Homeostasis
Biology: Cambridge International A Level, topic 14.1.1
Homeostasis
Homeostasis is the maintenance of the internal environment within an optimum range. Homeostasis is necessary to control the following factors:
High temperature
- Homeostasis maintains optimum core body temperature. This is approximately 37°C in humans.
- If body temperature rises above the optimum range, enzymes denature.
- The higher temperature causes the hydrogen bonds that maintain the enzyme structure to break.
- This alters the enzyme active site so the enzyme can no longer catalyse reactions (e.g. respiration).
Low temperature
- If temperature falls below the optimum range, enzyme activity declines.
- Decreased enzyme activity causes the rate of important reactions (e.g. respiration) to slow down.
Blood pH
- Homeostasis maintains blood pH.
- If blood pH rises above (too alkaline) or falls below (too acidic) the optimum range, enzymes denature.
- Denatured enzymes can no longer catalyse important reactions.
- Optimum pH range is normally around pH 7. Some enzymes have very different optimum ranges (e.g. enzymes in the stomach have a very acidic optimum pH).
High blood glucose
- Homeostasis maintains blood glucose concentration.
- If blood glucose levels rise above the optimum range, the water potential of the blood is reduced.
- Low water potential in the blood causes water to diffuse out of the cells by osmosis and into the blood.
- This makes the cells flaccid and they die.
Low blood glucose
- Homeostasis maintains blood glucose concentration.
- If blood glucose levels fall below the optimum range, there is not sufficient glucose for respiration.
- Respiration rate declines and energy levels fall.
Test yourself on Homeostasis
If our internal conditions are not regulated, which of the following could denature?
Which of the following statements about homeostasis are true?
Which of these is NOT an example of homeostasis?