Answer the question on the basis of passage given below:
A colloid is a heterogeneous system in which a substance is dispersed (dispersed phase) as fine particles in another substance called dispersion medium. Their particle size is intermediate between that of pure solutions (<1 nm) and suspension (>1000 nm).
They are known for interesting properties such as enormous surface area, Tyndall effect, Brownian Motion etc. They are widely used in industries and day to day life. Some prominent uses of colloids are those in smoke precipitators, purification of water, medicines, cleansers etc.
Which of the following is true for enzyme catalytic reaction?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Its activity is maximum at 298-310K
Enzymes are protein catalysts, and every enzyme works best at a particular temperature, its optimum temperature. On either side of it the activity falls: at lower temperature the reaction slows down, and at higher temperature the protein starts to lose its structure (denaturation). For enzymes the optimum range is 298–310 K; human body temperature, 310 K, lies in it.
Why the other options are incorrect
Option (1) It increases with increase in temperature. — Incorrect. This holds only up to the optimum temperature; above it the enzyme is denatured and its activity drops.
Option (2) It decreases with decrease in temperature. — Incorrect. This is true only below the optimum; above the optimum, lowering the temperature towards 310 K increases the activity, so the statement is not true in general.
Option (4) Its activity is maximum at pH 8.5. — Incorrect. Enzymes work best at an optimum pH between 5 and 7, not at 8.5.
NCERT (Pre-rationalised edition, 2022-23):
Characteristics of Enzyme Catalysis – “… (iii) Highly active under optimum temperature: The rate of an enzyme reaction becomes maximum at a definite temperature, called the optimum temperature. On either side of the optimum temperature, the enzyme activity decreases. The optimum temperature range for enzymatic activity is 298-310K.”