Ketone bodies are water soluble molecules that contain the ketone groups produced from fatty acids by the liver.

1. Ketone Bodies
Smt.P.Sangeetha,
Lec. In Biotechnology,
KVRGCW(A),Kurnool.

2. Ketone bodies
 Ketone bodies are produced from Acetyl CoA mainly in the mitochondrial
matrix of the liver cell when carbohydrates are so scarce(fasting state)
that energy must be obtained from breaking down fattyacids.
 There are three water soluble compounds[Ketone bodies] that are
produced as byproducts when fatty acids are broken down for energy in
the liver and kidney.
 They are used as source of energy in the heart and brain.

3. Ketone bodies
The three Ketone bodies are :
1. Acetone
2. Acetoacetate
3. β - Hydroxy Butyrate

4. Ketone bodies
 Ketone bodies are formed in the mitochondria of the liver cell from acetyl CoA.
Acetyl CoA results from the breakdown of carbohydrates, lipids and aminoacids.
Fate of Acetyl CoA
Normally Acetyl CoA enters the TCA Cycle to generate energy in the form of ATP.
Some of it can leave mitochondria in the form of citrate to participate in the synthesis of
fatty acids.
A third possible fate is the production of ketone bodies, this happens when the acetyl CoA
levels are high and citric acid cycle cannot keep up. This production of ketone bodies is
Ketogenesis.

5. Ketogenesis - Steps
Two molecules of acetyl CoA condense in the presence of Thiolase to form
Acetoacetyl CoA.
 Acetoacetyl CoA condenses with acetyl CoA in the presence of HMG CoA
synthase to form HMG CoA.
 HMG CoA is then converted to Acetoacetate.
 Acetoacetate is reduced to form β - Hydroxy Butyrate
 Acetoacetate is decarboxylated to form Acetone.

7.  Ketone bodies are transported from liver through blood to other
tissues, where acetoacetate and β hydroxy butyrate can be
reconverted to acetyl CoA to produce energy. The heart derives
energy in this way.
 Most tissues obtain energy from glucose. This is important for brain.
If glucose levels are low, during starvation, brain uses ketone bodies
as energy source.
 Ketone bodies can poison and even kill the body cells. When the
body doesnot have the help of insulin, the ketone bodies build up in
blood and then spill over into the urine so that the body can get rid of
them.

8. The levels of acetone are much lower than other two types. It
cannot be converted back to acetyl CoA and is excreted in urine and
breathed out.
 Aceto acetate and β - Hydroxy Butyrate are acidic and if the levels
of ketone bodies are too high, the pH of the blood falls resulting in
Ketoacidosis. This happens in untreated Type I Diabetes and also in
alcoholics after drinking and subsequent starvation.