IGCSE Cambridge (CIE) Biology Enzymes PDF Past Paper

IGCSE Cambridge (CIE) Biology 2 hours 15 questions Theory Questions Enzymes Enzymes / Enzyme Investigations / Enzyme Action & Specificity / Enzymes & Temperature / Enzymes & pH Easy (5 questions) /49 Scan here...

IGCSE Cambridge (CIE) Biology 2 hours 15 questions Theory Questions Enzymes Enzymes / Enzyme Investigations / Enzyme Action & Specificity / Enzymes & Temperature / Enzymes & pH Easy (5 questions) /49 Scan here for your answers or visit savemyexams.com Medium (5 questions) /44 Hard (5 questions) /52 Total Marks /145 © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 1 Easy Questions 1 (a) This question is about enzymes. Choose words from the list to complete the sentences. Each word may be used once, more than once, or not at all. amino acid amylase bacteria biological fatty acid glucose humidity lipase living protease salivary temperature All enzymes are proteins. Proteins are made of......................................................... An enzyme acts as a......................................catalyst. In order to work rapidly, enzymes need the correct......................................... and pH. An example of an enzyme that works in the acidic conditions in the stomach is............................................................ Acidic conditions will kill many of the.................................................................... present in food. Salivary............................................................ stops working in acidic conditions. Fats are broken down by........................................................ © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 2  (7 marks) (b) Match up the key terms to their definition. Enzyme Groove in enzyme where the reaction take place Substrate Molecules that bind to an enzyme Catalyst One enzyme for one substrate Specificity Any molecule that speeds up reactions Active site A protein that speeds up reactions (5 marks) (c) Extended Define what is meant by the term enzyme-substrate complex. (1 mark) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 3 2 (a) Fig. 1 shows a model of how an enzyme works. Fig. 1 Label the enzyme molecule on Fig. 1. (1 mark) (b) Enzymes are biological catalysts. (i) Explain what is meant by the term catalyst. (ii) State why enzymes are important in organisms. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 4  (3 marks) (c) Sketch in the appearance of an enzyme-substrate complex on the diagram in Fig. 1. The diagram is provided again here for you. Fig. 1 (1 mark) (d) Extended only Describe the action of enzymes. Use the following words as part of your answer: collide complementary randomly recycled (4 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 5 3 (a) Extended only The digestive systems of young mammals are not fully developed. Enzymes such as amylase, maltase and protease are often added to baby food to aid chemical digestion. (i) Complete Table 1 by stating the substrate and product(s) for each enzyme reaction. Table 1 enzyme substrate product(s) amylase maltase protease (ii) Suggest why the temperature of baby food must be controlled when the enzymes are added. (iii) State one other condition that must also be controlled to optimise enzyme activity. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 6  (6 marks) (b) The optimum temperature for the enzymes in the baby food to work was found to be 37°C. Fig. 1 below shows a graph of the activity of an enzyme as temperature increases. Fig. 1 Label the following key terms on to the graph: © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 7  Optimum temperature Denatured enzyme (2 marks) (c) The label on the jar of baby food states that food must be thrown away if heated above 37°C. Explain the need for this label. (2 marks) (d) Any food must be heated to its correct temperature as specified on cooking instructions. State another reason why it is important to heat food to the correct temperature. (1 mark) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 8 4 (a) A student investigated the effect of pH on the activity amylase on starch solution. The student used iodine solution as an indicator to see when the amylase was active. Their results are shown in the table below. pH of solution time for iodine test to stop turning blue-black / seconds 2 196 4 187 6 42 8 54 (i) Describe why the student used iodine solution. (ii) Calculate the range of results for the time in seconds (4 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 9 (b) (i) State which of the pH values tested is the optimum for amylase. (ii) Explain your answer to part (i) (2 marks) (c) Another student concluded that the optimum pH was not shown in the results in Table 1. Explain why the student concluded this. (3 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 10 5 (a) Fig. 1 represents the reactants and products in a chemical reaction and four different enzymes (A, B, C or D). Fig. 1 State the letter of the enzyme responsible for this reaction. (1 mark) (b) State what happens when a substrate with a shape that is not complementary to the enzyme tries to enter the active site. (2 marks) (c) A student investigated the effect of enzyme concentration on the mass of product formed in one hour. Fig. 2 shows the results of this investigation. