NSS Mastering Biology Suggested Answer Book 1A (P.4-22)

10 a The rate of reaction increases when the polyphenol oxidase concentration increases. 1m b Rate of reaction = 1/18 = 0.056 1m From the graph, the enzyme concentration is around 1.15%. 1m c Use boiled enzyme in the tube. 1m d The enzyme does not work in acidic medium. / The enzyme is denatured in acidic medium. 1m e The colour change becomes faster at start 0.5m as enzyme activity increases with temperature. 0.5m When temperature becomes too high, no further colour change will be observed 0.5m as the enzyme is denatured. 0.5m f The rate of reaction drops / stops if all active sites of the enzymes are blocked. 1m The inhibitor competes with normal substrate for active sites. 1m 11 HKCEE Biology 2003 I Q3b Essay (p. 4-23) 12 Enzymes are biological catalysts, speeding up metabolic reactions without being used. 1m Enzymes can be reused. Enzyme molecules return to its original form after completing the reaction. 1m Enzymes are required in relatively small amount because enzymes remain unchanged in the reaction. 1m Enzymes are proteins. They are easily denatured by high temperatures and extreme values of pH. 1m The actions of enzymes are specific. Each enzyme catalyses only one type of reaction. 1m Examples of enzyme application: Biological washing powder, papain in meat tenderizers, enzyme to coagulate milk to produce cheese, enzyme to modify the starch in bread, enzymes to break down plant cell wall in fruit juices, enzymes to remove hairs from hides 1m Advantages of using enzymes in the above applications: Enzymes are specific in action. This reduces the production of unwanted products. 1m Enzymes are efficient in small amounts. This lowers the cost of production. 1m