Anaerobic respiration
Some organisms live and reproduce in oxygen-poor or oxygen-deficient environments. These types of organisms also need ATP to sustain life. To obtain the required energy they undergo anaerobic respiration.
Anaerobic respiration is a process that produces ATP in the absence of oxygen and is often called anaerobic fermentation.
Anaerobic fermentation is most common in bacteria like E.coli or Salmonella.
Anaerobic fermentation can also occur in strains of yeast, a unicellular fungus, and this type of fermentation is typically seen in alcohol production or cooking processes. This type of fermentation is called alcoholic fermentation.
Human muscle cells can also carry out a special type of anaerobic fermentation in times of extreme exercise or when bursts of power are required to perform an activity more quickly than oxygen can be delivered to the cells. This process produces lactic acid as a by-product and is known as lactic acid fermentation.
Whilst the overall yield of ATP per glucose molecule is less than aerobic respiration, the speed at which ATP is produced is quicker.
Use this page to revise the following concepts within anaerobic respiration:
- Anaerobic respiration in animals
- Anaerobic respiration in yeasts
- Summary of anaerobic fermentation
- Compare and contrast between aerobic and anaerobic respiration
Anaerobic respiration in animals
During high intensity muscle use or explosive bursts of energy, animals that require quick energy in large amounts rely on anaerobic respiration to provide this level of energy.
Anaerobic respiration in animals is a metabolic process that occurs in the absence of oxygen, primarily to generate energy when oxygen is scarce, such as during intense exercise.
The equation for this process is: glucose → lactic acid
This process is used by 100m sprint runners, weightlifters, or the cheetah running after their prey.
| Anaerobic respiration inputs | Anaerobic respiration outputs |
|---|---|
Glucose ADP + Pi NAD+ | Lactic Acid 2 ATP NAD+ |
Click on the hotspots below to learn more about anaerobic fermentation in animals.
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Anaerobic respiration in yeasts
Anaerobic respiration in yeast and other microbes is a metabolic process that occurs in the absence of oxygen, allowing yeast cells to generate energy. This is also known as alcoholic fermentation.
During this process, glucose (or other sugars) is broken down to produce ATP.
The equation for this process is: glucose → ethanol + 2CO2
This process is important in industries such as brewing, winemaking, and baking, where the production of ethanol and carbon dioxide is desirable.
| Alcoholic fermentation inputs | Alcoholic fermentation outputs |
|---|---|
Glucose ADP + Pi NAD+ | Ethanol Carbon dioxide 2 ATP NAD+ |
Click on the hotspots below to learn more about anaerobic fermentation in yeast.
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Summary of anaerobic fermentation
Compare and contrast between aerobic and anaerobic respiration
Both aerobic and anaerobic respiration produce energy, but are used by different types of cells in different environmental conditions.
Use the following summary table to consolidate your understanding about the process of aerobic respiration and anaerobic respiration.
| Aerobic Respiration | Anaerobic Respiration | |
|---|---|---|
| Oxygen Supply | Plentiful supply of oxygen | Little / no oxygen supply |
| Who | Plants, animals, bacteria, fungi | Yeasts, some bacteria, at times animal muscle cells |
| Steps | Glycolysis Krebs Cycle Electron Transport Chain | Glycolysis |
| Inputs | Glucose Oxygen | Glucose |
| Outputs | Carbon dioxide Water | Lactic acid or Ethanol and carbon dioxide |
| ATP yield per molecule of glucose | 30 or 32 ATP | 2 ATP |
| Location | Cytoplasm Mitochondria | Cytoplasm |