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Ch 5Metabolism and enzymesSuggested answersCh 5Metabolism and enzymesThink about…(Ch 5, p.2)1.Enzymes are proteins that act as biological catalysts to speed up metabolic reactions.2.Enzymes catalyse the breakdown of cellulose fibres of the jeans so that the jeans becomesoft.3.This reduces the overall cost of stonewashing, such as water, electricity, wages etc.Quick Practice(Ch 5, p.9)A(3) is incorrect. The active site of an enzyme has a specificshape. Only the substrate that fits exactly into the active sitecan bind to the enzyme.Quick Practice(Ch 5, p.21)1.DA is incorrect. Most enzymes are inactive, but not denatured, at 0 oC.B is incorrect. 37 oC is the body temperature of humans but the optimum temperature of most human enzymes is 40 to 45 oC rather than 37 oC.C is incorrect. Enzymes are not living thing. They are denatured, rather than killed, by high temperatures.2.DHigh temperatures, extreme pHs and inhibitors that bind permanently to the enzymes cancause the active sites of enzymes to change shape, so that the active sites no longer fit thesubstrates.Quick Practice(Ch 5, p.28)AEnzyme P works well in moderate temperatures which do not cause damage to the clothes. It can tolerate in a slightly alkaline medium of the detergent.B is incorrect. Enzyme Q works well only in high temperatures, which can cause damage to the clothes.C is incorrect. Enzyme R works well only in acidic medium, while the washing powder solution is alkaline.D is incorrect. Enzyme S works well only in extremely high temperatures, which can cause damage to the clothes.1
Ch 5Metabolism and enzymesSuggested answersSection exercise(Ch 5, p.31)1.(a)catabolism(b)anabolism(c)respiration(d)photosynthesis2.T3.F4.T5.F6.F7.T8.F9.F10.(a)The activation energy of the reaction catalysed by enzymes is lower than the uncatalysed reaction.(b)It is because enzymes speed up chemical reactions taking place in an organism.11.(a)C:enzymeD:productX:enzyme-substrate complex(b)lock-and-key hypothesis(c)Both the active site of the enzyme and the key have a specific shape. In order to open a lock, the key with a specific shape must fit into the lock. Similarly, each enzyme can act only on substrates that fit into its active site.(d)formation of protein or starch12.BThe enzyme is denatured upon heating. It loses its activity permanently.13.C14.D15.(a)protease(b)pectinase(c)cellulose(d)protease and amylase2
Ch 5Metabolism and enzymesSuggested answersRevision exercise(Ch 5, p.33)1.AThe graph represents an anabolic process as the higher energy level of product indicates an increased energy level, i.e. energy is absorbed during the reaction.2.BThe activation energy of the reaction catalysed by the enzyme is lower than the uncatalysed reaction. The energy levels of products are the same in catalysed and uncatalysed reactions.