20 7 A student investigated the effect of the concentration of sodium chloride solution on blood. The student set up six test tubes, each with a different concentration of sodium chloride solution. Five drops of blood were added to each test tube. The appearance of the solutions was then recorded. Samples of each solution were observed using a light microscope. The table shows the results of this investigation. Concentration of sodium chloride (%) Appearance of solution after blood was added Observation with light microscope 3.0 very cloudy cells seen with shrunken edges 1.0 very cloudy cells seen 0.9 very cloudy cells seen 0.7 slightly cloudy cells seen 0.5 cloudy at first, then went clear no cells seen 0.3 clear no cells seen Turn over 21 (a) Analyse the data to comment on the effect of the concentration of sodium chloride solution on blood. 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The appearance of the solutions was recorded and samples were observed using a light microscope. When the concentration of glucose solution was below 3%, the solution was clear and no blood cells could be seen. When the concentration of glucose solution was above 3%, the solution was cloudy and blood cells could be seen. When the concentration of sucrose solution was below 6%, the solution was also clear and no blood cells could be seen. When the concentration of sucrose solution was above 6%, the solution was cloudy and blood cells could be seen. Explain the differences in the effects of the solutions of glucose and sucrose. 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Turn over 23 (c) (i) State the part of the brain responsible for osmoregulation. (1) .................................................................................................................................................................................................................................................................................... (ii) Explain how, on a very hot day, the brain ensures that the water potential of the blood remains constant. 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(Total for Question 7 = 12 marks)