertonic solutions and drawings.

Tube 1 / Tube 2 / Tube 3
Tonicity?
RBC Sketch
  1. Explain the results shown on Data Table 4. Which solution was: hypertonic, isotonic and hypotonic?

PART E – DIALYSIS THROUGH NON-LIVING MEMBRANES

Fill in Data Table 5: Results of the dialysis/osmosis experiment with an artificial membrane. Use (+) for the presence or (-) absence of a substance.

Outside Bag / Inside Bag
Substance / Before / After / Before / After
NaCl
Glucose
Protein
Starch
  1. Weight of the bag before:
  1. Weight of the bag after:
  1. Based upon your data from Data Table 5, which substances were able to pass through the membrane? Explain the direction of movement and why they were able to pass through the artificial membrane in Data Table 6 below.

Data Table 6. Summary for the dialysis experiment.

Did diffusion occur (Yes or No)? / Direction of movement (into or out of the bag) / Reason for movement or lack of movement?
NaCl
Glucose
Protein
Starch
  1. Cite the evidence whether osmosis occurred in this experiment.

PART F:WHY DON’T CELLS GROWTOO LARGE

Complete Data Table 7: The Effects of Cell Size and Diffusion of “Nutrients”

Cell / Colored Portion Before “Feeding” / Colored Portion After“UNFeed” / Percent of Cell “Fed”
SA / Volume / SA/V Ratio / SA / Volume / SA/V Ratio
1x1x1 cm
2x2x2 cm
3x3x3 cm

Percent of cell fed = vo – vu x 100Where:vo = volume of cell

vovu = volume of unfed portion

  1. What is the hypothesis that is being tested in this experiment?
  1. Discuss the relationship between cell size and SA/V ratio for eachcube.
  1. Which cube size had the most diffusion medium after 15 minutes – the largest, medium or the smallest?Carefully remove the “yellow” regions of the large and middle sized cube for comparison.
  1. After removing all the yellow “fed” portions, which cube size had the greatest extent of diffusion (least amount of yellow)?
  1. Explain which cell size and surface-area to volume ratio best meet the diffusion needs of living cells?
  1. Explain why prokaryotic cells are approximately ten times smaller than eukaryotic cells.

Biology 4A LabMembrane TransportPage 1 of 4