Q1. (a) Name the monosaccharides of which the
Q1. (a) (i) Name the monosaccharides of which the following disaccharides are composed. Sucrose monosaccharides.....................................and....................................... (1) (ii) Lactose monosaccharides.....................................and....................................... (1) (b) Amylase and maltase are involved in the digestion of starch in the small intestine. Complete the table by identifying where these enzymes are produced and the product of the reaction they catalyse. Name of enzyme Where the enzyme is produced Product of the reaction catalysed by the enzyme Amylase Maltase (2) (Total 4 marks) Q2. (a) Some seeds contain lipids. Describe how you could use the emulsion test to show that a seed contains lipids. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (Extra space) ................................................................................................. ........................................................................................................................ ........................................................................................................................ (3) Page 1 of 19 (b) A triglyceride is one type of lipid. The diagram shows the structure of a triglyceride molecule. (i) A triglyceride molecule is formed by condensation. From how many molecules is this triglyceride formed? (1) (ii) The structure of a phospholipid molecule is different from that of a triglyceride. Describe how a phospholipid is different. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... (2) (iii) Use the diagram to explain what is meant by an unsaturated fatty acid. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... (2) (Total 8 marks) Page 2 of 19 Q3. Uric acid is produced in the body. One of the reactions involved in the production of uric acid is catalysed by xanthine oxidase. xanthine oxidase xanthine (a) uric acid A sample of xanthine oxidase was tested by mixing with biuret reagent. Describe and explain the result of this test. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2) (b) Explain why xanthine oxidase is able to catalyse this reaction but it is not able to catalyse other reactions. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2) Page 3 of 19 (c) Gout is a painful condition caused by uric acid crystals in the joints. It is often treated with a drug that inhibits xanthine oxidase. The diagram shows a molecule of xanthine and a molecule of this drug. Xanthine Drug used to treat gout Use the diagram to explain why this drug is effective in the treatment of gout. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (3) (Total 7 marks) Q4. Lactose is present in milk. It is broken down by lactase into glucose and galactose. This is shown in the equation. (a) Name the type of reaction shown in the equation. ...................................................................................................................... (1) (b) The molecular formula of galactose is C6H12O6. What is the molecular formula of lactose? ...................................................................................................................... (2) Page 4 of 19 (c) Doctors use a lactose tolerance test to find out if a person is lactose intolerant. In this test, the person is given a solution of lactose to drink. Blood glucose concentration is then measured over the next two hours. A lactose tolerance test was carried out on a healthy man who was lactose tolerant, and on a man who was lactose intolerant. The results for the first hour are shown in the table. Blood glucose concentration/mmol dm–3 Time/minutes (i) Healthy, lactose tolerant man Lactose intolerant man 0 3.8 3.8 15 4.7 3.9 30 6.1 3.8 45 6.6 3.9 60 6.2 3.9 The blood glucose concentration changed in the healthy man after he had taken the test. Describe how. ............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. (2) (ii) Explain the results for the lactose intolerant man. ............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. (3) (Total 8 marks) Page 5 of 19 Q5. (a) Cholera bacteria produce toxins which increase secretion of chloride ions into the lumen of the intestine Explain why this results in severe diarrhoea (watery faeces) ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (Extra space)................................................................................................. ........................................................................................................................ ........................................................................................................................ (3) Page 6 of 19 (b) Scientists investigated how effective two oral rehydration solutions, A and B, were in treating patients with diarrhoea caused by cholera. • Solution A contained glucose. • Solution B was identical to A, except that glucose was replaced by starch. The graph shows their results. (i) The water potential of solution B was higher (less negative) than the water potential of solution A Explain why. