Biology 5090/32 — May/June 2010
Cambridge O-Level · Practical Test · worked solutions for every part, with the mark scheme
Topics Observations and Measurements · Experimental Contexts · Analysis, Conclusions and Evaluation · Use of Techniques, Apparatus and Materials · Planning Experiments and Investigations · Microscopy and Biological Drawing
Fruits of banana, Musa spp, change as they ripen.
You are provided with two pieces from an unripe banana fruit, labelled S1, and two pieces from a ripe banana fruit, labelled S2.
Describe the observable differences between one piece of S1 and one piece of S2.
______
- Using forceps, dip the cut surface of one piece of S1 and one piece of S2 into the iodine solution for approximately 3 seconds.
Describe and explain the observable differences between S1 and S2 after this test.
______
Describe a food test that you could carry out to show that the ripe banana S2 contains more reducing sugar than the unripe banana S1, including at least one safety factor.
______
- Cut the other pieces of S1 and S2 each into three equal parts.
- Test one of these pieces of S1 and one of these pieces of S2 for reducing sugar.
Complete the table below by recording your observations and conclusions.
| S1 | S2 | |
|---|---|---|
| observations | ||
| conclusions |
One of the changes that takes place as a banana fruit ripens is the breakdown of starch to sugar.
How do your results in (a)(ii) and (b)(ii) support this statement?
______
- Put one piece of S1 into an empty beaker and leave this open to the air. Label the beaker S1.
- Put the other piece of S1 into one of the beakers labelled S3, which contains a dilute acid. Label this beaker S1.
- Put one piece of S2 into an empty beaker and leave this open to the air. Label the beaker S2.
- Put the other piece of S2 into one of the beakers labelled S3, which contains a dilute acid. Label this beaker S2.
- Leave these for at least 15 minutes.
While waiting for 15 minutes, begin Question 2.
- Observe the appearance of the pieces of S1 and S2 that were left.
Complete the table below by describing the appearance of the two pieces of S1 and S2.
| exposed to the air | in S3 | |
|---|---|---|
| S1 | ||
| S2 |
Suggest what may have caused any differences in appearance between the pieces of banana left open to the air and those immersed in dilute acid.
______
Outline, but do not carry out, an investigation to find out the effect of pH on the changes you observed.
______
The rest of this paper
1 more questions- Q2Microscopy and Biological Drawing · Experimental Contexts · Observations and Measurements · Analysis, Conclusions and Evaluation17M