6 3 Milk from cows contains a number of different types of lipid. Lipids are made of glycerol and fatty acids. (a) A triglyceride is one type of lipid. Which row of the table describes a triglyceride? (1) Number of molecules Name of bond joining molecules Glycerol Fatty acid A 1 3 glycosidic B 1 3 ester C 3 1 glycosidic D 3 1 ester (b) Fatty acids are either saturated or unsaturated. The diagram shows the structure of an unsaturated fatty acid. HO O C C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H Which row of the table shows the differences between this fatty acid and a saturated fatty acid with the same number of carbons? (1) Number of double bonds in the saturated fatty acid Number of hydrogen atoms in the saturated fatty acid A 0 35 B 0 36 C 1 35 D 1 36 Turn over 7 (c) The table shows the composition of some of the different types of lipid in milk from cows. Type of lipid Composition of lipids in milk from cows (%) monoacylglycerols 0.027 diacylglycerols 0.360 triacyglycerols 97.500 free fatty acids 0.027 phospholipids 0.600 Which row of the table shows the types of lipids that are the median and mode for this set of data? (1) Median Mode A diacylglycerols monoacylglycerols B diacylglycerols triacylglycerols C monoacylglycerols diacylglycerols D monoacylglycerols triacylglycerols (d) Phospholipids have a different structure from other lipids, such as triglycerides. Give one difference in the properties of phospholipids and triglycerides. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 8 (e) Milk from cows also contains a solution of proteins, lactose and mineral ions. The lipids in milk are carried inside milk fat globules (MFG). The diagram shows an MFG. lipids carried inside the MFG outer part of MFG consisting of three layers of phospholipid (i) Complete the diagram to show how nine phospholipid molecules would be arranged in the outer part of an MFG. Use this shape to draw each phospholipid: (2) inside the MFG outside the MFG outer part of MFG consisting of three layers of phospholipids Turn over 9 (ii) Explain the structure of an MFG. 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(Total for Question 3 = 9 marks) 10 BLANK PAGE