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1. Marine mammals have a series of physiological responses to diving. This enables them to stay submerged for long periods in water colder than their body temperature. Collectively these responses are termed the diving reflex. To investigate the diving reflex in humans, heart rate changes in ten healthy subjects were monitored during facial immersions in water ranging from 3°C to 37°C. The data for this experiment is shown below. –5 –10 –15 Percentage change in heart rate –20 –25 –30 –35 0 5 10 15 20 25 30 Water temperature / ºC 35 40 [Source: N R York, Effect of Water Temperature on Diving Reflex Induced Bradycardia in Humans, http://kesler.biology.rhodes.edu/sciJ/York.html] (a) (i) State the effect of facial immersion on heart rate over the range of temperatures shown on the graph. ........................................................................................................................... ........................................................................................................................... (1) (ii) Suggest one reason for the relationship between facial immersion and heart rate. ........................................................................................................................... ........................................................................................................................... (1) (b) Outline the effect of the water temperature on heart rate. ..................................................................................................................................... ..................................................................................................................................... (1) 1 (c) Calculate the heart rate of a person immersed in water at a temperature of 15°C, if their heart rate before immersion was 70 beats per minute. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 5 marks) 2. Cancer of the colon is the fourth most common cancer throughout the world. A number of epidemiological studies have shown that dietary starch and fibre can influence the incidence of colon cancer. The results of two of these studies are shown below. Each point on the graphs represents the human population of one region. 400 300 Starch intake / g day –1 200 13.5 fibre intake / 13.0 g day –1 12.5 12.0 100 11.5 0 11.0 0 10 20 30 Incidence of colon cancer / % 16 17 18 19 20 Colon cancer mortality / deaths per 1000 000 population [Source: adapted from Food, Nutrition and the Prevention of Cancer: a Global Perspective, World Cancer Research Fund, American Institute for Cancer Research, (1997), page 380] (a) Outline the relationship between fibre intake and colon cancer mortality. ..................................................................................................................................... ..................................................................................................................................... (1) 2 (b) (i) Determine the predicted mortality due to colon cancer at a daily fibre intake of 12.5 g day–1 ........................................................................................................................... ........................................................................................................................... (1) (ii) Calculate how much more starch a person would have to consume per day to reduce the cancer risk by 10%. ........................................................................................................................... ........................................................................................................................... (1) (c) Compare the effect of fibre and starch on cancer of the colon. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (d) Discuss the effect of daily fibre intake on lowering the mortality rates of cancer of the colon. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 7 marks) 3 Carotenoids are plant pigments which occur in different forms, such as lutein (from spinach), -carotene (from carrots), and lycopene (from tomatoes). Researchers investigated the processing of carotenoids from vegetables in the stomach and small intestine. Healthy men were fed three test meals differing only in the vegetable added. The carotenoid content of each test meal was the same. Although the meals were basically liquid, the spinach meal had been made from chopped spinach leaves. The meals were ingested in random order with three-week intervals between them. Prior to the first meal, tubes leading directly into the stomach and small intestine were fitted to each man. Samples of stomach and small intestine contents were collected from these tubes at regular intervals after each meal. Data from this study is shown below. Key: 60 Concentration of carotenoids in the stomach / mol dm–3 Concentration of carotenoids in the stomach / mol dm–3 3. 50 40 30 20 10 0 0 60 120 Time / mins = lutein (spinach meal) 180 30 25 20 15 10 5 0 0 = -carotene (carrot meal) 60 120 Time / mins 180 = lycopene (tomato meal) [Source: Tyssandier et al, American Journal of Physiology, 284, (2003), pages 913–922. Copyright 2003 by Am Physiological Society. Reproduced with permission of Am Physiological Soc via Copyright Clearance Center] (a) (i) Calculate the rate of decrease of lycopene concentration in the period 60 minutes to 120 minutes after ingestion in the stomach. ........................................................................................................................... ........................................................................................................................... (1) (ii) Predict how many minutes from ingestion it will take lycopene to completely leave the stomach. ........................................................................................................................... (1) 4 (b) Describe the changes in stomach content of lutein, -carotene and lycopene during the 180 minutes following ingestion. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (c) Suggest a reason why the concentration of lycopene stays relatively constant in the small intestine. ..................................................................................................................................... ..................................................................................................................................... (1) (Total 5 marks) 4. Atherosclerosis is a chronic disease caused by elevated serum cholesterol levels resulting in deposition of lipids in arteries. Diet modification, weight reduction and exercise are initially prescribed to alleviate high cholesterol levels. Due to health and possibly genetic reasons, these attempts may be unsuccessful. Drugs may then be prescribed to lower cholesterol production. One of the enzymes that can be competitively inhibited by these drugs is involved in the pathway for the synthesis of bile and steroid hormones. The safety and effectiveness of a new member of a family of drugs called statins was investigated. The effect of the drug on the blood serum levels of cholesterol, low density lipoproteins (high levels are unhealthy), high density lipoproteins (high levels are healthy) and triglycerides (high levels are unhealthy) are shown below. Serum blood level / % change from baseline Dose of drug / mg Cholesterol Low density lipoproteins High density lipoproteins Triglycerides 0 (placebo) 4 4 –3 10 10 –29 –39 6 –19 20 –33 – 43 9 –26 40 –37 –50 6 –29 [Source: adapted from Parke-Davis, (2000), Lipitor (Atorvastatin Calcium) tablets, Spec #0155G247, page 4, Parke-Davis, New York, www.216.86.213.73/2pdfs/0494lipitor.pdf] 5 (a) State the dose that was most effective in raising the level of high density lipoproteins in the treated groups. .................................................................................................................................... .................................................................................................................................... (1) (b) State the relationship between dose and cholesterol levels. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (2) (c) Distinguish the effect of dose size on low density lipoproteins and high density lipoproteins. .................................................................................................................................... .................................................................................................................................... (1) (d) Explain the use of a placebo in these investigations. .................................................................................................................................... .................................................................................................................................... (1) (e) Suggest one possible physiological side effect when taking statins for atherosclerosis. .................................................................................................................................... .................................................................................................................................... (1) (Total 6 marks) 6