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(a) (i) Complete Fig. 1.1 to show how you will make two further concentrations of copper sulfate solution. [3]
Proceed as follows:
1. Prepare the concentrations of copper sulfate solution as shown in Fig. 1.1 in the containers provided. Use the syringe labelled 'For copper sulfate'.
2. Label test-tubes with the concentrations of copper sulfate solutions and label another test-tube W.
3. Wipe the tile clean with a damp paper towel and then dry the tile. Label the tile, as shown in Fig. 1.2. The numbers indicate the sampling times in seconds.
4. Put one drop of iodine on the tile at each sampling time, as shown in Fig. 1.2.
5. Put 1 cm³ of W into the labelled test-tube.
6. Put 3 cm³ of S into the same test-tube. Mix well.
7. Put 0.5 cm³ of E into the same test-tube. Mix and start timing.
8. Use a glass rod to stir the mixture.
9. After 15 seconds use the glass rod to transfer a drop of the mixture to the iodine drop, labelled 15, on the tile.
10. Immediately clean the glass rod with a paper towel.
11. Repeat steps 8 to 10 at 15 second intervals until the iodine drop does not change colour. If the iodine drop changes colour at 180 seconds, record 'more than 180' as your result (for step 12).
12. Record the time taken to reach the end-point.
13. Repeat steps 3 to 12 replacing the 1 cm³ of W with 1 cm³ of the lowest concentration of copper sulfate solution.
14. Repeat step 13 with the other concentrations of copper sulfate solution.
(ii) Prepare the space below and record your results. [5]
(iii) The student's hypothesis stated that 'concentrations of copper sulfate solution below 0.03% will continue to inhibit the enzyme'.
Explain how your results provide evidence for the support or the rejection of this hypothesis. [2]
(iv) Identify one significant source of error in your investigation. [1]
(v) A colorimeter could have been used to determine the end-point. Describe three other modifications to this investigation which would improve the confidence in your results. [3]
(b) (i) Draw a circle around each of the anomalous results and complete the table. [2]
Table 1.1 shows the results of an investigation into the effect of the concentration of copper sulfate solution on a protein suspension. A protein suspension was mixed with different concentrations of copper sulfate solution. After a set time, the percentage absorbance of light was measured using a colorimeter.
(ii) Plot a graph of the data shown in Table 1.1. [4]
(iii) Explain the effect of copper sulfate solution on the protein suspension. [2]
504
504
600
J1 is a slide of a stained transverse section through a leaf.
[Image_1: Fig. 2.1]
(a) Draw a large plan diagram of the part of the leaf indicated by the shaded area in Fig. 2.1.
Label the xylem and an air space. [5]
(b) Make a large drawing of six cells from the part of the leaf indicated by the shaded area in Fig. 2.2.
The cells should be two adjacent (touching) cells from the epidermis and two adjacent cells from each of the next two layers.
[Image_2: Fig. 2.2]
Label one epidermal cell. [5]
(c) Fig. 2.3 is a photomicrograph of a transverse section through a leaf of a different plant species.
[Image_3: Fig. 2.3]
The actual length of line Y is 785 μm.
Use this measurement to calculate the magnification of Fig. 2.3.
You may lose marks if you do not show your working or if you do not use appropriate units.
magnification · .................................................. [3]
(d) Prepare the space below so that it is suitable for you to record the observable differences between the specimens on J1 and in Fig. 2.3.
Record your observations in the space you have prepared. [5]
594
585
523
