Thermoregulation and osmoregulationSpec 7.10B
In short
Thermoregulation is the control of body temperature at about 37°C, the optimum for most enzymes: too hot and enzymes are denatured, too cold and reactions are too slow. Osmoregulation is the control of the water content of the blood. If the blood is too dilute, water enters animal cells by osmosis and they swell; too concentrated, and they shrink.
Thermoregulation: the effect on enzyme activity
Thermoregulation is the control of body temperature. Core body temperature is kept at about 37°C, which is the optimum temperature for most enzymes in the body.
- If the temperature rises too far, enzymes are denatured. The shape of the active site changes, so the substrate no longer fits and the reaction stops.
- If the temperature falls too far, enzymes work more slowly, so reactions in cells are too slow.
Osmoregulation: the effect on animal cells
Osmoregulation is the control of the water content of the blood. Animal cells have no cell wall, so water moving by osmosis changes them.
| Blood water content | Effect on animal cells |
|---|---|
| Too high (blood too dilute) | Water enters the cells by osmosis. The cells swell and may burst |
| Too low (blood too concentrated) | Water leaves the cells by osmosis. The cells shrink |
Say enzymes are denatured, not ‘killed’. Enzymes are proteins, not living things.
Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026