Biology 5090/31 — May/June 2011
Cambridge O-Level · Practical Test · worked solutions for every part, with the mark scheme
Topics Experimental Contexts · Observations and Measurements · Analysis, Conclusions and Evaluation · Planning Experiments and Investigations · Microscopy and Biological Drawing
Do not taste the fruit sections provided.
Describe how you would carry out a test for reducing sugars using Benedict's solution and the results you would expect if reducing sugars were present.
You are provided with a solution labelled S1.
Carry out the test you have described on a sample of S1 and record what you conclude about the solution.
You are provided with some potato tissue covered in polythene.
- Remove the polythene.
- Cut the potato tissue into small pieces and place these in a clean test-tube.
- Add some distilled water and shake the test-tube.
Carry out the test you described in (a)(i) on this mixture.
State your result and conclusion.
result = ______
conclusion = ______
You are provided with three dishes, each containing a similar piece of potato and a solution.
Each potato strip was cut exactly in length before being placed in the solution at least an hour before the start of the examination.
Dish A – contains S1 solution.
Dish B – contains half S1 and half distilled water.
Dish C – contains distilled water.
- Remove the potato strip from dish A.
- Blot the strip carefully on a paper towel.
Accurately measure the longest length of this potato strip and record the length in Table 1.1.
- Repeat the procedure with the potato strips in dishes B and C and record their lengths in Table 1.1.
Calculate the change in length between the initial and your measured length and complete Table 1.1.
Table 1.1
| length of potato strip / | |||
|---|---|---|---|
| A | B | C | |
| initial length | 5.0 | 5.0 | 5.0 |
| measured length | |||
| change in length |
Describe and explain the changes in length.
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