Biology > QUESTION PAPER (QP) > TSSM BIOLOGY 2019 Unit 3 Key Topic Test 4 – Structure and regulation of Biochemical pathways QUEST (All)

TSSM BIOLOGY 2019 Unit 3 Key Topic Test 4 – Structure and regulation of Biochemical pathways QUESTION BOOK

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An enzyme is known as a protein catalyst. This means enzymes A. cause chemical reactions to be slowed down by decreasing activation energy B. cause the rate of chemical reactions to increase due to ... increasing activation energy C. lower activation energy of a chemical reaction increasing the rate of reaction D. have an active site which must have cofactors attached to decrease activation energy Question 2 As part of a chemical reaction, enzymes A. increase the rate of the chemical reaction by breaking bonds between the amino acids in the enzyme B. are used up as part of the reaction and need to be remade by transcription and translation C. are permanently altered when the enzyme active site is used by the substrate D. are not consumed in a reaction and may be used in further reactions Question 3 Refer to the graph above. In this reaction A. the products have a lower activation energy than the substrates B. bonds have been formed to synthesise the product C. the reactant has been broken into smaller products D. the enzyme has not reduced the activation energy 2019 BIOLOGY KEY TOPIC TEST  TSSM 2019 Page 4 of 11 Question 4 A student conducted an experiment where the enzyme catalase was added to hydrogen peroxide (H2O2). The student noticed a gas was released from the aqueous solution and that the test tube became warm. This is an example of A. a catabolic reaction as the reaction releases a gas B. an anabolic reaction as the reaction causes heat to be released C. a catabolic reaction as energy is used to build the products D. a catabolic reaction as hydrogen peroxide is broken into hydrogen and oxygen. Question 5 A student conducted another experiment using the protein in egg white as the substrate and protease as the enzyme. At the start of the experiment the egg white was translucent but after the protease was added the egg white became a clear liquid. This is because A. the reaction is anabolic, and the products are less complex, so they are clearer B. protease breaks the protein in egg white into protein monomers which are smaller C. protease turns egg white protein into water making the liquid clear D. protease causes the egg white to undergo hydrolysis reactions releasing water Question 6 Proteins have a specific three-dimensional shape formed when amino acids form bonds. Enzymes have an area called the active site which may fit a substrate in a lock and key or induced fit model. The induced fit model infers that A. the active site only fits one specific substrate without changing shape B. the substrate will change shape to help the active site fit C. the substrate plays a role in determining the final shape of the enzyme D. the enzyme is flexible and breaks bonds between amino acids to fit the substrate Question 7 Penicillin acts as an irreversible inhibitor of the enzyme transpeptidase active site. Transpeptidase is used by bacteria to catalyse the building of bacterial cell walls by cross linking peptidoglycan. This means that penicillin A. stays attached to the transpeptidase active site preventing crosslinking B. leaves the enzymes active site once the bacterial wall is built C. changes the shape of the active site to fit peptidoglycan D. kills bacteria by competing for peptidoglycans active site 2019 BIOLOGY KEY TOPIC TEST  TSSM 2019 Page 5 of 11 Question 8 Cyanide acts as a non-competitive inhibitor to the enzyme cytochrome c oxidase. It prevents the electron transport chain from working by stopping the enzymes ability to transfer hydrogen ions across the inner mitochondrial membrane. This means that A. cyanide enters the active site of cytochrome c oxidase B. cyanide alters the shape of cytochrome c oxidases active site C. cyanide poisoning is irreversible D. hydrogen ions attach to the cyanide in preference to the enzyme Question 9 Statins are examples of competitive inhibitors that block the active site of enzyme HMG-CoA reductase so that it cannot convert HMG-CoA which is a substrate in the pathway for cholesterol production in the liver. Statins are used as a medical intervention to reduce cholesterol in the blood, therefore statins A. become less effective if HMG-CoA levels are increased B. become more effective as cholesterol levels increase C. compete with Cholesterol for the active site of HMG-CoA reductase D. cannot be removed from the active site of the enzyme once they are attached Question 10 A student was exploring the link between enzyme activity and temperature. Amylase was used to digest starch at different temperatures and the results were recorded. Once the experiment was completed a graph was produced showing the graph below: Considering these results which of the following statements is correct? A. Enzymes die if the temperature goes above the optimum B. Enzymes slowly denature if the temperature drops below the optimum C. The enzymes optimal temperature is where the most substrate is being changed D. Enzymes are still being digested above and below the optimal temperature 2019 BIOLOGY KEY TOPIC TEST  TSSM 2019 Page 6 of 11 Question 11 A scientist was comparing pH levels in different parts of the human digestive system and the effect of pH on enzyme activity. The results of the investigation are graphed below When considering the results shown in the graph above which of the following inferences is correct? A. Pepsin, amylase and arginase would all work in the mouth B. All the enzymes have an optimal pH of 7 C. Arginase would never denature as the pH does not get high enough D. Pepsin has a narrower effective pH range that amylase or arginase Question 12 Trypsin is a protease enzyme found in the small intestine and produced in the pancreas that breaks down the protein casein that makes milk cloudy. As the concentration of casein increases the rate of reaction increases until the saturation