Biology · 2011 · May · Paper 3 · SL · TZ1 · Question paper

Examination code 2 2 1 1 – 6 0 1 2 33 pages M11/4/BIOLO/SP3/ENG/TZ1/XX Thursday 19 May 2011 (morning) Biology STANDARD level PAPeR 3 INSTRUCTIONS TO CANDIDATES • Write your session number in the boxes above. • Do not open this examination paper until instructed to do so. • Answer all of the questions from two of the Options. • Write your answers in the boxes provided. 1 hour [Personal identifier removed] © International Baccalaureate Organization 2011 0136 2211601 2 – 2 – M11/4/BIOLO/SP3/ENG/TZ1/XX Option A — Human nutrition and health 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. 3 6 12 18 –6 0 5 10 15 25 Urinary vitamin C / mg 9 20 Vitamin C loading Time / hours Key: ascorbic acid dehydroascorbic acid Masaru TSUJIMURA, Shizu HIGASA, Kazuhiro NAKAY AMA, Y oshiko Y ANAGISAW A, Sadahiko IW AMOTO and Y asuo KAGAW A. 2008. ‘Vitamin C Activity of Dehydroascorbic Acid in Humans — Association between Changes in the Blood Vitamin C Concentration or Urinary Excretion after Oral Loading’. J. Nutr. Sci. Vitaminol., 54: 315-320, 1 table. ( a) State the urinary vitamin C content for each of the two study groups six hours before vitamin C loading. [1] Ascorbic acid : .................................................... Dehyrdoascorbic acid: .................................................... (This question continues on the following page) 0236