AS & A Level Biology - 9700 Paper 3 2013 Summer Zone 2

Yeast cells use enzymes as part of their metabolic reactions. Some of these reactions release oxygen from hydrogen peroxide solution.
You are required to investigate the effect of temperature (independent variable) on the release of oxygen from hydrogen peroxide solution.
You are provided with:

[Table_1]

Proceed as follows:
You are required to change the temperature of Y during the investigation.

1. Put the beaker containing Y into a large beaker (W) which will be the water-bath as shown in Fig. 1.1.



(a) (i) Decide what level of water you will start with in W.
Show on Fig. 1.1 the level of water in W. [1]

2. Put hot water from the beaker provided into W to below the level you decided.
Add hot water and cold water as needed to obtain a water-bath of between 40°C and 45°C. Adjust the volume of water to the level you decided in (a)(i). The beaker may float but should not spill its contents.

3. Keep Y (in W) at a temperature between 40°C to 45°C.
Fig. 1.2 shows the apparatus set up to measure the release of oxygen from hydrogen peroxide solution. The oxygen released into B can be measured (dependent variable) by counting the number of bubbles.



The end of the delivery tube should be 1 cm below the level of the water in test-tube B as shown in Fig. 1.2.
(ii) Decide how you will standardise the position of the delivery tube in test-tube B as shown in Fig. 1.2.
Describe how you standardised the position of the tube. [1]
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4. Put water from the beaker or container, labelled cold, into test-tube B as shown in Fig. 1.2.
5. Remove the small beaker or container containing Y from W.
6. Record the temperature of Y. .............................................

7. Stir Y and put 1 cm³ into the large test-tube A. Put the beaker containing Y back into W.
The reaction will start as soon as you add H (in step 8).
You are required to count the number of bubbles released into B by making a small mark on Grid 1.1 for each bubble as it is released for the intervals shown below.
If the number of bubbles is too many to record for any one time, record 'too many' for that interval.

Example:



Grid 1.1 – for recording higher temperature



8. Put 4 cm³ of H into the large test-tube A, immediately put in the bung and start timing and recording.
9. After 4 minutes, remove the bung from test-tube A.
You are provided with a container labelled 'for waste' and a container labelled 'for washing' so you can re-use the large test-tube A.

10. Decide on a lower temperature for your next investigation.
Adjust the temperature of W and put the beaker containing Y into W for 5 minutes.
After this 5 minutes, record the temperature of Y ..................................................

11. Repeat steps 7 to 9.
Use Grid 1.2 to record your readings.

Grid 1.2 – for recording lower temperature



(iii) Prepare the space below and record your results. [6]

(iv) Identify two significant sources of error in your investigation. [2]
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(v) Describe three modifications to this investigation which would improve the confidence in your results. [3]
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In a similar investigation, some scientists investigated the effect of the concentration of hydrogen peroxide on the release of oxygen from hydrogen peroxide solution, using yeast as a source of enzymes. The breakdown of hydrogen peroxide solution was measured by the time taken to collect 20 cm³ of oxygen.
The results are shown in Table 1.1.

[Table_2]

(b) (i) Two of the values in Table 1.1 are anomalous.
Draw a circle around each of these values. [1]

(ii) Complete Table 1.1 by calculating the missing value. [1]

(iii) Plot a graph of the data shown in Table 1.1. [4]



(iv) Using the data in Table 1.1 and your graph, explain the results for the investigation. [2]
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(a) (i) Draw a large plan diagram of the part of the stem indicated by the shaded sector in Fig. 2.1.
On your diagram, use a ruled label line to show the pith.

Fig. 2.1

(ii) The cells in each corner of the stem are different from the cells in the centre of the stem.
Make a large drawing of one group of three whole, adjacent (touching) cells
• from the tissue in one corner, as observed on the specimen on M1.
Make a large drawing of one group of three whole, adjacent (touching) cells
• from the tissue in the centre of the stem, as observed on the specimen on M1.
On your drawing, use a ruled label line and label to show one cell wall.
cells from the tissue in one corner
cells from the tissue in the centre of the stem

(iii) Use the eyepiece graticule scale to find the mean width of the:
• cells in the centre of the stem
• cells in a corner of the stem.
State the ratio of the mean width of the cells in the centre of the stem to the mean width of the cells in a corner.

Note: You are not required to calibrate the eyepiece graticule scale with a stage micrometer.

You will lose marks if you do not show all the steps in finding the ratio.

(iv) The cells in the corner of the stem on M1 carry out the function of support.
Suggest one observable feature which supports this conclusion.
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(b) Prepare the space below so that it is suitable for you to record observable differences between the specimens on slide M1 and in Fig. 2.2 to include:
• the vascular tissue
• at least two other tissues.

Fig. 2.2