Limits of Heat Tolerance

The living organisms can normally survive only within a certain range of temperature of about 0-45°C. However, organisms tend to make adjustments, if they happen to be at places of higher or lower temperature.

Above 45°C, the organisms may suffer in many ways:

  • the enzymes are destroyed
  • proteins get denatured
  • plasma membrane breaks down
  • cells suffer lack of oxygen

Below 0°C

At temperatures below freezing point, the cells may burst by the formation of needle-like ice crystals inside and between the cells and the organisms cannot survive.

Efficiency of Enzymes at Different Temperatures

Enzymes carry out almost all the chemical reactions occurring inside our body. They have several characteristics and the most important one is their relation with respect to temperature.

At 0°C, the enzymes are inactive.

The rate of enzyme-catalyzed reactions doubles with every 10 degrees rise in temperature between 4-40°C.

On warming, whenever the temperature rises, the enzymes start working faster. If the temperature becomes too high (more than 40°C) the enzymes begin to work too rapidly and produce unwanted intermediate chemicals and not the required ones. At still higher temperatures the enzymes get denatured (destroyed).

The enzymes act best at a narrow temperature range, usually between 35-40°C.

On cooling, at temperatures lower than the optimum temperature the enzymes become less and less efficient. At freezing temperatures the enzymes may turn totally inactive.