14.1.1

Homeostasis

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Homeostasis

Homeostasis is the maintenance of the internal environment within an optimum range. Homeostasis is necessary to control the following factors:

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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).
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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.
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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).
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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.
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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.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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