Describe anaerobic metabolism and ketone production
Glycolysis (also known as the Embden-Meyerhof pathway):
- Describes the conversion of glucose to pyruvate (and two ATP)
- Does not consume O2 or produce CO2
Therefore it occurs in both anaerobic and aerobic conditions.
- Consumes two NAD+ and produces two NADH
In anaerobic conditions (in the erythrocyte, and in the setting of cellular hypoxia):
- There is no oxygen available to allow further ATP production via the electron transport chain
There is also no regeneration of NAD+ in the ETC.
- In order for glycolysis to continue, NAD+ is regenerated via production of lactate
About 1400mmol (20mmol/kg) of lactate is produced per day. Lactate is either:
- Oxidised in the cell
This requires restoration of NAD+, e.g. resolution of cellular hypoxia.
- Circulated to the liver
Lactate is then:
- Oxidised to pyruvate
- Converted to glucose via the Cori cycle
- β-oxidation of fatty acids in the liver produces acetyl-CoA
- Acetyl-CoA usually enters the citric acid cycle to produce ATP
When large amounts of acetyl CoA are produced, they may instead condense to form acetoacetate, which can then be reduced to β-hydroxybutyrate
These substances are known as ketones
Ketones can only be produced by the liver, and only used as a substrate by the kidney, as well as skeletal and cardiac muscle
- Production of ketones is accelerated by glucagon and adrenaline
- Kam P, Power I. Principles of Physiology for the Anaesthetist. 3rd Ed. Hodder Education. 2012.
- ANZCA August/September 2011