RI N21 H2 P3 answers

Section A 1 (a) Suggest and explain three different hypotheses, other than those related to diet, that could account for any of the trends shown in Table 1.1. At least one of the hypotheses must refer to TB and at least one must refer to CVD. [6] Hypotheses about [quote data] tuberculosis death rate decreasing gradually over the years from 1900 to 2015, from 195 to 1 per 100 people per year respectively: 1. Development of antibiotics to treat infected TB patients since TB is caused by Mycobacterium tuberculosis bacterial infections which can be treated with bacteriocidal and/or bacteriostatic antibiotics; 2. Vaccination programme so that US citizens have herd immunity to prevent the spread of TB, reducing the number of deaths; 3. Vaccination programme to produce memory B cells in individuals so that there is a faster, larger secondary immune response which reduce the death rate; 4. Increased awareness about the need to isolate infected patients as preventative measures so that the Mycobacterium tuberculosis bacterial infections which are transmitted by airborne means are limited in spread; Hypotheses about [quote data] CVD death rate first increasing from 1900 to 1950, from 250 to 450 per 100 people per year respectively, and then decreasing from 1950 to 2015, from 450 to 220 per 100 people per year respectively: 5. Increase in stress due to work as US economy became more industrialised from 1990 to 1950, and an improvement in emergency healthcare or drugs from 1950 to 2015; 6. Lack of awareness about CVD being caused by a sedentary lifestyle from 1990 to 1950, and a greater awareness of active lifestyle from 1950 to 2015; At least 1 from points 1-3 and 1 from points 5-6. (b) (i) Draw a line of best fit on Fig. 1.1. [1]

(ii) Explain what is shown by the slope of the line of best fit you have drawn on Fig. 1.1. [1] 1. An increase in percentage of energy intake in the diet that comes from saturated fatty acids is correlated to (Reject: cause) a proportional increase in concentration of cholesterol in the blood; 2. [Quote Data] E.g. An increase from 6.6% to 20.2% of energy intake in diet that comes from saturated fatty acids is seen to correspond to an increase in 1.8 mg cm- 3 to 2.6 mg cm-3 of cholesterol in blood; (iii) Distinguish between a triglyceride and a fatty acid. [2] 1. A triglyceride is hydrophobic due to the absence of carboxylic acid groups, while a fatty acid is hydrophilic due to the presence of carboxylic acid groups; 2. A triglyceride has a glycerol joined to three fatty acids by three ester linkages, while a fatty acid does not have any ester linkage and no glycerol; (iv) State two roles of cholesterol in cells. [2] 1. Cholesterol provides mechanical stability as it forms weak hydrophobic interactions with neighbouring hydrocarbon chains of phospholipids; 2. Cholesterol regulates membrane