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Questions and Answers
Which of the following compounds is classified as a true ketone?
Which of the following compounds is classified as a true ketone?
- Acetoacetate (correct)
- β-hydroxybutyrate
- Acetone (correct)
- All of the above
Where does the synthesis of ketone bodies primarily occur in the body?
Where does the synthesis of ketone bodies primarily occur in the body?
- Small intestine
- Kidneys
- Liver (correct)
- Pancreas
What type of compound is β-hydroxybutyrate with respect to its ketone classification?
What type of compound is β-hydroxybutyrate with respect to its ketone classification?
- True ketone
- Protonated ketone
- Not a ketone (correct)
- Carboxylic acid
Which of the following statements about ketone bodies is accurate?
Which of the following statements about ketone bodies is accurate?
What is the primary source of Acetyl CoA for ketogenesis?
What is the primary source of Acetyl CoA for ketogenesis?
What is the first step in the synthesis of ketone bodies?
What is the first step in the synthesis of ketone bodies?
Which enzyme catalyzes the conversion of acetoacetyl CoA to HMG CoA?
Which enzyme catalyzes the conversion of acetoacetyl CoA to HMG CoA?
What product is formed when HMG CoA is cleaved?
What product is formed when HMG CoA is cleaved?
Which of the following amino acids are considered ketogenic?
Which of the following amino acids are considered ketogenic?
How are ketone bodies transported from the liver to other tissues?
How are ketone bodies transported from the liver to other tissues?
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Study Notes
Ketone Body Synthesis
- Ketone bodies are formed through the breakdown of fatty acids in a series of enzymatic reactions.
- Acetyl CoA Condensation: Thiolase catalyzes the condensation of two acetyl CoA molecules to produce acetoacetyl CoA.
- HMG CoA Production: HMG CoA synthase combines acetoacetyl CoA with another acetyl CoA, forming β-hydroxy-β-methylglutaryl CoA (HMG CoA), a key regulatory step.
- Cleavage of HMG CoA: HMG CoA lyase cleaves HMG CoA into acetoacetate and another acetyl CoA.
- Decarboxylation of Acetoacetate: Acetoacetate can spontaneously decarboxylate, yielding acetone, a volatile compound.
- Reduction of Acetoacetate: Enzymatic reduction by a dehydrogenase converts acetoacetate to β-hydroxybutyrate (3-hydroxybutyrate), a significant ketone body.
- Ketogenic Amino Acids: Certain amino acids like leucine, lysine, and phenylalanine can be converted into acetoacetate or acyl CoA, contributing to ketone body production.
Utilization of Ketone Bodies
- Ketone bodies are water-soluble, facilitating their transport from the liver to other tissues for energy utilization.
Ketone Bodies Overview
- Three primary ketone bodies are acetone, acetoacetate, and β-hydroxybutyrate; only acetoacetate and β-hydroxybutyrate are true ketones.
- β-hydroxybutyrate lacks a keto group (C=O), distinguishing it from the other two ketone bodies.
- Ketone bodies serve as energy sources, while acetone is non-metabolizable and acts merely as a byproduct.
Ketogenesis Process
- Ketogenesis occurs in the liver, specifically within the mitochondrial matrix.
- Acetyl CoA, generated from fatty acid oxidation, pyruvate, or certain amino acids, is the precursor for ketone body synthesis.
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