IGCSE Biology Paper-4: Specimen Questions with Answers 275 - 277 of 279

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Question 275

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Explain how regular brushing helps to prevent tooth decay.

Explanation

Regular tooth brushing helps to prevent tooth decay and gum disease by reducing the number of bacteria and plaque around the teeth and gums.

Passage

Table shows the enzyme activity of alcohol dehydrogenase at different temperatures.

The Enzyme Activity of Alcohol Dehydrogenase at Different Temperatures
temperature / °Cenzyme activity/arbitrary units
32120
43170

Question 276 (1 of 2 Based on Passage)

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State one factor, other than temperature, that affects enzyme activity.

Explanation

Factors Affecting the Enzyme Activity

Hydrogen ion concentration (pH) : Some enzyme act best in an acid medium, other in an alkaline medium, for every enzyme there is an optimum pH where its action is maximum e. g. , 2 for pepsin, for salivary amylase, for trypsin. Most enzyme show maximum activity in a pH range of about i.e.. , near neutral pH (endoenzymes) .

PH of Enzyme

Question 277 (2 of 2 Based on Passage)

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The information in Table shows that an increase in temperature increases the activity of alcohol dehydrogenase.

Explain why an increase in temperature causes an increase in enzyme activity.

Explanation

Temperature

Within certain limits the rate of an enzyme catalyzed reaction increases as the temperature increases. The of most enzymatic reactions is 2, i.e.. , every rise in temperature doubles the rate of reaction. Most enzymes show maximum activity in a temperature range of . Beyond this temperature, enzymes become denatured but the enzymes are not destroyed by freezing, and regain their lost activity if the temperature is raised to normal.

Optimum Temperature

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