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(a) (i) Describe how you will obtain accurate results to record the cells at different states of plasmolysis.
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[1]
(ii) Prepare the space below for recording your results.
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9. Record your results for S1 as you have described in (a)(i).
10. Repeat steps 1 to 9 with S2, S3 and S4.
(iii) Use your results to complete the following statement.
The sodium chloride concentration of the unknown sample, S4, is between
......................................... mol dm−3 and ......................................... mol dm−3.
[1]
(iv) Identify one significant source of error in using Fig. 1.1 to obtain your results.
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(v) Suggest how you would make three improvements to this investigation.
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[3]
(b) (i) Plot a graph of the data shown in Table 1.1.
concentration of sodium chloride / $\times 10^{-2}$ mol dm−3 percentage of red blood cells destroyed
5.5 100
6.0 96
6.5 74
7.0 31
7.5 10
8.0 0
[4]
(ii) State the sodium chloride concentration at which 50% of the red blood cells are destroyed.
Show on the graph how you obtained the concentration.
Sodium chloride concentration ...............................................................
[1]
(iii) Explain what is happening between the red blood cells and the external solutions when 0 and 100% of red blood cells are destroyed.
0% red blood cells destroyed
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100% red blood cells destroyed
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1. (a) (i) Complete Fig. 2.2 to show your observations. Label and annotate P and Q in Fig. 2.2 to describe your observations. [1]
6. Hold the syringe, labelled Y, in the test-tube, labelled Q, so that you can release one drop close to the surface of the oil.
7. Observe the contents of Q.
(ii) Complete Fig. 2.3 to show your observations. Label and annotate Q in Fig. 2.3 to describe your observations. [3]
8. As shown in Fig. 2.4 put a bung in the test-tube labelled Q. Shake the test-tube vigorously to mix the oil and water thoroughly so that the egg yolk is broken up.
9. As shown in Fig. 2.4 put a bung in the test-tube labelled P. Shake the test-tube vigorously to mix the oil and water.
10. After two minutes, observe the contents of P and Q.
(iii) Complete Fig. 2.5 to show your observations. Label and annotate P and Q in Fig. 2.5 to describe your observations. [2]
(b) (i) Make a large drawing of three different types of blood cell. Mark on the photomicrograph the cells that you have drawn. [4]
(ii) Prepare the space below so that it is suitable for you to show the observable differences between the red blood cells and the white blood cells shown in Fig. 2.6. Record your observations in the space you have prepared. [5]
(iii) Use the magnification to calculate the mean actual diameter, in \( \mu \text{m} \), of a crenated red blood cell using the labelled cells in Fig. 2.7. Draw the red blood cell, labelled J, and show where you measured this cell. You may lose marks if you do not show your working or if you do not use appropriate units. ....................................................... \( \mu \text{m} \) [6]
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