Why do enzymes show decreased activity at low temperatures?

Enzymes show decreased activity at low temperatures because the rate of molecular collisions decreases, slowing down the reaction.

Enzymes are biological catalysts that speed up chemical reactions in living organisms. They function by lowering the activation energy of a reaction, which is the energy required to initiate the reaction. Enzymes achieve this by providing an alternative reaction pathway with a lower activation energy. However, the rate at which enzymes catalyse reactions is heavily dependent on temperature.

At low temperatures, the kinetic energy of the molecules involved in the reaction is reduced. This means that the molecules move more slowly and collide less frequently. Since enzymes work by colliding with their substrate molecules, a decrease in the rate of molecular collisions leads to a slower reaction rate. Therefore, enzyme activity decreases at low temperatures.

Furthermore, enzymes are proteins, and their structure is crucial for their function. The structure of an enzyme is maintained by various types of bonds, including hydrogen bonds and disulphide bridges. At low temperatures, these bonds are not affected, and the enzyme maintains its shape. However, the reduced kinetic energy means that the enzyme and substrate molecules are less likely to collide in the correct orientation for a reaction to occur, further reducing the rate of reaction.

In summary, the decreased activity of enzymes at low temperatures can be attributed to the reduced kinetic energy of the molecules, leading to fewer collisions between enzyme and substrate molecules. This results in a slower reaction rate, hence lower enzyme activity.