point where the rate levels off. The limiting factor in this case is A. the limited amount of amino acids in the small intestines B. the surface area of the trypsin enzyme C. number of available trypsin active sites D. the amount of available casein protein. Question 13 ATP, NADH and NADPH are known as loaded forms of coenzymes that take part in reactions in organisms. In this context loaded means A. carrying energy, protons or electrons between reactions B. carrying hydrogen C. being part of photosynthesis and respiration D. the ability to carry molecules into the electron transport chain and light dependent reactions 2019 BIOLOGY KEY TOPIC TEST  TSSM 2019 Page 7 of 11 Question 14 The unloaded forms of ATP, NADH and NADPH are A. ADP + Pi, NAD+ and FAD B. energy, hydrogen ions and electrons C. ADP, NAD and NADP D. inorganic phosphate and hydrogen Question 15 Cofactors and coenzymes are both essential for biological activity of enzymes. The molecules work in different ways to enhance enzyme activity. The correct way to classify them is that A. coenzymes are inorganic, and cofactors are organic B. cofactors remove electrons from substrates and pass them onto other molecules C. both cofactors and coenzymes bind to the enzyme to configure the active site D. inorganic cofactors act as carrier molecules while coenzymes participate in catalysis 2019 BIOLOGY KEY TOPIC TEST  TSSM 2019 Page 8 of 11 SECTION B - Short-answer questions Instructions for Section B Answer all questions in the space provided. Write using a blue or black pen. Question 1 Organisms use a range of enzymes to catalyse a variety of chemical reactions. Enzymes act within a strict range of conditions including temperature and pH. a. Enzymes are proteins that have a specific 3D shape that is produced through the interaction and bonding of amino acids R groups. A critical part of this shape is the enzyme’s active site where chemical reactions occur. There are two hypotheses about how substrates fit into the active site. Name the two theories and explain the difference between the two with reference to the active site _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ b. Enzymes catalyse chemical reactions by lowering activation energy. What does activation energy refer to in a biological sense? _____________________________________________________________________ _____________________________________________________________________ c. Enzymes catalyse catabolic or anabolic reactions which either break or build bonds respectively. For both catabolic and anabolic reactions give the energy levels of the products compared to the energy level of the substrate and explain why energy levels change _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ 4 + 1 + 4 = 9 marks 2019 BIOLOGY KEY TOPIC TEST  TSSM 2019 Page 9 of 11 The active site of an enzyme fits a specific substrate due to its specific shape. However, enzymes can be inhibited through the action of molecules which have an affinity with the active site. d. Inhibitors can be either competitive or non-competitive. Compare the two types of inhibitor referring to substrates in your answer. _____________________________________________________________________ _____________________________________________________________________ e. Heavy metals such as lead and mercury are known to be poisonous. This is because these metals are irreversible non-competitive inhibitors of enzymes such as catalase, amylase, lipase, and lactase. Explain why treatment for heavy metal poisoning is difficult. _____________________________________________________________________ _____________________________________________________________________ f. Draw, using two separate diagrams, non-competitive and competitive inhibition of an enzyme. Use the same substrate shape for each diagram. 4 + 2 + 4 = 10 marks 2019 BIOLOGY KEY TOPIC TEST  TSSM 2019 Page 10 of 11 Question 2 Enzyme based reactions are affected by a range of factors that affect the interaction of the substrate with the active site of the enzyme. If enzymes are exposed to conditions outside of the optimal range the enzyme may denature. a. Define the term denature. _____________________________________________________________________ _____________________________________________________________________ b. Hypothermia and hyperthermia are conditions that lead to low body temperature and high body temperature respectively. Whilst humans can survive a low body temperature of up to 15 degrees below optimal, a body temperature of 5 degrees above optimal is deadly. Explain this difference in effect with reference to enzymes in hypothermia and hyperthermia. _____________________________________________________________________ _____________________________________________________________________ ____________________________________________________________________ _____________________________________________________________________ c. As enzyme concentration increases the rate of reaction increases as well. Explain why this occurs. _____________________________________________________________________ _____________________________________________________________________ 1 + 4 + 2 = 7 marks 2019 BIOLOGY KEY TOPIC TEST  TSSM 2019 Page 11 of 11 Question 3 Coenzymes act as carrier molecules for various reactions in cells. a. Cells cycle coenzymes to transfer energy, protons or electrons. Give an example of a loaded and unloaded coenzyme that transfers energy. _____________________________________________________________________ _____________________________________________________________________ b. Many coenzymes are organic vitamins which attach to an enzyme and interact with the enzymes active site to enhance interaction with a substrate. Why must we continually ingest some vitamins through our food? _____________________________________________________________________ _____________________________________________________________________ c. Which of the structures is the coenzyme (A, B, C or D) in the following diagram? [Show More]

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