Activity of an enzyme is least affected by:

Question

Accepted Answer

The correct option is 4:
The original activation energy of the system is the energy barrier that needs to be overcome for a reaction to proceed in the absence of an enzyme. Enzymes, as biological catalysts, function by lowering this activation energy, thereby speeding up the reaction. However, the *original* activation energy itself is an intrinsic property of the reaction without the enzyme and is not a variable that directly "affects" the enzyme's activity in terms of its efficiency or rate once the enzyme is present. Enzymes influence the activation energy, but their activity is not determined by the initial, uncatalyzed activation energy of the system.

The incorrect option is 1: Temperature.
Temperature significantly affects enzyme activity. There is an optimal temperature at which an enzyme functions most efficiently. Both excessively low and high temperatures can decrease enzyme activity; low temperatures slow down molecular motion, while high temperatures can cause denaturation, irreversibly altering the enzyme's active site.

The incorrect option is 2: Concentration of substrate.
The concentration of the substrate directly impacts the rate of an enzyme-catalyzed reaction. As substrate concentration increases, more active sites on the enzyme become occupied, leading to an increased reaction rate, up to a saturation point where all active sites are continuously bound.

The incorrect option is 3: Concentration of enzyme.
The concentration of the enzyme also directly influences the reaction rate. With an increase in enzyme concentration, there are more available active sites to bind with the substrate, which in turn leads to a faster conversion of substrate into product, assuming there is sufficient substrate.