Membrane Transport – Cell Homeostasis

The purpose of the lab is to simulate what happens in a cell when placed into different environments. You will learn about osmosis, a special type of passive transport, which involves the movement of water from an area of higher concentration of solutes to an area of lower concentration of solutes without the expenditure of cellular energy.

Please refer to the chapter in your text on membrane transport and cells. You will need to know the different types of transport into and out of cellular membranes.

In this lab, you will work through a simulation that involves virtually preparing different sugar solutions and dialysis tubing containing different solutions. Please go the following website to access the lab: Cell Homeostasis Virtual Lab ( https://video.esc4.net/video/assets/Science/Biology/Gateway%20Resources/cell%20homeostasis%20virtual%20lab%20-%20activity/index.html )

Warning: If you click on the “back button” on your browser, your lab will start over at the beginning!!! So pay attention to each step as you are doing it. Once you reach the end, you do NOT have to start again.

Laboratory Outline:

In this lab, you will do the following:

· Prepare different sugar concentrations using weight to weight dilutions

· Observe the effects of different concentrations of sugar in a beaker to represent the environment as compared to different concentrations of sugar in dialysis tubing to represent the cell

· Create a graph of the data and provide a screenshot of the graph

· Answer questions pertaining to these activities and the concept of osmosis and diffusion

You will complete the following questions as you progress through the lab components. Some questions will require a screen shot of the image after you have achieved locating it at the proper magnification. Please “google” your computer for specifics on performing a screen shot. Some computers use “FN” and “PrntScm,” while others use “Ctrl” and “PrtScr” then pasting into your document.

You will need to create a bar graph for this lab. If you know how to do this in excel (or similar program) please use that application and insert into this worksheet where appropriate. IF you do not, go to the following website to assist you in making a basic bar graph: Here is a very basic graph program . ( https://nces.ed.gov/nceskids/createagraph/ )

The graphing website is simplified but will give the desired results. After you create the graph, perform a print screen to add it to this worksheet for question 7.

Answer each question in another color font (do not highlight your answers). Save your document as a .doc or .docx file and upload into ecampus for grading.

Questions:

1. Explain how to make a 5% sugar solution.

2. Explain how to make a 10% sugar solution.

3. Explain how to make a 15% sugar solution.

4. Label each of contents of the 5 beakers:

A:

B:

C:

D:

E:

5. Label the contents of each of the 5 dialysis tubes:

A:

B:

C:

D:

E:

6. Calculate the difference in the initial and final masses of each of the dialysis tubes (label with grams).

A:

B:

C:

D:

E:

7. Create a bar graph showing the initial mass and final mass for each dialysis tubes. Paste that graph here (screenshot or insert excel graph). The “y” axis should indicate mass in grams, the “x” axis the tubes, label the first group “initial” and the second group “final,” and be sure the exact measurement is shown at the top of each bar.

8. Which dialysis tubes had little or no change in mass after 24 hours? Why didn’t the mass of these tubes change?

9. Why is pure water used as a control group?

10. How do you know that osmosis was the transport that took place in this lab? Describe the process and why (utilize concepts from the lecture notes/book).

 

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