Question

1. What are compatible solutes, and when and why are they needed by the cell?
2. What is the compatible solute of Halobacterium?
3. How does superoxide dismutase or superoxide reductase protect a cell?

Answer 1

A compatible solute is a small molecule having osmotic properties and act as osmolytes that help the cell to balance external osmotic pressure and cell volume. These solutes can be accumulated from surrounding or can be synthesized within the cells. These compatible solutes play an important role in the proper functioning and structures of proteins. Examples of these types of solutes are betaines, amino acids, trehalose(Sugar).

Halobacterium needs a halo or saline environment to maintain its equilibrium. The compatible solutes help to maintain the salt balance in the halophiles by incorporating surrounding salts into the cell. Some types of compatible solutes include glycerol, sugar derivatives, amino acid derivatives, and quaternary amines such as glycine betaine and ectoine.

Superoxide dismutase(SOD) is an enzyme that helps in the catalysis of superoxide radicals in normal molecular oxygen.

-O2    H2O2 + O2

The superoxide radical in highly reactive in nature and also highly potent oxidising agent. This can rapidly oxidise various cellular components like lipids, nucleic acids, proteins and destabilise their structures. They also attack hydrogen atom to generate another destructive hydroxyl radical. Hence the SOD helps to catalyse superoxide radicals to normal molecular oxygen and hydrogen peroxide.