Milk is sometimes contaminated with substances such as starch. You will determine the concentration of starch in a sample of contaminated milk, using a range of starch standards. You are provided with the materials shown in Table 1.1. Table 1.1 If any solution comes into contact with your skin, wash off immediately with cold water. It is recommended that you wear suitable eye protection. You will need to carry out a serial dilution of the $$\(1.0 \%\)$$ starch-milk solution, SM, to reduce the concentration by one fifth between each successive dilution. You will need to prepare four concentrations of starch-milk solution in addition to the $$\(1.0 \%\)$$ starch-milk solution, SM. You must use the milk, $$\(\mathbf{M}\)$$, to dilute the starch-milk solution. Do not use water for the dilution. After the serial dilution is completed, you will need to have $$\(8 \mathrm{~cm}^{3}\)$$ of each concentration available to use. Some people are intolerant to lactose in milk. The enzyme $$\(\beta\)$$-galactosidase is used to break down the lactose in milk. In an investigation, equal quantities of $$\(\beta\)$$-galactosidase were added to different concentrations of lactose in milk. The rate of lactose breakdown was measured and recorded. The results are shown in Table 1.2. Table 1.2 (i) Plot a graph of the data in Table 1.2 on the grid in Fig. 1.3. Use a sharp pencil. Fig. 1.3 (ii) Describe and explain the shape of the graph in Fig. 1.3. description ..................................................................................................................... ....................................................................................................................................... . ....................................................................................................................................... . explanation .................................................................................................................... ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... .

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