Beta oxidation Flashcards
why are fats the most concentrated store of metabolic energy
- it is chemically very reduced, releases max amount of free energy when oxidized all the way to CO2
- very hydrophobic and can be stored nearly water free
steps in the complete oxidation of fatty acids to CO2 and H2O
- Beta oxidation: gives rise to acetyl-CoA and reduced cofactors
- the citric acid cycle (oxidizes CO2)
- the electron transport chain (oxidize NADH and FADH2)
who identified beta oxidation
Franz Knoop
discovery about fatty acid catabolism
fatty acids are catabolized 2 carbons at a time
how are fatty acids prepared for catabolism
- activating them to fatty acyl CoA
- Acyl CoA synthetase occurs in the outer mitochondrial membrane
fatty acid activation
- nucleophilic oxygen of the fatty acid attacks the alpha phosphate of ATP forming PPi (immediately hydrolyzed to 2Pi) and acyl adenylate
- the nucleophilic thiolate anion form of CoASH reacts with acyl adenylate. AMP is the leaving group, fatty acyl-CoA thioester is formed
synthetase
- enzyme that combines 2 small molecules to form a larger molecule with the help of ATP energy
synthase
- enzyme that combines 2 small molecules to form a larger molecule
- DOES NOT require ATP
mitochondrial matrix
- where beta-oxidation happens
- outer membrane is freely permeable to small molecules
- inner membrane is highly impermeable to most solutes
acyl-carnitine / carnitine transporter
- transports fatty acids with > 12 carbons into the mitochondria
- found in the form of fatty acyl-carnitine esters
Beta-oxidation pathway
- oxidation
- hydration
- oxidation
- thiolysis
- each pass through the cycle produces an acetyl CoA and shortens the chain by 2 carbons
B-O Step 1: oxidation by FAD
forms a double bond between a and B carbons of fatty acyl coA
- becomes trans-delta2-enoyl-CoA
- creates a double bond
- enzyme: acyl-CoA dehydrogenase
B-O step 2: hydration
- water is added across the double bond to give an alcohol at the beta carbon
- product is L-B-hydroxy-acyl-CoA
- enzyme: enoyl-CoA hydratase
B-O step 3: oxidation by NAD+
- produces B-Ketoacyl-CoA
- enzyme: B-hydroxyacyl-CoA dehydrogenase
B-O step 4: thiolysis
- breaks bond between a and B carbons
- produces acetyl-CoA
- enzyme: thiolase
when is beta-oxidation repeated until
- once all carbon atoms in the chain are released as acetyl CoA
- complete oxidation of palmitic acid produces 8 molecules of acetyl CoA
- 1 FADH2 is formed per turn (7 total)
- 1 NADH is formed per turn (7 total)
what is carnitine used for
to deliver triacylglycerols from the intestine to tissues via the bloodstream
Acyl-CoA synthetase
activates fatty acids for oxidation
- occurs in the mitochondrial membrane
- Combines fatty acid and CoA with help of ATP
what is true of the oxidation of 1 mole of palmitate
- activation of the free fatty acid requires the equivalent of 2 ATP
- inorganic phosphate (PPi) is produced
- 8 mol of acetyl-CoA are formed
