Daniela DuránDiploma Biology 2013/2014/2015 1 IB DIPLOMA BIOLOGY PAST PAPER QUESTIONS ON DIGESTION A Test •Answer Q’s 1 to 4 by drawing a circle around the best answer. •Answer the remaining questions in the spaces provided. •Question 10 is for HL only. •Total marks: HL 46 SL 36 John Osborne October 2014 Daniela Durán Diploma Biology 2013/2014/2015 2 1. Which of the following is correct regarding the enzymes listed in the table? Enzyme Amylase Lipase Protease A. Substrate Polysaccharide emulsified fat dipeptide or polypeptide B. Substrate emulsified fat dipeptide or polypeptide polysaccharide C. Product amino acids small polysaccharides or monosaccharides fatty acids and glycerol D. Product small polysaccharides or monosaccharides amino acids fatty acids and glycerol (Total 1 mark) 2. What does the digestion of starch by amylase produce? A. Lactose B. Sucrose C. Galactose D. Maltose (Total 1 mark) 3. In the digestive system, enzyme A has an optimum pH of 1.5 and enzyme B an optimum pH of 7. What are the possible substrates of these enzymes? Enzyme A Enzyme B A. proteins amino acids B. lipids proteins C. carbohydrates lipids D. proteins lipids (Total 1 mark) 4. Two cellular activities that support human life are absorption and assimilation. What is needed for assimilation but not for absorption? A. Enzymes to synthesize new molecules B. Blood capillaries C. Dissolved nutrients D. Microvilli (Total 1 mark) Daniela Durán Diploma Biology 2013/2014/2015 3 5. The diagram below shows a transverse section of the ileum. [Source: P H Raven and G B Johnson, Biology, (2002), 6th edition, McGraw-Hill, page 1024] (a) (i) State the name and function of the structures labelled 1 and 2. 1: Villus, increase intestinal absorptive surface area 2: Lacteal, collect absorbed triglycerides and cholesterol (2) (ii) Distinguish between the muscles labelled 3 and 4. Muscle 4 is a circular muscle while Muscle 3 is a longitudinal muscle. (1) (Total 3 marks) Daniela Durán Diploma Biology 2013/2014/2015 4 6. Draw a labelled diagram of the digestive system. (Total 5 marks) Daniela Durán Diploma Biology 2013/2014/2015 5 7. Carbohydrates are one of the constituents of a balanced diet in humans, (a) Carbohydrates can be used as a substrate in cell respiration. (i) State one other constituent of human diets that can be used as a respiratory substrate. Water (1) (ii) Outline two uses of carbohydrates in the human body, other than as a respiratory substrate. 1. Carbohydrates can be broken down into smaller saccharides and used in the production of new proteins 2. Carbohydrates can be found in the cytoplasm of cells (2) (b) Monosaccharides are useful if energy is needed rapidly, but polysaccharides are a better form of carbohydrate if energy is needed over a longer period. (i) State two foods that are a good source of monosaccharides. 1. Honey 2. Milk (1) (ii) State two foods that are a good source of polysaccharides. 1. Bread 2. Pasta (1) (Total 5 marks) 8. (a) Describe how the ileum uses active transport in the absorption of food. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (b) List two substances resulting from the breakdown of haemoglobin in the liver. ..................................................................................................................................... (1) (Total 4 marks) 9. Researchers extracted an enzyme from the human digestive system and tested its activity at different pH values on proteins extracted from the blood of cows. The results are shown in the Daniela Durán Diploma Biology 2013/2014/2015 6 graph below. Enzyme activity 1 2 3 4 pH a) Deduce from where in the human digestive system this enzyme was extracted. [1] Stomach b) Outline the need for enzymes in the digestive system. [2] Enzymes are necessary in digestion because they act as catalysts for the hydrolysis of complex organic molecules into their monomers. They do this by lowering the activation energy required for hydrolysis to start. c) State one function of the large intestine. [1] short-term waste storage d) Explain how the structure of the villus is adapted for absorption. [3] The villus is shaped like many fingers, increasing surface area and therefore maximising absorption. It also has a direct link to the blood supply via capillaries, making absorption and transportation quicker and easier. (4) (Total 7 marks) 10. HL Enzymes are used by living organisms to catalyse reactions. Some of these reactions occur in the cytoplasm of cells. Other reactions take place outside cells, for example the digestion of foods in the human gut. (a) State the name used by biochemists for the chains and cycles of reactions that occur inside cells. Cell metabolism (1) Daniela Durán Diploma Biology 2013/2014/2015 7 (b) Enzymes of digestion in humans are secreted by glands. They have a pH optimum which allows them to work efficiently in the part of the gut into which they are secreted. (i) In the table below, identify the missing enzyme, the two glands, and the pH optimum Name of enzyme Gland secreting the enzyme Substrate Products pH optimum amylase Salivary glands starch maltose 7 Pancreatic lipase Pancreas triglycerides fatty acids and glycerol 7 (4) (ii) Outline the effect of pH values above and below the optimum on enzyme structure. Enzymes become uncoiled, and, as they lost their shape, lose their ability to metabolize their specific substrates. (2) (c) Enzymes that work inside cells are sometimes affected by non-competitive inhibitors. Explain how a non-competitive inhibitor affects the activity of an enzyme. A non-competitive inhibitor may become attached and block an enzyme’s active site. This prevents substrates from attaching to the enzyme to be broken down, stopping enzyme activity. (3) (Total 10 marks) Daniela Durán Diploma Biology 2013/2014/2015 8 11. Osteoporosis is a major health problem for many post-menopausal women. As the ovaries reduce their secretion of estrogen, calcium is gradually lost from bones, weakening them and increasing the chance of fractures. To test whether diet influences the rate of calcium loss, ovaries were removed from groups of female rats and the rats were then either fed a control diet or the same diet with one gram of a supplementary food per day. The rate at which the rats excreted calcium was measured. The ratio of calcium loss between the control rats and the rats that were given a supplementary food was calculated. rats control in loss food ary supplement with loss Ratio . The results are shown in the graph below. Calcium loss ratio 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Supplementary food c a b b a g e e g g g a r l i c p a r s l e y m e a t o n i o n p o t a t o s k i m m e d m i l k s o y - b e a n t o m a t o [Source: Muhlbauer and Li, Nature, 1999, 401, pages 343–344] (a) (i) Identify which supplementary food was most effective in reducing calcium loss. Parsley (1) (ii) Identify which supplementary food was least effective in reducing calcium loss. Egg (1) (b) Among the ten foods shown in the graph, seven are plant products (vegetables) and three are animal products. Discuss whether the plant or the animal products were more effective at reducing calcium loss. Egg and meat, both animal product, showed a higher ratio of calcium loss than most of the plants, such as parsley, garlic and cabbage. Skimmed milk, however, has a lower ratio, lower than soy-bean and potato supplements. On the whole, however, most of the plant products have a ratio lower than that of meat products, at least 0.1 units lower. (3) (c) Suggest a trial, based on the results shown in the graph, that could be done to try to reduce osteoporosis in humans. Run a trial with women in the menopause stage, with a control group and several groups taking different supplements. Examples of supplements could include (3) (Total 8 marks)