Production of Ketone Bodies Flashcards
What is the key intermediate between fat and carbohydrate metabolism
Acetyl-Coa
Where does ketogenesis take place
Mitochondrial matrix in the liver
When does ketogenesis take place
When blood glucose levels are low and other carbohydrate stores (glycogen) have been exhausted
Why does ketogenesis cause a decrease in oxaloacetate
Low levels of oxaloacetate reduces the efficiency of the TCA cycle causing acetyl-CoA levels, coming from the β-oxidation of lipids, to rise. Therefore, gluconeogenesis cannot be done because low oxaloacetate, so TCA cycle also has no intermediates because no oxaloacetate so instead acetyl coa in high concentrations is used to produce ketone bodies
What 2 ketone bodies is acetyl-CoA converted to?
- Acetoacetate
- β-hydroxybutyrate
Producing Ketone bodies Step 1
1st condensation – reversal of the last step of β-oxidation
Producing Ketone Bodies Step 2
Condensation of Acetoacetyl-CoA with an extra acetyl CoA
Producing Ketone Bodies Step 3
Release of acetoacetate
Producing Ketone Bodies Step 4a
Reduction of acetoacetate to form β-hydroxybutyrate by D- β-hydroxybutyrate dehydrogenase
Producing Ketone Bodies Step 4b
Spontaneous decarboxylation of acetoacetate to acetone (or by the action of acetoacetate decarboxylate)
What is the role of ketone bodies during fasting and starvation
During fasting and starvation, acetoacetate and β -hydroxybutyrate are generated in the liver where peripheral tissues can utilize these molecules as an alternative fuel under ketogenic conditions.
In summary, the liver is in charge of the production of ketone bodies whereas peripheral tissues (mainly the brain) will consume these alternative fuels.
Can the liver consume ketone bodies?
No, it produces ketone bodies. It cant use ketone bodies because it does not contain beta-ketoacyl-CoA transferase, so it cant produce acetyl-CoA from ketones
Ketone body production and diabetes
Liver does not know there is no glucose and will do gluconeogenesis on a constant basis. Will use Amino acids and fatty acids to produce glucose so lose weight because you break down proteins to try and produce glucose even though there is plenty of it because it cannot detect it.
