Enzymes are biological catalysts. They accelerate biological reactions. Which of the following is not true about enzymes?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Enzymes accelerate biological reactions by increasing the energy of activation.
Like any catalyst, an enzyme speeds up a reaction by providing an alternative pathway of lower activation energy. More molecules then have enough energy to react. For example, the activation energy for the hydrolysis of sucrose is 6.22 kJ mol−1 with acid, but only 2.15 kJ mol−1 with the enzyme sucrase.
Option (1) They are globular proteins. — True about enzymes. Almost all enzymes are globular proteins, folded into a compact shape with an active site that fits a particular substrate.
Option (2) They are required in small quantities. — True about enzymes. An enzyme is not used up, so a small amount converts a large amount of substrate.
Option (3) The names of all enzymes ends with the suffix-ase. — True about enzymes. Enzymes are named after their substrate or their reaction with the ending –ase, such as maltase (for maltose) and oxidoreductase.
Option (4) Enzymes accelerate biological reactions by increasing the energy of activation. — Not true about enzymes. An enzyme lowers the activation energy; raising it would slow the reaction down.
NCERT (2026-27 edition):
Enzymes – “… Almost all the enzymes are globular proteins. Enzymes are very specific for a particular reaction and for a particular substrate. They are generally named after the compound or class of compounds upon which they work. … The ending of the name of an enzyme is -ase.”
Mechanism of Enzyme Action – “Enzymes are needed only in small quantities for the progress of a reaction. Similar to the action of chemical catalysts, enzymes are said to reduce the magnitude of activation energy.”