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... (1) Page 7 of 19 (ii) 100 patients were treated with solution A and 100 patients were treated with solution B. Calculate the difference in the number of patients without diarrhoea after 1 day’s treatment with solution A and those without diarrhoea after 1 day’s treatment with solution B. Show your working. Difference in number of patients ..................................... (2) (Total 6 marks) Q6. The diagram shows part of the gut wall of an animal. (a) (i) Name the structure labelled X. ............................................................................................................. (1) Page 8 of 19 (ii) Describe the function of the layer labelled Y. ............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. (2) (b) Describe and explain how two features shown in the diagram increase the rate of absorption of digested food. Feature 1 Description ...................................................................................................................... ...................................................................................................................... Explanation ...................................................................................................................... ...................................................................................................................... Feature 2 Description ...................................................................................................................... ...................................................................................................................... Explanation ...................................................................................................................... ...................................................................................................................... (4) (Total 7 marks) Page 9 of 19 Q7. The diagram shows a cell from a potato. (a) Give two features which may be found in a prokaryotic cell which would not be found in this cell. 1 ................................................................................................................... 2 ................................................................................................................... (2) (b) (i) Describe how you could confirm that the granules contained starch. ............................................................................................................. ............................................................................................................. (1) ............................................................................................................. (ii) Name one polysaccharide other than starch that would be found in this cell. ............................................................................................................. (1) (c) Explain one advantage of storing starch rather than glucose in potato cells. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2) (Total 6 marks) Page 10 of 19 Q8. The diagram shows one method by which amino acids are absorbed from the small intestine into the blood. They are co-transported into the epithelial cell with sodium ions (Na+) at point X on the diagram. Normally, the concentration of sodium ions inside the epithelial cell is low. Source: adapted from M. ROWLAND, Biology (University of Bath Science 16-19) (Nelson Thornes) 1992. Dinitrophenol (DNP) prevents oxidative phosphorylation. When treated with DNP, the sodiumpotassium pump at Y no longer works. As a result, the concentration of sodium ions in the cell rises and amino acid absorption stops. (i) Explain why pump Y will not work in the presence of DNP. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2) Page 11 of 19 (ii) Explain why sodium ions and amino acids are not absorbed from the lumen of the small intestine in the presence of DNP. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2) (iii) By what mechanism would amino acids leave the epithelial cell at point Z? ...................................................................................................................... (1) (Total 5 marks) Q9. (a) Describe how you would use a biochemical test to show that a solution contained protein. