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25 Cards in this Set
- Front
- Back
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Stage One (Priming) of FA synthesis
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Acetyl CoA (from Gkycolysis) is changed to Malonyl CoA by Acetyl CoA Carboxylase which ALWAYS uses Biotin as a cofactor
Only needs to occur once |
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Rxn 1 of FA synthesis
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Coavlent attachement of Malonyl group to the phophopantetheine of the enzyme
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Rxn 2 of FA synthesis
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Condensation of the carboxyl carbon of the ACETYL GROUP with the methylene carbon of the MALONYL GROUP; CO2 is released and a 4 carbon keto chain formed
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Rxn 3 of FA synthesis
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Reduction via NADPH to NADP
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Rxn 4 of FA synthesis
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Dehydration which results in the removal of H2O and formation of a double bond
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Rxn 5 of FA synthesis
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Reduction again via NADPH to NADP which now results in a fully formed 4-carbon saturated (single bond) chain
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Rxn 6 of FA synthesis
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Shift of the completely reduced chain to the cysteine-SH
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Coninuation of FA synthesis
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After rxn 1-6 the process is repeated adding 2C via 3C malonyl CoA to phosphopantetheine until desired chain length (no greater then 16)
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Elongation of LCFA (beyond 16)
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Acyl CoA Synthetase attaches the CoA to palmitate
Occurs in the ENDOPLASMIC RETICULUM Very similar to FA synthesis EXCEPT Fatty Acyl CoA is the substrate which condenses the Malonyl CoA NO phosphopantetheine usually Palmitoyl CoA Results in Stearoyl CoA Abundant in brain |
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Requirements for FA synthesis
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Substrate: Acetyl CoA (cytosol)
Energy: ATP Reducing Power: NADPH from pentose pahway or NADP+ liked malate enzyme Glycerol Backbone |
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Where on the Carbon chain can our body not synthesis double bonds?
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NEVER be synthesized betwen C9 and methyl can add them beyond this
Any FA with double bonds like this are Essential FA (linolenic and linoleic) |
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Desaturation of FA: Creating double bonds
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Occurs in ENDOPLASMIC RETICULUM
Two things oxidized the FA and NADH |
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Linoleic Acid
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Essential FA is Omega-6
Precursor of Arachidonic Acid, which is a source for eicosanoids, prostaglandins and leukotrienes |
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Linolenic Acid
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Essential FA, omega-3
Also forms eicosanoids |
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Conditions for FA synthesis
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LOTS OF REACTANTS
High ATP High Acetyl CoA High NADPH (lots of citrate in TCA Cycle) |
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Short term Regulation of FA synthesis
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via Acetyl CoA Carboxylase
High levels of Citrate Activates it High levels of Palmitoyl CoA DEactivates it via COVALENT Modification Glucagon activates cAMP and PKA PHOSPHORYLATE - inactivate Insulin activates a phosphatase and dephosphorylates - activate |
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Long Term Regulation
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Induction of key enzymes (Acetyl CoA carboxylase, FA synthase, Citrate lyase, malic enzyme, G6PDH)
Enzymes induced when on a good diet over time Enzymes Inhibited when fasting ona a high fat diet |
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How do you prevent futile cycle between FA synthesis and FA breakdown
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Avoided b/c of Malonyl CoA (product of 1st stage of FA synthesis) inhibits CPT1
Inhibits FA from being transferred to carnitine and entering mitochondria |
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First two steps in Triglycerid Synthesis
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Step 1: Glycerol-3-Phosphate synthesis From liver it comes directly from Glycerol From Liver or Adipose is comes from glucose
Step 2: Addition of acyl-CoA cgaubs to form triacylglycerol |
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What are triglycerol made in the liver carried on through the blood?
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VLDL
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Synthesis, processing, and secretion of VLDL
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Apo B100 synthesized in RER
Triacylglycerols synthesized in SER or FA syn. in cytosol Apo B100 and TG are packagedin Golgi to form VLDL VLDL secreted by exocytosis |
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Transport of TG in blood
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Glucose is converted to FA and Glycerol-3-P in liver
TG fromed from FACoA and glycerol-3-P TG incorporated into VLDL VLDL carried to adipose tissue TG in VLDL are hydrolyzed by LPL and the realeased FA taken up by adipose In adipose the FA are resynthesized into TG for storage |
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Insulin's role in FA synthesis
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Stimulates the transport of glucose into adipose
And stimulates the SYNTHESIS and SECRETION of LPL |
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Glucose role FA syntheis?
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Provides the Glycerol-3-phosphate for TG synthesis
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ApoC2 role in FA synthesis
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ACTIVATES LPL (obtained from HDL)
Present in BOTH VLDL and Chylomicrons |
