Ketogenesis is the formation of ketone bodies in the liver mitochondria when fatty acid breakdown from beta-oxidation exceeds carbohydrate breakdown, such as during starvation or uncontrolled diabetes. This is because acetyl-CoA production overloads the citric acid cycle. Acetyl-CoA is converted to ketone bodies like acetoacetate, acetone, and 3-hydroxybutyrate, which travel through the bloodstream and are used by muscles and brain as fuel, providing an easy transport of fatty acid energy when glucose is limited.

1. Ketogenesis (Formation of Ketone bodies)
• When beta-oxidation exceeds carbohydrate
breakdown (e.g. during starvation and
uncontrolled diabetes) ketone bodies are
produced by liver mitochondria, which is called
ketogenesis
• This is because the large amount of acetyl CoA
produced by beta oxidation overloads the citric
acid cycle (limited carbohydrate means that TCA
cycle intermediates will be depleted - not
enough oxaloacetate to condense with all that
acetyl CoA).

2. • Instead, acetyl CoA is converted to ketone
bodies which are given as:
– Acetoacetate
– acetone
– 3-hydroxybutarate

3. • Ketone bodies travel from the liver to blood
and muscle where they are converted back to
acetyl CoA and enter the citric acid cycle.
• In starvation the brain can also use ketone
bodies as a fuel.

4. • Ketone bodies are an easy way of
transporting the energy stored in fat from
the liver to the other tissues because they
are soluble in the blood
– the acetone comes from spontaneous
decomposition of acetoacetate in the blood and
can be sensed in the breath

5. • Utilization of ketone bodies is called ketolysis

7. ketogenesis
ketolysis