2011年5月IB生物SL真题下载-Paper3
A1. Vitamin C is an important component of a healthy diet. Because it is water-soluble it cannot be effectively stored and excess vitamin C is released in the urine. In order to investigate the ability of the body to retain different chemical forms of vitamin C, 17 healthy, female university students, between the ages of 18 and 22, were placed on a low vitamin C diet (< 5 mg per day) for three days. The test subjects were divided into two groups and were given an oral vitamin C loading of either ascorbic acid (176 mg) or dehydroascorbic acid (174 mg). Levels of vitamin C in the urine were measured six hours before and at regular intervals over a 24 hour period following vitamin C loading. The negative value indicates time before vitamin C loading.
(a) State the urinary vitamin C content for each of the two study groups six hours before
vitamin C loading.
Ascorbic acid:
Dehyrdoascorbic acid:
(b) Calculate the percentage increase in urine levels of vitamin C for the ascorbic acid study group during the first three hours after vitamin C loading.
. . . . . . . . . . . . . . . . . . . . . . . %
(c) Compare the trends in vitamin C release for the two test groups during the first twelve hours after vitamin C loading.
(d) Large individual differences in the urine level of ascorbic acid and dehydroascorbic acid were recorded between test subjects after 24 hours. Suggest one possible reason for these large individual differences.
(e) Scurvy is a disease that is due to vitamin C deficiency. Evaluate the importance of this investigation for finding ways to combat vitamin C deficiency.
A2. (a) Body mass index (BMI) can be calculated from the mass (in kg) and height (in m) of an individual. The status of an individual can then be determined from a scale such as the one shown below.
(i) Calculate the BMI for an individual whose mass is 74.0 kg and who has a height of 1.80 m.
(ii) On the basis of the BMI calculated in (a)(i), identify the status of this individual.
(b) Outline factors that can lead to an individual becoming obese.
A3. (a) State two advantages of breastfeeding over bottle-feeding.
(b) State one symptom of type II diabetes.
(c) Explain the dietary advice that should be given to a patient who has developed type II diabetes.
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