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Oxidation of Fatty Acids
Mitochondrial oxidation of Fatty Acids
Undergraduate 3

Additional Biochemistry Flashcards




Fatty Acid Oxidation Stages
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  1. Beta oxidation- fatty acids undergo oxidative removal of two carbons starting from the carboxyl end, in the form of acetyl-CoA. 16 carbon palmitate has 7 passes thru B-oxidation and the last 2 carbons (what would be 8th pass) are released as acetyl CoA. formation of each acetyl-CoA releases 4Hydrogens and 2 elec.  by dehydrogenase
  2. The acetyl groups of acetyl-CoA are oxidized to CO2 in the TCA cycle in the mito. matrix. Up until this point, B-oxidation and the TCA cycle have been producing NADH and FADH2
  3. NADH and FADH2 now donate electrons to the mitochondrial respiratory chain and energy released by fatty acid oxidation is conserved as ATP
4 Steps of Beta Oxidation


  1. dehydrogenation of fatty acyl-CoA produces double bond between alpha and beta carbon, yielding a trans enol. catalyzed by acyl CoA dehydrogenase which is a flavoprotein with FAD as prosthetic group. The FADH2 group carries the electrons to an electron carrier in the respiratory chain--analogous to succinate dehydrogenation and 2.5 ATP formed per electron pair
  2. Now water is added to double bond of the enol. This reaction is analogous to the fumarase reaction in TCA cycle
  3. step 2 molecule is dehydrogenated via a dehydrogenase which uses NAD(+) as an electron acceptor. Analogous to malate dehydrogenase reaction in TCA. NADH formed donates its electrons to an electron carrier of the respiratory chain. ATP is formed as the electrons go to O2
  4. Thiolase uses step 3 product, beta-ketoacyl-CoA and combines it with free coenzyme A to split off the original carboxy-terminal 2 carbon fragment of the original fatty acid as acetyl-CoA
  • beta oxidation is used to break -CH2- groups in fatty acids, which are stable
  • first three reactions are used to destabilized these groups by adding 2 carbonyls around the alpha carbon, which makes the beta carbon, a ketone, ready for nucleophilic attack by the -SH of CoA catalyzed by tholase
  • acidity of the alpha hydrogen and the resonance stabilization of the carbanion generated by departure of this hydrogen make the terminal -CH2-CO-S-CoA a good leaving group, facilitating alpha-B cleavage
Beta Oxidation Steps are Repeated to Yield Acetyl CoA and ATP
  • In one pass of the beta oxidation sequence, Acetyl-CoA yields 2 pairs of electrons and four protons are removed from the long chain fatty acyl-CoA
  • Palmitoyl-CoA + 7CoA + 7FAD + 7NAD(+)+ 7H2O-->8acetyl-CoA + 7FADH2 + 7NADH + 7H(+)
  • each molecule of FADH2 donates a pair of electrons to respiratory chain, and in turn 1.5 ATP are generated
  • each NADH donates a pair of electrons and 2.5 ATP are generated
  • so for each 2 carbons removed via beta oxidation, 4 ATP are made
  • overall reaction: Palitoyl-CoA + 7CoA + 7O2 + 28Pi +28ADP-->8 acetyl-CoA + 7 H2O + 28 ATP
Acetyl-CoA can be Frhter Oxidized in the Citric Acid Cycle
  • The acetyl-CoA produced through B-oxidation is further oxidized to CO2 and H2O by the citric acid cycle
  • second stage in the oxidation of palmitoyl-CoA and phosphorylations of the third stage: 8acetyl-CoA + 16O2 +80Pi + 80 ADP-->8CoA + 80ATP +16 CO2 + 16H2O
  • complete oxidation of palmitoyl CoA to CO2 and H2O: Palmitoyl-CoA + 23O2 + 108Pi +108ADP--> CoA + 108ATP+ 16CO2 + 23H2O
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