12.2.2

Anaerobic Respiration

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Anaerobic Respiration

The end product of glycolysis is pyruvate and this can then be used in aerobic or anaerobic respiration. There are two types of anaerobic respiration: ethanol fermentation and lactate fermentation.

Illustrative background for Ethanol fermentationIllustrative background for Ethanol fermentation ?? "content

Ethanol fermentation

  • Ethanol fermentation is the conversion of pyruvate to ethanol under anaerobic conditions.
  • This process only takes place in plants and yeast.
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Pyruvate → ethanol

  • Pyruvate is first converted to ethanal by the enzyme pyruvate decarboxylase.
    • CO2 is produced as a by-product.
  • Ethanal is then reduced to ethanol.
    • This reaction is catalysed by ethanol dehydrogenase.
    • NADH is oxidised to NAD.
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Rice

  • Rice plants grow with their roots submerged in water. Their roots depend on ethanol fermentation to get a lot of their energy.
  • The roots of rice plants are able to withstand high levels of ethanol.
  • Rice stems also contain aerenchyma tissue.
    • This is a spongy tissue that allows easy, low-resistance gas exchange between the above water and submerged parts of the plant.
  • This allows the roots to get access to some oxygen even though they are submerged.
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Lactate fermentation

  • Lactate fermentation is the conversion of pyruvate to lactate.
  • This process takes place in animals and some bacteria. It is common in skeletal muscle when there is an insufficient oxygen supply, such as during exercise.
  • The lactate is converted back to pyruvate when there is sufficient oxygen present.
    • The amount of oxygen required after exercise to do this is called an "oxygen debt".
Illustrative background for Pyruvate → lactateIllustrative background for Pyruvate → lactate ?? "content

Pyruvate → lactate

  • Pyruvate is reduced to lactate.
    • This reaction is catalysed by lactate dehydrogenase.
    • NADH is oxidised to NAD.

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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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