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A2 Biology - Module 6: Digestion Questions 1. Different concentrations of maltose were placed in the small intestine of a mammal. The amount of glucose appearing in the blood and in the small intestine were measured. The results are shown in the graph. Glucose in blood 60 40 Amount of glucose after 15 minutes/ mol dm–1 20 Glucose in lumen of small intestine 0 0 0.2 0.4 0.6 0.8 1.0 Maltose concentration/mmol dm–3 (a) (i) Give the name of the blood vessel most likely to have been sampled for glucose. ........................................................................................................................... (1) (ii) By what chemical process is a molecule of maltose converted into two molecules of glucose? ........................................................................................................................... (1) (b) The enzyme maltase converts maltose into glucose. This enzyme is found in the cell surface membrane of the epithelial cells of the small intestine. (i) Explain the evidence from the graph which supports the view that the breakdown of maltose does not occur in the lumen of the small intestine. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (ii) Suggest an explanation for the shape of the curve showing the change in the amount of glucose in the blood. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3) A2 Biology - Module 6: Digestion Questions A cow obtains most of its nutritional requirements from mutualistic microorganisms in its rumen. The diagram summarises the biochemical processes carried out by these microorganisms. Cellulose Protein Non-protein nitrogen Cellulose Protein Non-protein nitrogen Urea Salivary glands Oesophagus Rumen Methane Fatty acids Amino acids Ammonia Urea Ammonia Microbial protein True stomach and intestine (c) Liver Urea Kidney Use the information in the diagram to help explain why: (i) the relation between the cow and the microorganisms which live in its rumen may be described as mutualistic; ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (ii) (2) it is possible for a cow to survive on a diet which is poor in protein; ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (iii) (2) ruminant animals such as cows are less efficient than non-ruminant animals in converting energy in food into energy in their tissues. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (Total 13 marks) A2 Biology - Module 6: Digestion Questions 2. Answer should be written in continuous prose. Credit will be given for biological accuracy, the organisation and presentation of the information and the way in which the answer is expressed. The diagram shows the nitrogen cycle. Nitrogen-containing substances in producers Digestion Nitrogen-containing substances in primary consumers Digestion Nitrogen-containing substances in secondary consumers Nitrates Nitrates Ammonium compounds Saprobiotic microorganisms Describe how nitrogen-containing compounds in producers are digested in the gut of a mammal. ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... (Total 7 marks) A2 Biology - Module 6: Digestion Questions 3. The flow chart represents the breakdown of starch in the human gut. amylase starch (a) maltase maltose glucose Name two organs which produce amylase in humans. Organ 1 ....................................................................................................................... Organ 2 ....................................................................................................................... (1) (b) Describe how the release of amylase from each of these organs is controlled. Organ 1...................................................................................................................... ................................................................................................................................... ................................................................................................................................... Organ 2...................................................................................................................... ................................................................................................................................... ................................................................................................................................... (3) (c) Describe the precise location of maltase in the human gut. ................................................................................................................................... ................................................................................................................................... (2) (Total 6 marks) A2 Biology - Module 6: Digestion Questions 4. (a) The diagrams show fatty acid molecules in saturated and unsaturated triglycerides. Saturated O H C C C HO Unsaturated C C C O H H H C C C C C C HO H H Complete the diagrams to show the difference between a saturated fatty acid and an unsaturated fatty acid. (2) (b) In the human gut, a triglyceride may be converted to glycerol and fatty acids by hydrolysis. (i) Explain what is meant by hydrolysis. ........................................................................................................................... ........................................................................................................................... (1) (ii) Describe the part played by bile in the hydrolysis of triglycerides. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (Total 5 marks) A2 Biology - Module 6: Digestion Questions 5. Inorganic ions form a minor but essential part of the human diet. (a) Give two functions of each of the following ions in the human body. (i) Calcium 1......................................................................................................................... ........................................................................................................................... 2......................................................................................................................... ........................................................................................................................... (2) (ii) Iron 1......................................................................................................................... ........................................................................................................................... 2......................................................................................................................... ........................................................................................................................... (2) The table shows how the estimated average daily requirements for calcium and iron in the diet vary with age and sex. Age/years (b) Estimated average requirement/mg day–1 calcium iron Both sexes 1 - 3 4-6 7 - 10 275 350 425 5.3 4.7 6.7 Males 11 - 14 15 - 18 19 - 50 50+ 750 750 525 525 8.7 8.7 6.7 6.7 Females 11 - 14 15 - 18 19 - 50 50+ 625 625 525 525 11.4 11.4 11.4 6.7 Explain the change in the estimated average daily requirements for calcium and for iron between the ages of 4 and 10. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) A2 Biology - Module 6: Digestion Questions (c) Explain the differences between the average daily requirements for males and females from the age of 11 for: (i) calcium; ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (ii) iron. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3) The graph shows the results of an investigation of the effect of calcium ion concentration on their rate of uptake by epithelial cells from the small intestine. Curve X Control Cells not treated with respiratory poison Rate of uptake of calcium ions Curve Y Cells treated with respiratory poison A (d) B Concentration of calcium ions in surrounding solution C Explain the evidence from the graph that active transport is involved in the absorption of calcium ions from the lumen of the intestine. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) A2 Biology - Module 6: Digestion Questions (e) For Curve Y, obtained when a respiratory poison was added: (i) explain the shape of the curve between concentrations B and C; ........................................................................................................................... ........................................................................................................................... (ii) suggest why no calcium ions were taken up between concentrations A and B. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3) The diagram shows some of the ways in which other substances are absorbed in the small intestine. Sodium Sodium and glucose Lumen of intestine Water Epithelial cell Research has shown that microorganisms may cause diarrhoea by shutting down the pathway that transports sodium ions into the epithelial cells. These microorganisms do not, however, have any effect on the mechanism responsible for the “co-transport” of glucose and sodium ions into the cells. (f) (i) Explain, in terms of water potential, why a failure to remove sodium ions from the lumen of the intestine causes diarrhoea. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) A2 Biology - Module 6: Digestion Questions (ii) Oral rehydration therapy (ORT) is used to treat diarrhoea. It involves giving the patient a solution of sodium salts and glucose. Using the information in the diagram, explain how this is effective in treating diarrhoea. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (g) (2) Attempts have been made to produce more effective oral rehydration therapy. Suggest why using starch instead of glucose reduces the faecal output for a much longer period. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... 6. (a) (2) (Total 20 marks) Trypsin is a protein-digesting enzyme. It is produced as inactive trypsinogen in the pancreas. Trypsinogen is secreted when food enters the duodenum. (i) Describe the way in which the secretion of trypsinogen is stimulated by food entering the duodenum. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (ii) (2) Describe how trypsinogen is converted to trypsin in the small intestine. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (b) (2) Trypsin is used in the tanning industry for the production of leather. It was first obtained by extracting it from the faeces of domestic animals. Explain why faeces contain digestive enzymes such as trypsin. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 6 marks)