Ketone body metabolism — Flashcards

Flashcard 1: What are the two major ketone bodies produced in a type 1 diabetic patient?

Answer: Acetoacetate and beta-hydroxybutyrate

Extra: The three ketone bodies are acetoacetate, beta-hydroxybutyrate, and acetone. Acetone is produced by the spontaneous decarboxylation of acetoacetate and is considered a minor ketone body (responsible for the fruity breath in DKA).

Flashcard 2: Which enzyme of the fatty acid synthesis pathway utilizes NADPH? _____

Answer: Fatty acid synthase

Flashcard 3: Insulin inhibits _____ formation in the liver because decreased fatty acid degradation provides less acetyl CoA substrate.

Answer: Ketone bodies (Ketoacids)

Flashcard 4: lipoamide

Answer: acyl groups

Flashcard 5: Where does fatty acid oxidation take place?

Answer: mitochondria

Flashcard 6: Where does fatty acid synthesis take place?

Answer: cytoplasm

Flashcard 7: Where does steroid synthesis take place?

Answer: SER

Flashcard 8: Where does cholesterol synthesis take place?

Answer: Cytosol and Smooth Endoplasmic Reticulum (SER)

Flashcard 9: Which intermediate of fatty acid synthesis inhibits beta-oxidation (fatty acid breakdown)?

Answer: Malonyl-CoA inhibits Carnitine Acyltransferase I (CAT-I).

Extra: This is the mechanism that prevents the simultaneous synthesis and degradation of fatty acids. Malonyl-CoA is the product of the rate-limiting step of fatty acid synthesis (catalyzed by Acetyl-CoA carboxylase) and it inhibits the rate-limiting step of beta-oxidation (the carnitine shuttle).

Flashcard 10: What is the rate-limiting enzyme for ketogenesis?

Answer: HMG-CoA synthase (Mitochondrial)

Extra: HMG-CoA synthase is the rate-limiting enzyme of ketogenesis (occurs in mitochondrial matrix). Note: HMG-CoA reductase is the rate-limiting enzyme for cholesterol synthesis (occurs in cytosol).