22   7 One component of the cell surface membrane is the phospholipid bilayer. The diagram shows a phospholipid bilayer. Phospholipid A Phospholipid B (i) A cell surface membrane also contains cholesterol molecules. Name two other types of organic molecule that would be found in a cell surface membrane. (2) 1 ................................................................................................................................................................................................................................................................................. 2 ................................................................................................................................................................................................................................................................................. (ii) The diagram shows two types of phospholipid, A and B. It is possible for phospholipid molecules to have different shapes. Explain what causes these two phospholipids to have different shapes. 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Turn over 23   (b) A phospholipid is a modified triglyceride. Compare and contrast the structures of a phospholipid and a triglyceride. 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(c) The diagram shows a simplified low‑density lipoprotein (LDL). triglyceride cholesterol phospholipid This spherical lipoprotein has a diameter of 27.50 nm. Which of the following shows the circumference (C) of this lipoprotein? Use the formula C = 2πr (1) A 86.39 nm B 172.79 nm C 593.96 nm D 2375.83 nm 24   (d) The concentration of LDL in the blood is a risk factor for cardiovascular disease (CVD). The effect of LDL concentration in the blood on the number of deaths from CVD, in males aged from 25 to 40, was investigated. The graph shows the results of this investigation. 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Number of deaths per 1000 males per year < 100 100–129 130–159 160–189  190 Concentration of LDL in the blood / mg 100 cm–3 (i) Describe the relationship shown in the graph. 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Turn over 25   (ii) The UK population in 2021 was 68 269 157. A student concluded that 81 923 people with an LDL concentration in the blood of 130–159 mg per 100 cm3 died from CVD in 2021. Comment on the validity of this conclusion. Use the information in the graph to support your answer. 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(Total for Question 7 = 14 marks)