Question

“Lock and key” model of enzyme action illustrates that a particular enzyme molecule
A. Is destroyed and resynthesized several times
B. Reacts at the same rate in all conditions
C. Interacts with the specific type of substrate molecules
D. Forms a permanent enzyme- substrate complex

Answer 1

Enzymes are the biocatalyst. Just as the lock has only one key, the enzyme also works in the same manner where enzymes act as the lock for the substrate which acts as a key.

Complete Answer:
Enzymes are catalysts which are proteinaceous in nature. They mainly accelerate the biochemical reaction. The rate of enzymatic reaction is affected by various factors such as-
- pH
- Temperature
- Concentration of substrate

The optimum range at which the enzyme works best is 25 to 38 degree Celsius. Increase or decrease in temperature from optimum level leads to inactivity of enzyme. Similar works for the pH as well. At optimum pH, they are active whereas at high/ low pH they became inactive.
Substrate: It is the molecule which acts with the enzyme to form a product. It gets attached to the active site of an enzyme. There are various models of enzyme action such as lock and key model, induced fit hypothesis, conformational selection model.

Lock and key model: Given by Emill fischer in 1894.
- One of the popular models for enzyme action.
- The theory is based on the shapes of enzymes and substrates.
- The shape of substrate is such that it gets fit into the active site of enzyme, enzymes represent the lock and the substrate acts as the key which after fitting causes activation of the enzyme.
- After the substrate gets attached to the enzyme, the enzyme molecule gets activated and is not destroyed and re-synthesized. The enzyme works differently in different conditions and thus affects the rate of reaction differently. The enzyme substrate complex thus formed is a temporary transient complex as it has to form the product and free the enzyme for the second round of action.

So, the correct answer is option (C).

Note: The enzymes are catalysts which itself do not take part in the reaction. They help the reaction to proceed by affecting its rate of reaction. The lock and key hypothesis state the lock which is the enzyme has a fixed shape for the complementary key which is the substrate. This enzyme substrate complex leads to the production of product after its reaction.