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 11 concentration of enzyme / arbitrary units mass of product formed / grams 5 15 10 22 15 25 20 32 25 38 30 40 35 40 40 40 Fig. 2 © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 12  Complete the graph by plotting the points and drawing a line to show the trend in the data. The first three points have been plotted for you. (2 marks) (d) Describe the effect that enzyme concentration has on the mass of product formed. (2 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 13 Medium Questions 1 (a) The effect of temperature on enzyme activity was investigated. The results are shown in Fig. 1. Fig. 1 (i) State the optimum temperature for the enzyme in Fig. 6.1. Give your answer in °C. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 14  (ii) State why there is no enzyme activity at 60 °C. (2 marks) (b) State one factor other than temperature that affects enzyme activity. (1 mark) (c) Table 1 shows some large insoluble molecules, some digestive enzymes and some smaller soluble molecules that are produced during digestion. Table 1 insoluble molecule enzyme soluble molecules starch amylase reducing sugars fat protease Complete Table 1 by writing the names of the missing enzyme and molecules. The first row has been done for you. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 15  (5 marks) (d) List the chemical elements present in fats. (1 mark) (e) State where in the digestive system protease is secreted. (1 mark) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 16 2 (a) Catalase is an enzyme that catalyses the breakdown of hydrogen peroxide into water and oxygen. The effect of temperature on catalase activity was investigated. The results are shown in Fig. 1 Fig. 1 (i) State the temperature at which catalase is most active in Fig. 1. Give your answer in °C. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 17  (ii) Explain why there is no enzyme activity at 60°C. (2 marks) (b) State one factor other than temperature that affects enzyme activity. (1 mark) (c) Digestive enzymes are used in chemical digestion to break down large insoluble molecules to smaller soluble molecules. The boxes show some large insoluble molecules, some digestive enzymes and some smaller soluble molecules that are produced during digestion. Draw one straight line from each enzyme to the insoluble molecule it acts on. Draw another line from each enzyme to the smaller soluble molecule that is produced. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 18  Draw a total of six lines. (5 marks) (d) Digestive enzymes are secreted in different parts of the body. Gastric proteases are found in the stomach. Suggest the optimum pH for gastric protease. (1 mark) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 19 3 (a) Extended only Fig. 1 shows an enzyme in its optimum pH and in a pH that is much lower. Fig. 1 Describe what has happened to the enzyme. (2 marks) (b) Extended only Sketch an appropriate substrate for the enzyme shown in Fig. 1 (1 mark) (c) Extended only A farmer tested a range of pHs on the soil in a section of a field and recorded the percentage of germination of carrot seedlings at each pH. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 20  Fig. 2 shows the results. Fig. 2 Describe and explain which pH is the optimum pH for the carrot seedlings. (2 marks) (d) Extended only Another farmer suggested they plant radish seedlings at the carrot seedling's optimum pH shown in Fig. 2. Explain why this farmer's suggestion may be incorrect. (2 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 21 4 (a) During the fermentation of yeast, enzymes that break down sugar release carbon dioxide gas. The volume of carbon dioxide released can be used to measure how fast these enzymes are working. A student investigates if fermentation works faster at two different temperatures: 25°C or 30°C. They measured the volume of carbon dioxide released in 15 minutes. Fig. 1 shows the apparatus she uses. Fig. 1 The student used a gas syringe, as shown