IGCSE Biology Paper-1: Specimen Questions with Answers 152 - 152 of 208

Question 152

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Question

MCQ▾

Enzymes are affected by

Choices

Choice (4)
a.Activator/Inhibitor
b.pH
c.Temperature
d.All a. , b. and c. are correct

Answer

d.

Explanation

Factors Affecting Enzyme Function

  • Temperature: Enzyme functions optimally at certain temperature. As the temperature increases the kinetic energy also increases, molecules move faster, and it increases the chance of substrate colliding the enzyme’s active site and binding followed by reaction. But if the temperature is too high, the enzyme protein denatures (cools), thereby destroying the shape of active binding site (cannot bind to the substrate anymore) and decreasing the enzyme reaction rate.
  • pH (measure of acidity): Enzymes function optimally at certain pH and are certainly sensitive to the changes in the pH. Changes in the pH can make or break chemical bonds in the active binding site and thereby decreasing its effectiveness. If the pH is too high (acidic) or low (basic), the enzyme denatures. However, there are exceptions, digestive enzymes in the stomach function at pH of 3 - 4.
  • Concentration of the substrate: As the enzyme concentration increases, the rate of reaction also increases until a point when the amount of substrate available becomes limited. Similarly, when the substrate concentration is low, the rate of reaction is also slow.