2015 HCI H1 Biology Prelims P1 Questions

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4 © Hwa Chong Institution 2015 8875 H1 Biology / JC2 Preliminary Exams / Paper 1 3 The rate of reaction of a typical human enzyme was compared with the rate of reaction of a typical enzyme taken from bacteria that live in hot springs. The rates of reaction were measured over the same range of temperatures. The data obtained is shown in the following diagram. Which statement can be concluded? A Typical human enzymes fail to act at tem peratures above 50ºC as they are denatured due to disruption of covalent bonds. B The temperature coefficient for typical enzymes from bacteria that live in hot springs is two for temperatures between 45ºC to 75ºC. C A denatured human enzyme would resume activity if reincubated at 20ºC. D Enzymes from bacteria that live in hot springs withstand temperatures up to 90ºC as they have a low K m value. 4 Ethylene glycol is a chemical used to prevent water from freezing. If ethylene glycol is swallowed accidentally, it is metabolised by an enzyme found in liver cells to produce a toxic product. The enzyme normally catalyses the oxidation of ethanol to a harmless product. People who have swallowed ethylene glycol ar e treated with large doses of ethanol. This prevents formation of a toxic product and allows the body to excrete the ethylene glycol. Which statement describes why this treatment works? A Ethanol binds near the active site on the enzyme, altering its shape. B Ethanol dissolves the co-factor of the enzyme, making the enzyme non-functional. C Ethanol changes the tertiary structure of the enzyme, denaturing it. D Ethanol is more likely to bind to the active site on the enzyme. temperature / ºC rate of reaction / arbitrary units human bacteria 100 80 60 40 20 0

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