Lecture 5: Lipid Metabolism Flashcards
What are the functions of lipids?
- Fuel Stores: energy
- Structural Components: cell membrane
- Signaling Molecules
What is a major source of fatty acid synthesis?
Dietary Carbohydrates
Where does FA synthesis primarily occur?
Liver
Adipose Tissue
What happens in Phase 1 of FA Synthesis?
- Acetyl Co-A + OAA –> Citrate (citrate synthase)
- Citrate transported to cytosol via shuttle
- Citrate –> Acetyl Co-A + OAA (citrate lyase)
- OAA –> malate
- malate goes back to mitochondria or becomes pyruvate
What happens in Phase 2 of FA Synthesis?
Acetyl CoA –> Malonyl CoA (acetyl CoA carboxylase)
- rate limiting step!!
- needs biotin
- uses ATP
What does malonyl CoA inhibit?
FA degradation (inhibits carnitine acyltransferase)
What happens in Phase 3 of FA Synthesis?
Elongation of FA via Fatty Acid Synthase
- Condensation: Malonyl CoA added to carbon fatty acyl group
- uses ATP and CO2 generated - Reduction: One of the ketone groups converted to hydroxl
- uses NADPH - Dehydration: Hydroxyl group becomes double bond
- water generated - Reduction: Double Bond removed
- uses NADPH
What are some allosteric regulators of FA synthesis?
Activate: citrate
Inactivate: Long chain FA
What activates and inactivates FA synthesis
Activate: Dephosphorylates
Insulin
Inactivate: Phosphorylates
Glucagon
Epinephrine
AMP
Where does FA elongation take place? What is used as a carbon donor for elongation?
Smooth ER: Malonyl CoA
Mitochondria: Acetyl CoA
Where are double bonds introduced?
In Smooth ER, double bonds can be introduced: 4-5 5-6 6-7 9-10
What is linoleic acid a precursor of?
omega-6
- prostaglandins
- leukotrienes
- thromboxanes
What is linolenic acid a precursor of?
omega-3
-DHA
What is the major storage of Fatty Acids?
Triglycerides (TAGs)
