Ketones

Question 1

Give an example of a ketone body.

Answer 1

Acetone, acetoacetate & b-hydroxybutyrate

Question 2

Where and how are ketones synthesised?

Answer 2

Made in the mitochondrial matrix from beta oxidation of acetyl CoA

Question 3

Where does most of the fatty acid oxidation to ketones take place?

Answer 3

Hepatocytes

Question 4

Which ketones can be oxidised as fuels?

Answer 4

b-hydroxybutyrate is oxidised to acetoacetate. This is then activated to acetoacetyl CoA which can be cleaved into two molecules of acetyl CoA by the thiolase enzyme. The acetyl CoA is then used in the Kreb’s cycle to produce ATP.

Question 5

Why can’t the liver utilise ketone bodies as fuel?

Answer 5

The liver does not have the enzyme thiolase.

Question 6

Why is it important that the liver can’t utilise ketone bodies?

Answer 6

Ensures that other tissues have access to ketone bodies as a fuel source during prolonged starvation.

Question 7

Why does the heart and skeletal muscle consume ketone bodies primarily during starvation?

Answer 7

To preserve glucose for the brain. After glucose stores are used for the brain, it can then use ketone bodies.

Question 8

Is ketone body production slow or fast?

Answer 8

Slow

Question 9

How does diabetic ketoacidosis occur?

Answer 9

Results from a reduced supply of glucose to cells. Causes increase in fatty acid oxidation due to increased glucagon levels. Increased acetyl CoA leads to increased ketone body production

Question 10

What effect do ketone bodies have on the PH of blood?

Answer 10

They lower the PH as ketones are acidic.

Question 11

What is the consequence of low blood PH?

Answer 11

Impairs ability of haemoglobin to bind to oxygen.