Question

(I) Which one of the graphs show the effect of temperature on the velocity of a typical enzymatic reaction?

(II) Which one of the following graphs show the relationship between the rate of enzymatic activity and substrate concentraion (S)?

(correct answer + 2, wrong answer - 0.50)

• A. I - c
  II - d
  
• B. I - b
  II - d
  
• C. I - c
  II - c
  
• D. I - b
  II - a
  

Answer 1

The correct option is A I - c

II - d

(I) Enzymes work in a narrow range of temperature and have the highest activity at a particular temperature called optimum temperature.

At low temperature, the enzyme is inactive. Within the functional temperature range, the rate of an enzyme catalysed reaction increases with the increase in temperature. This is so because there would be excessive movement of the enzyme and the substrate which will ensure more collisions. Further increase in temperature will denature the enzyme and reduce the rate of the reaction. This is depicted by the graph c.

(II) When the concentration of the substrate is increased, more substrate molecules collide with the enzyme molecules and hence, more product is formed. The rate of reaction increases when the substrate concentration increases.

But this effect is valid upto a certain concentration called saturation poiny, beyond which the enzyme activity remains constant.

At a relatively low concentration of substrate, initial velocity (speed of reaction in a particular direction) increases linearly with an increase in a substrate concentration.

The reaction reaches a maximum velocity (Vmax) with an increase in the substrate concentration and it doesn’t increase any further by increasing the concentration of substrate. This is because the enzyme molecules are fewer than the substrate molecules and after saturation of these molecules, there are no free active sites available to bind with the additional substrate molecules.