Lipid metabolism — Flashcards

Flashcard 1: lipoamide

Answer: acyl groups

Flashcard 2: Where does fatty acid oxidation take place?

Answer: mitochondria

Flashcard 3: Where does fatty acid synthesis take place?

Answer: cytoplasm

Flashcard 4: Where does steroid synthesis take place?

Answer: SER

Flashcard 5: Where does cholesterol synthesis take place?

Answer: Cytosol and Smooth Endoplasmic Reticulum (SER)

Flashcard 6: 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 7: 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).

Flashcard 8: Rate-limiting enzyme of cholesterol synthesis

Answer: HMG-CoA reductase

Extra: HMG-CoA Reductase converts HMG-CoA to Mevalonate. Statins (e.g., Atorvastatin) are competitive inhibitors of this enzyme.

Flashcard 9: What is the function of Lecithin-cholesterol acyltransferase (LCAT)?

Answer: Esterification of cholesterol (in HDL)

Extra: LCAT is activated by ApoA-I. It converts free cholesterol into cholesterol esters on the surface of HDL, which then move into the core of the HDL particle (part of reverse cholesterol transport).

Flashcard 10: What is the function of Cholesterol Ester Transfer Protein (CETP)?

Answer: Facilitates the exchange of cholesteryl esters (CE) from HDL to VLDL/LDL in exchange for triglycerides (TG).

Extra: CETP mediates the transfer of cholesterol esters from HDL to VLDL, IDL, and LDL, while simultaneously transferring triglycerides from these B-100-containing lipoproteins back to HDL. Inhibition of CETP increases HDL levels.