Question

Refer to the given graph showing relationship between temperature and enzyme action.

Select the correct statement regarding 'A' and 'B'.
(i). 'A' shows rate at which reaction decreases due to denaturation of enzyme molecules.
(ii) 'B' shows rate at which reaction increases due to decreased kinetic energy of substrate. (iii) As temperature rises, more and more enzyme molecules are denatured and 'A' appears to fall.
(iv) 'B' shows rate at which reaction increases due to increased kinetic energy of substrate and enzyme molecules.

• A. (i), (iii) and (iv)
• B. (iii) only
• C. (iii) and (iv) only
• D. (i) and (ii) only

Answer 1

Answer: (A)

In this study, enzyme and substrate are treated with increasing temperature before they are mixed, and the rate of reaction is determined. Enzymes are mostly proteinaceous molecules. Proteins are denatured by heat, and the rate of denaturation increases and becomes significant at higher temperatures. When enzyme is mixed with substrate, with increase in temperature the rate of reaction increases as there is increased kinetic energy of both substrate and enzyme molecules leading to more rapid movement and their collisions, Flowever, with increase in temperature denaturation of enzyme occurs which is an irreversible destruction; eventually destroying the active sites. As a result there is an apparent optimum temperature for the action of an enzyme due to dual effects, firstly, on the reaction and secondly, the stability of the enzyme protein.