Biology 5090/32 — October/November 2021
Cambridge O-Level · Practical Test · worked solutions for every part, with the mark scheme
Topics Experimental Contexts · Observations and Measurements · Planning Experiments and Investigations · Use of Techniques, Apparatus and Materials · Analysis, Conclusions and Evaluation · Microscopy and Biological Drawing
Cells have membranes which can allow molecules to enter and leave the cell.
You are going to carry out an investigation into the movement of glucose and protein molecules through a membrane.
You are provided with:
- a piece of Visking tube that acts in a similar way to a cell membrane. It has a knot tied in one end to seal it. It has been soaked in distilled water to make it easier to handle.
- a large test-tube
- two solutions, A and B.
Use the following method:
- Half-fill the large test-tube with solution A.
- Take the Visking tube out of the distilled water.
- Hold the end of the tube without the knot and use your finger and thumb to rub it so that the tube opens. If you cannot open the end of the tube raise your hand for help to do this.
- Measure of solution B and add it to the inside of the Visking tube through the open end.
- Check that the contents are not leaking from the knotted end of the tube.
- Carefully rinse the outer surface of the Visking tube using distilled water and the container labelled waste water.
- Place the Visking tube into the large test-tube containing solution A so that it appears as shown in the diagram. The open end of the Visking tube should be folded over the top edge of the large test-tube.
- Check the levels of solution A in the large test-tube and solution B in the Visking tube. If solution A is below the level of solution B, add extra solution A to the large test-tube so that they are at the same level.
Record the time ______
- Leave this apparatus for 25–30 minutes.
Continue with questions (a)(i), (a)(ii) and 2 during this time.
You are provided with Benedict's solution to test for glucose and biuret reagent to test for protein.
Describe how you will carry out the tests for glucose and protein.
glucose
______
protein
______
Decide how you will label four test-tubes to use for testing solutions A and B for glucose and for protein.
- Label the test-tubes and record the labels in the table.
- Carry out the tests for glucose and protein on solutions A and B.
If you need hot water raise your hand when you require it. Caution: water will be hot.
Complete the table by recording your observations and conclusions.
| solution | test | test-tube label | observation | conclusion |
|---|---|---|---|---|
| A | glucose | |||
| protein | ||||
| B | glucose | |||
| protein |
- After 25–30 minutes remove the Visking tube from the large test-tube and place it in the waste water container.
Record the time and then calculate the total time that the Visking tube was in the large test-tube.
time that Visking tube was placed in large test-tube = ______
time that Visking tube was removed from large test-tube = ______
length of time Visking tube was immersed in solution A = ______
Test a sample of the solution from the large test-tube for glucose and another sample for protein. Raise your hand if more hot water is needed.
Record your observations and conclusions in the table.
| test | observation | conclusion |
|---|---|---|
| glucose | ||
| protein |
State two variables you should have controlled so that these repeat tests on solution A produced results that were comparable with those in the table in (a)(ii).
- ______
- ______
Describe and explain what the results of all the tests you have done show about the permeability of the Visking tube.
Suggest why it was important to rinse the outside of the Visking tube before placing it in the large test-tube containing solution A.
______
The rest of this paper
2 more questions- Q2Experimental Contexts · Observations and Measurements · Analysis, Conclusions and Evaluation · Planning Experiments and Investigations15M
- Q3Microscopy and Biological Drawing · Experimental Contexts7M