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Which of the following is not true for enzymes? A Enzymes lower the activation energy barrier of a reaction. B Enzymes are made up of proteins. C Enzymes are used up in reactions. D Enzymes can be affected by changes in temperature. E Enzymes contain an active site.

Which of the following is not true for enzymes?

A

Enzymes lower the activation energy barrier of a reaction.

B

Enzymes are made up of proteins.

C

Enzymes are used up in reactions.

D

Enzymes can be affected by changes in temperature.

E

Enzymes contain an active site.

 

Grade:12

1 Answers

Omveer Singh
askIITians Faculty 52 Points
2 years ago

 

A. Enzymes alters the speed of a chemical reaction. When reactions proceed from one direction to another, enzymes have to overcome an energy barrier to activate the inactive molecule. The amount of energy required to raise the energy of molecule at which chemical reaction can occur is called activation energy. Enzymes lower the activation energy of a reaction. Hence statement A is correct.
B. Enzymes are water soluble colloidal macromolecules which are wholly or partially proteinaceous in nature. The protein part of enzyme is called apoenzyme while the non protein part is called prosthetic group which may be coenzyme or cofactor. Hence statement B is correct.
C. Each enzyme has a substrate binding site called the active site. Binding of the substrate to this site produces a highly reactive short lived complex called enzyme substrate complex which breaks up into chemical products and unchanged enzyme along with the intermediate formation of enzyme-product complex. So, enzyme is not used up in the reactions. Hence statement C is incorrect.
D. Enzymes function best at an optimum temperature 20-40°C . The enzyme activity decreases with slight decrease or increase from the optimum temperature range. At very high temperature, enzyme activity decreases because denaturation of proteins occurs and enzyme becomes inactive. Hence statement D is correct.
E. An enzyme has a distinct cavity or cleft in which substrate is bound. This cavity is known as active site which can hold a substrate molecule by its specific size, shape etc. Hence statement E is correct.
So, the correct answer is 'Enzymes are used up in reactions'.

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