in Fig. 1 to collect and measure the volume of carbon dioxide released. They could have measured the volume of carbon dioxide by collecting the gas over water in a measuring cylinder. Use the information provided in Fig. 1 to suggest why it is better to use a gas syringe. (1 mark) (b) The student’s results are shown in Table 1 © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 22  temperature (°C) volume of carbon dioxide gas released in 15 minutes / cm3 repeat 1 repeat 2 repeat 3 25 25 22 24 30 33 26 35 (i) Calculate the mean rate of gas produced at 25°C in cm3/minute. Give your answer to 1 decimal place. (ii) The rate of gas produced at 30°C is greater than at 25°C. Use your knowledge of enzymes to explain why. (iii) The teacher tells the student to repeat the results for 30°C. Explain why the teacher advised this. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 23  (7 marks) (c) Extended Enzymes can be inhibited by chemicals called phenols during fermentation. Phenols bind to amino acids on enzyme molecules. Suggest how phenols inhibit enzymes. (2 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 24 5 (a) Extended only Salivary amylase is an enzyme that is produced and secreted by salivary gland cells in the mouth. Carbohydrate digestion, by amylase, begins in the mouth. Starch, a polysaccharide, is hydrolysed into the disaccharide maltose by the enzyme salivary amylase. The effect of changing pH and temperature on the digestion of starch was investigated by a group of students. The results are shown in Table 1 and Table 2 below. Table 1 - Effect of pH pH time taken to digest starch / minutes 3.0 38 4.0 26 5.0 17 6.0 13 7.0 7 8.0 8 Table 2 - Effect of temperature © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 25  temperature / C time taken to digest starch / minutes 10 20 20 14 30 11 40 6 50 12 60 23 A student reads the following statement on the Internet: ‘The main site for carbohydrate digestion is the small intestine.’ One of the students states that salivary amylase must be responsible for digesting starch in the small intestine. The student is incorrect. Use the results in Table 1 to explain why. (3 marks) (b) Using the results shown in Table 2, explain how temperature affects digestion. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 26  (3 marks) (c) Extended only A second form of amylase, pancreatic amylase, is responsible for continued carbohydrate digestion in the small intestine. Explain how the digestion of food by enzymes in the intestine is not inhibited by the acid produced in the stomach. (2 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 27 Hard Questions 1 (a) Extended only The pancreas is an organ that produces enzymes used in digestion. Explain the importance of enzyme specificity in the digestion of food. (4 marks) (b) Extended only Pancreatic cancer develops when a malignant tumour grows inside the pancreas. One symptom of pancreatic cancer is weight loss. With reference to enzymes, explain how pancreatic cancer may cause a person to lose weight. (4 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 28 (c) Extended only Certain types of antibodies, called monoclonal antibodies, have been used to treat pancreatic cancer. Compare the activity and nature of antibodies with those of enzymes. (3 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 29 2 (a) Extended only Biological washing powders contain enzymes and have to be used at temperatures below 45 °C. Stains on clothes that are washed at temperatures above 45 °C are not always removed. Explain why. (2 marks) (b) Extended only Thermophilic bacteria are a special type of bacteria that live in hot springs at temperatures of 80 °C. Scientists have extracted enzymes from thermophilic bacteria. The scientists added these enzymes to biological washing powder in the lab and tested them on a range of lab produced stains on cotton cloth. It is expected that by using the washing powder the user can increase the cleaning performance of their laundry cycle. Suggest why. (2 marks) (c) Extended only The scientists compared two different washing powders each containing a different enzyme from thermophilic bacteria. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 30  They washed stained items of clothing for different periods of time and recorded the percentage of stain removal. Their results are shown in Fig.1 below. Fig. 1 Compare the results of the two washing powders. (4 marks) (d) Extended only A scientist released a report with the claim, "A 30 minute wash can rid your clothes of 95% of stains with new thermophilic washing powder". Evaluate this claim. