Ketone Bodies/Protein Catabolism

Question 1

Where does ketogenesis occur?

Answer 1

Mitochondria

(of liver cells)

Question 2

What is the process of ketogenesis? Ketolysis?

Answer 2

Ketogenesis: synthesis of ketones from acetyl-CoA

Ketolysis: breakdown of ketones into acetyl-CoA

Question 3

Which kind of conditions lead to the production of ketone bodies?

Answer 3

Prolonged fasting or starvation

Question 4

Why does ketolysis occur in the brain?

Answer 4

The brain CANNOT use fatty acids for energy when blood glucose levels are altered, so instead ketone bodies are used for an alternative source of energy.

Question 5

What is the process called when amino acids released from proteins lose their amino group?

Answer 5

Transamination or deamidation

Question 6

Where in the body does ketolysis occur?

Answer 6

Brain and muscle cells

Question 7

What are the three ketones produced via ketogenesis?

Answer 7

1. acetoacetate
2. 3-hydroxybutyrate
3. acetone (which is NOT metabolized further)

Question 8

Can RBCs use ketone bodies for energy?

Answer 8

NO!

RBCs can only use glucose because they have no membrane-bound organelles or mitochondria!

Question 9

What are the only two energy sources for the brain?

Answer 9

1. glucose (well-fed state)
2. ketone bodies (fasting state)

Fatty acids cannot cross the blood-brain barrier because they are too big, so they CANNOT be used for energy in the brain.

Question 10

Why do RBCs require/use glucose as an energy source?

Answer 10

Because RBCs have NO membrane-bound organelles or mitochondria so their only option for energy is anaerobic glycolysis (fermentation).