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2) The diagram shows the structure of two amino acid molecules, tyrosine and phenylalanine. (b) Copy from the diagram the R group in the phenylalanine molecule. (1) Page 12 of 19 (c) (i) In the space below, draw the chemical bond formed when these two amino acids are joined by condensation. You need only draw the parts of the molecules shown in the box. (2) (ii) Name this bond. ............................................................................................................. (1) (d) Tyrosine can be made in the body by hydroxylating phenylalanine. Use the diagram to explain the meaning of hydroxylating. ...................................................................................................................... ...................................................................................................................... (1) (Total 7 marks) Page 13 of 19 M1. (a) (i) Glucose and fructose; Ignore reference to alpha and beta Either way around 1 (ii) Glucose and galactose; Ignore reference to alpha and beta Either way around 1 (b) 1. (Amylase) pancreas, produces maltose; Place and product = 1 mark (mark horizontally) 2. (Maltase) in / on epithelium (of small intestine), produces glucose; Ignore references to salivary glands or saliva Accept wall / lining of small intestine Ignore reference to cells alone Ignore reference to ribosomes / rER 2 [4] M2. (a) 1. Crush / grind; 2. With ethanol / alcohol; 3. Then add water/then add to water; 2 Water must be added after ethanol for third mark. 4. Forms emulsion / goes white / cloudy; 4 Do not accept carry out emulsion test. 3 (b) (i) 4 / four; 1 (ii) 1. Phosphate / PO4; “It” refers to phospholipid. 2. Instead of one of the fatty acids / and two fatty acids; 1 Accept minor errors in formula. Do not accept phosphorus / phosphorus group. 2 Page 14 of 19 (iii) 1. Double bonds (present); Answer refers to unsaturated unless otherwise clearly indicated. 2. Some / two carbons with only one hydrogen / (double bonds) between carbon atoms / not saturated with hydrogen; 1 and 2. May be shown in appropriate diagram. 3. In (fatty acid) C / 3; 2 max [8] M3. (a) Lilac/purple/mauve/violet; Xanthine oxidase is a protein; Reject pink or blue as the resulting colour with biuret. 2 (b) Substrate has specific shape; Allows binding/fitting/forms ES complex with active site; Or Active site has specific shape; Allows binding/fitting/forms ES complex with substrate; Accept structure ≡ shape 2 (c) Xanthine similar shape to drug; Drug fits active site/competes for active site/is a competitive inhibitor; Less/no uric acid formed; 3 [7] M4. (a) Hydrolysis; 1 (b) C12; H22O11; 2 (c) (i) One mark for answer that simply refers to increase and subsequent decrease Two marks for answer that refers to reaching a peak at approximately 6.6 mol dm–3/45 minutes. Q Descriptions must refer to concentration of glucose and time to gain credit. Do not accept vague references to “It . . .” 2 Page 15 of 19 (ii) No lactase; Therefore lactose not digested/glucose not produced; No glucose absorbed therefore concentration in blood stays the same/does not rise; 3 [8] M5. (a) 1. Water lost into gut / water moves into gut / water leaves cells; QWC ignore large / small WP QWC ignore reference to high / low concentrations of water or high / low concentrations of solution 2. Low(er) water potential of intestine / gut (lumen); 3. Osmosis / movement down a WP gradient; Ignore reference to stomach 4. Less / not enough water (re)absorbed; QWC ignore ‘along’ concentration gradients 3 max (b) (i) Starch is not (very) soluble / does not dissolve well; Accept converse for glucose in A Ignore ‘starch is osmotically inactive’ Ignore reference to solute potentials 1 (ii) 55;; 2 marks for correct answer Working: 5% for A and 60% for B; Max 1 if answer as a % 2 [6] M6. (a) (i) villus; (reject microvilli) 1 (ii) contracts / peristalsis; moves/pushes/forces food through gut; 2 Page 16 of 19 (b) many / projecting villi (X) (no double penalty for microvilli); large surface area (for absorption); large/good blood supply / many capillaries/blood vessels; maintains concentration gradients / efficient removal of digested products; thin outer layer / blood vessels near to surface; short diffusion pathway; 4 max [7] M7. (a) Any two from: Loop of DNA; Non-cellulose cell wall; Plasmid; Capsule; Flagellum; Mesosome; Accept small ribosomes 2 (b) (i) (Granules) turn blue-black/dark blue/black/purple with iodine; 1 (ii) Cellulose / pectin; 1 (c) Use principle: Feature of starch; Consequence in terms of storage; e.g. Insoluble; Therefore will not “wash” out of cell / affect water potential / affect osmosis; OR Molecule coiled/branched; Therefore large amount stored in small space / compact OR Does not affect water potential; So no effect on entry of water (into cell); 2 [6] M8. (i) Lack of ATP; Pump = active transport / requires energy / ATP provides energy / transport is up concentration gradient; 2 Page 17 of 19 (ii) Concentration of Na+ inside cell no longer less than concentration in gut lumen /no longer a concentration gradient; No (facilitated) diffusion of NA+ ions possible / amino acid absorption requires diffusion of Na+ ions into cell; 2 (iii) Diffusion / facilitated diffusion; 1 [5] M9. (a) (i) Biuret / alkali + copper sulphate; Lilac/purple/mauve/violet; Do not give credit for blue or pink. Ignore references to heating. 2 (b) R group of phenylalanine copied accurately; 1 (c) (i) Bond shown linking carbon and nitrogen; OH and H removed, =O and –H remaining; 2 (ii) Peptide bond; 1 (d) Addition of hydroxyl/OH group; Candidate must distinguish clearly between hydroxylation and hydrolysis 1 [7] Page 18 of 19 Page 19 of 19
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