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 31  (3 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 32 3 (a) Enzymes are involved in controlling cell division. Fig. 1 shows how cell division can be accelerated by two enzymes, enzymes X and Y, in cancerous liver cells. Most cancer cells produce both enzymes X and Y. Cancer cells are likely to develop into cancerous tumours inside the liver by uncontrolled cell division. Fig. 1 Some people carry a genetic mutation that inhibits enzyme X. A drug company has produced a medicine that inhibits enzyme Y. This medicine has been trialled in people who have the mutation and liver cancer. The medicine has been found to be successful at treating liver cancer. Explain why. (3 marks) (b) Explain why the medicine could not be used to treat liver cancer in a patient that does not have the genetic mutation. © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 33  (2 marks) (c) Extended only Glutaminase is another enzyme that has shown success in treating cancer. It is within a group of enzymes called amino acid deprivation enzymes which act on and destroy specific amino acids in cancerous cells. Explain the action of the glutaminase on amino acids in cancer cells. (4 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 34 4 (a) Extended only Fig. 1 illustrates the results of two enzyme-controlled reactions involving two different types of enzyme. Fig. 1 From these reactions, determine what conclusion can be drawn about the function of enzymes. (2 marks) (b) Extended Catalase is an enzyme found in many different tissues in plants and animals. It speeds up the rate of the following reaction. Fig. 2 A scientist investigated the effect of pH on the activity of the enzyme catalase in a geranium plant. Table 1 shows the scientist's results. Table 1 © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 35  pH catalase activity / arbitrary units Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Mean 2.0 0 0 0 0 0 0 2.5 2 3 3 2 4 3 3.0 12 12 9 8 10 10 3.5 15 26 16 14 17 4.0 25 23 29 24 22 25 4.5 32 30 35 36 35 34 5.0 46 44 42 45 42 44 5.5 54 52 55 52 51 53 6.0 58 59 58 60 62 60 6.5 42 40 45 43 42 42 Calculate a mean result for pH 3.5 (3 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 36 (c) Extended Use the grid below to draw a graph of the scientist's results. Fig. 3 (4 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 37 (d) Extended Use Table 1 and the graph to answer the following: (i) Describe the results shown in the graph. (ii) Predict the catalase activity at pH 7. (iii) Explain why the catalase activity is zero at pH 2. (5 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 38 5 (a) A group of students carried out the following practical to establish the effect of temperature on protein breakdown: Place a drop of biuret solution into every well in a spotting tile. Put 4 cm3 of 1 % protein solution into a boiling tube. Put 4 cm3 of pepsin solution into a second boiling tube. Put both boiling tubes into a water bath at 20 °C. After 4 minutes add the pepsin solution to the protein solution together in one boiling tube, mixing together with a stirring rod. After 20 seconds add a drop of the protein/pepsin mixture to a drop of biuret solution in one well of the spotting tile. Repeat step 6 until the biuret solution no longer changes colour. Repeat steps 1–7 at 10 °C (using an ice water bath), 30 °C, 40 °C and 50 °C. The concentration of protein present in the solution can also be measured using a colorimeter. In a colorimeter, the amount of light that cannot pass through a solution is measured; giving the ‘absorbance’ of a solution. The darker the colour, the higher the absorbance. Suggest advantages of using the colorimeter method rather than the method used by the students. (2 marks) (b) The graph below shows a calibration curve of concentration of protein versus © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 39  absorbance. An experiment was carried out to investigate the effect of a protease enzyme on a 1 % protein solution. The absorbance at 30 °C was 0.8 arbitrary units after 20 seconds.Using the calibration curve, estimate the final concentration of protein in this solution after 20 seconds. (1 mark) (c) Explain why the concentration of protein in the solution at 10 °C after 1 minute is different from the concentration at 30 °C after 1 minute in the graph in part (b). © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 40  (2 marks) (d) The student repeated the experiment but incubated the protease and 1% protein solution at 80 °C. The absorbance was measured at approximately 1.14 arbitrary units. Suggest a reason for this result. (2 marks) © 2024 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 41