Reference no: EM133710118

Assignment: Cell Membrane Lab Report

A. Diffusion

I. Define the following terms.

Solvent
Solute
Solution
Diffusion
Concentration gradient
Dynamic equilibrium

II. In Lab Section I, Exercise 1, explore the factors influencing the rate of diffusion.

1. Record the data from information in the Lab in the table below.

Time (min)	Diameter (mm)
	5°C MB	5°C PP	23°C MB	23°C PP
0
15
30
45

B. Osmosis

I. In Lab, explore the effect of solute concentration on the rate of osmosis, then complete the following table and construct a graph.

1. Examine data presented in the lab and record the masses, then subtract the initial mass from the mass of each of the five bags at 20 minutes and 40 minutes to determine mass change.

No.	Bag contents/ beaker contents	0 min	20 min	40 min	60 min	Total Wt Gain
1	distilled H2O/ distilled H2O
2	10 % sucrose/ distilled H2O
3	20% sucrose/ distilled H2O
4	40% sucrose/ distilled H2O
5	distilled H2O/ 40% sucrose

2. Construct a line graph showing the mass change through time for the five bags. Include a legend, label both axes, and include units. Hint: you should have five lines on your graph with both positive and negative mass change values. Sign, date and prepare an image of your graph and include it with this lab report.

3. Analyze the data and explain how concentration gradient affected mass change in bags 4 and 5.

C. Permeability of Membranes

I. In Lab Section III, Exercise 4, learn about the importance of selectively permeable membranes, then complete the table and answer the following questions.

	Contents of Beaker		Contents of Bag
	0 min	60 min	0 min	60 min
Starch
Chloride Ion

II. Which substances diffused through the dialysis membrane?

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

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

D. Tonicity

I. In Lab Section IV, Exercise 5 and 6, observe plasmolysis in Elodea cells and tonicity in red blood cells. Summarize the concept of tonicity using blood and Elodea cells as examples. Your description should incorporate these terms: turgid, plasmolysis, hemolysis, and crenation.

Cells	Isotonic Solution	Hypertonic Solution	Hypotonic Solution
Elodea
RBC

II. Draw an illustration of an Elodea cell in each box. Include arrows to show the direction of water flow relative to each cell and dots to symbolize solutes. Sign, date and prepare an image of your drawing and include it with this lab report.

Solution	Elodea cell	Turgid or Plasmolyzed?
Water
Sucrose

Task

I. Compare diffusion and osmosis. Give an example of each.

II. In which direction will osmosis occur if a 15% sugar solution is separated from a 25% sugar solution by a differentially permeable membrane?

III. Why did osmosis, but not diffusion of sucrose molecules, occur across the dialysis membrane containing 20% sucrose solution?

IV. You are having a party and the celery has become limp. What might you do to make the celery crisp (turgid) again? What is occurring in the cells?

V. A small amount of fertilizer (mineral salts) will stimulate plant growth, but over fertilization can kill plants? Why?

VI. Michael adds sugar to his coffee. Explain what in this drink is the solvent, solute, and solution.

VII. You add a cube of sugar to your drink. How could you speed up the diffusion of sugar molecules without stirring?

VIII. How is dynamic equilibrium established within a solution?