Turn over 7 3 The structure of a lipid relates to its role in living organisms. (a) Triglycerides are lipids. (i) The diagram shows part of a glycerol molecule and part of a fatty acid. Complete the diagram to show the ester bond joining the fatty acid to the glycerol molecule. (1) C C O rest of fatty acid molecule rest of glycerol molecule (ii) The table shows the relative atomic mass of some elements. Element Relative atomic mass carbon 12 hydrogen 1 nitrogen 14 oxygen 16 A triglyceride is made from a glycerol molecule and three fatty acids. The molecular mass of the glycerol is 92 and the total molecular mass of the three fatty acids is 362. Which is the molecular mass of this triglyceride? (1) A 400 B 436 C 448 D 454 8 (b) The type of lipid in the diet of a person can affect their risk of developing atherosclerosis. The table shows the percentage content of different lipids in some products used to cook food. Product Source of product Saturated lipids Monounsaturated lipids Polyunsaturated lipids Other lipids Omega-6 Omega-3 Beef fat animal 45 39 3 1 12 Butter animal 52 24 2 1 21 Rapeseed oil plant 7 59 20 9 5 Safflower oil plant 10 15 75 0 0 (i) The pie chart shows the approximate ratio of the lipids in beef fat. monounsaturated saturated polyunsaturated other Complete the pie chart to show the approximate ratio of the lipids in safflower oil. (1) Turn over 9 (ii) Calculate the difference in mass of polyunsaturated lipid in 500 g of safflower oil and 500 g of beef fat. (2) Answer ................................................................ g (iii) Explain why cooking food using plant products rather than animal products could lower the risk of developing atherosclerosis. 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(c) Cell membranes contain lipids that have a phosphate group attached to the glycerol, instead of one of the fatty acids. Explain the importance of the phosphate group in these lipids. 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(Total for Question 3 = 9 marks)