Fatty Acid Synthesis Flashcards
Where are fatty acids synthesized?
Cytoplasm
What is the first step in FA synthesis?
Moving Acetyl CoA to the cytoplasm for FA synthesis
How is acetyl CoA moved across the mitochondrial membrane to the cytosol?
Acetyl CoA is condensed with Oxaloacetate to form citrate, which is transported across the membrane.
What is the function of ATP-citrate lyase?
Breaks citrate down into acetyl CoA and oxaloacetate in the cytosol
Where is NADPH synthesized for the synthesis of palmitate?
8 molecules are formed when 8 acetyl CoA are transported to the cytoplasm
Remaining 6 come from pentose phosphate pathway
What is the rate limiting step for fatty acid synthesis?
Formation of malonyl CoA
Catalyzed by Acetyl CoA carboxylase
What is the active structure of Acetyl-CoA carboxylase?
Active enzyme exists as filaments, monomers are inactive
How is Acetyl CoA carboxylase regulated by phosphorylation?
Inactivated via phosphorylation by AMP-activated protein kinase
Activated by dephosphorylation by protein phosphatase 2A.
What triggers phosphorylation of acetyl-CoA carboxylase?
Glucagon and Epinephrine
How does citrate influence the activity of acetyl-CoA carboxylase?
Allosterically activates it by facilitating the polymerization of inactive dimers into active filaments
Phosphorylation reduces sensitivity to stimulating effect of citrate
What molecule counteracts the stimulatory effect of citrate?
Palmitoyl CoA
How does insulin affect fatty acid synthesis?
Stimulates synthesis by stimulating dephosphorylation of acetyl-CoA carboxylase
What is adaptive control of Fatty Acid synthesis?
Fasting then feeding will increase acetyl CoA carboxylase activity, increasing fatty acid synthesis
Describe the structure of Fatty Acid Synthase.
Two identical chains folded into 3 domains joined by flexible regions
7 catalytic sites
What is the function of acyl carrier protein?
Carries the intermediates during FA synthesis
