8 Questions
Which enzyme catalyzes the formation of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) from acetoacetyl-CoA?
3-hydroxy-3-methylglutaryl-CoA synthase
What are the main products formed during the hydrogenation of acetoacetate?
3-hydroxybutyrate and NAD+
Where specifically does ketogenesis occur within the liver cells?
Mitochondria
Which of the following compounds is a starting material for ketogenesis?
Acetoacetyl-CoA
What is the primary ketone body found in blood and urine during ketosis?
3-hydroxybutyrate
Which enzyme is responsible for the split of acetyl-CoA from HMG-CoA?
3-hydroxy-3-methylglutaryl-CoA lyase
From which molecule does acetoacetate spontaneously decarboxylate to form acetone?
Acetoacetate
Which two molecules can condense to form acetoacetyl-CoA?
Two acetyl-CoA
Study Notes
Ketone Bodies
- Ketone bodies are produced by the liver under metabolic conditions with high fatty acid oxidation rates.
- Ketone bodies consist of acetoacetate, 3-hydroxybutyrate (β-hydroxybutyrate), and acetone.
Ketogenesis
- Ketogenesis occurs in the mitochondria of liver cells.
- Enzymes responsible for ketone body formation are 3-hydroxy-3-methylglutaryl-CoA synthase and 3-hydroxy-3-methylglutaryl-CoA lyase.
- Ketogenesis is an alternative way of fatty acid oxidation for energy production in extrahepatic tissues.
Biosynthesis of Ketone Bodies
- Acetoacetyl-CoA is the starting material for ketogenesis and can be formed from two acetyl-CoA molecules or directly from the terminal four carbon atoms of an acyl-CoA during β-oxidation.
- Condensation of acetoacetyl-CoA with acetyl-CoA forms 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) in the presence of water.
- 3-Hydroxy-3-methylglutaryl-CoA lyase enzyme splits acetyl-CoA from HMG-CoA, forming acetoacetate.
- Acetoacetate can be converted to other ketone bodies through hydrogenation to form 3-hydroxybutyrate or spontaneous decarboxylation to form acetone.
- 3-Hydroxybutyrate is quantitatively the predominant ketone body present in the blood and urine in ketosis.
Learn about ketogenesis, acetoacetate, 3-hydroxybutyrate, and acetone production in the liver under conditions of high fatty acid oxidation. Understand their role in energy production for extrahepatic tissues.
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