# Cell Membrane Lab Report

BioLab3

Cell Membranes

Lab Report

Student Name:

I. Diffusion

Define the following terms.

Solvent

Solute

Solution.

Diffusion

Concentration gradient

Dynamic equilibrium

EXERCISE 1 – Factors influencing rate of diffusion

Predict how molecule size and temperature will affect the outcome of this experiment.

Record the data from the information in the lab.

Potassium Permanganate R.T.

Methylene Blue R.T.

Time (min)

Total Diameter

(mm)

Distance of Diffusion * (mm)

Rate (mm/min) *

Total Diameter

(mm)

Distance of Diffusion * (mm)

Rate (mm/min) *

0

15

30

45

Potassium Permanganate 5 Celsius

Methylene Blue 5 Celsius

Time (min)

Total Diameter (mm)

Distance of Diffusion * (mm)

Rate (mm/min) *

Total Diameter

(mm)

Distance of Diffusion * (mm)

Rate (mm/min) *

0

15

30

45

* Distance diffused = diameter of each reading minus initial diameter Rate = distance in mm/elapsed time (min)

Double click the chart below. A spreadsheet will open. Enter the data from the table above into the spreadsheet in the areas provided. When you are finished, click into another area of the lab report. The spreadsheet will close automatically. Do not close the spreadsheet with the X in the upper right corner.

What effect did temperature have on the rate of diffusion?

How did molecule size affect the rate of diffusion?

What happens to the rate of diffusion over time? Why?

What can you conclude from this experiment?

II. Osmosis

Define the following terms.

Osmosis

EXERCISE 2 – Osmosis demonstration

After 15 minutes, record the volume change in each tube.

Osmometer

Dialysis Tube Contents

Beaker Contents

Volume Fluid Moved

Direction of Movement

1

2

Describe the net movement of water in osmometer 1.

Describe the net movement of the water in osmometer 2.

How is the movement of water molecules related to the concentration gradient of the water?

EXERCISE 3 – Effect of solute concentration on rate of osmosis

Subtract the beginning mass from the final mass for each of the five bags. Record the difference in the table below.

Double click the chart below to open a spreadsheet and enter the results from the table above to complete the graph. When you are finished with your work, click into another area in the lab report to close the spreadsheet (do not use the X in the upper right hand corner). For visual purposes the answer key shows the chart only from 10 grams to 22 grams. Your chart will begin at 0 grams.

Answer the questions below based on data displayed in the graph above.

Was the direction of net movement of water in bags 1 to 4 into or out of the bags?

Which bag gained the most weight? Why?

Explain the results from bags 4 and 5.

Viewing the data you entered in the table above, summarize the results for each bag. Summary

Tonicity of Bag/Beaker

1

2

3

4

5

III. Permeability of Membranes

EXERCISE 4 – Differential permeability

Tube 3 is tested for starch. Tube 4 is tested for chloride ions. Enter the data from the lab exercise into the table below.

Contents of Beaker

Contents of Bag

0 min

60 min

0 min

60 min

Starch

Chloride Ion

Which substances diffused through the dialysis membrane?

How does dialysis tubing model the differential permeability of a plasma membrane?

What physical property of dialysis tubing allows it to be differentially permeable?

IV. Tonicity

Define the following terms.

Tonicity

Hypotonic

Isotonic

Hypertonic

Turgid.

Plasmolysis.

Lysis

Lysed

Hemolysis

Hemolyzed

Crenation

A. Tonicity in Plant Cells

EXERCISE 5 – Plasmolysis in Elodea cells

Label which...

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