Fatty acid Beta oxidation Flashcards
What is β-oxidation, and where does it occur?
β-oxidation is the process of breaking down fatty acids into acetyl-CoA. It occurs in the mitochondria of eukaryotes.
How are triglycerides mobilized for β-oxidation?
Triglycerides are hydrolyzed by lipases into free fatty acids and glycerol.
What is the role of carnitine in fatty acid oxidation?
Carnitine transports long-chain fatty acids into mitochondria via the carnitine shuttle (carnitine acyltransferase I and II).
What activates fatty acids for oxidation?
Fatty acyl-CoA synthetase converts fatty acids to fatty acyl-CoA using ATP.
What is the initial step in mobilizing fats for oxidation?
Triglycerides are broken down into glycerol and free fatty acids, which are then transported into tissue cells.
where does it occur?
It primarily occurs in tissues like the heart, skeletal muscles, and liver.
How are free fatty acids activated before entering the mitochondria?
Free fatty acids are converted into fatty acyl-CoA by the enzyme fatty acyl-CoA synthetase. This process requires ATP.
Explain the process of transporting fatty acyl-CoA into the mitochondria for beta-oxidation.
Fatty acyl-CoA is converted to fatty acyl-carnitine by carnitine acyltransferase I (CPT-I) to cross the outer mitochondrial membrane.
Fatty acyl-carnitine is then transported into the mitochondrial matrix, where carnitine acyltransferase II (CPT-II) converts it back to fatty acyl-CoA.
What is beta-oxidation, and what are its main products?
Beta-oxidation is a four-step cyclical process that breaks down fatty acyl-CoA into acetyl-CoA. Its main products are acetyl-CoA, NADH, and FADH2.
Describe the four steps of beta-oxidation and the enzymes involved in each step
Dehydrogenation: Acyl-CoA dehydrogenase forms a double bond and produces FADH2.
Hydration: Enoyl-CoA hydratase adds water across the double bond.
Oxidation: β-hydroxyacyl-CoA dehydrogenase converts the hydroxyl group to a ketone and produces NADH.
Cleavage: Thiolase cleaves the bond, releasing acetyl-CoA and a shortened fatty acyl-CoA.
What happens to the acetyl-CoA produced during beta-oxidation?
Acetyl-CoA enters the Krebs cycle to generate more NADH, FADH2, and a small amount of ATP.
What is the role of NADH and FADH2 produced during beta-oxidation and the Krebs cycle?
NADH and FADH2 are used in the electron transport chain to produce a large amount of ATP through oxidative phosphorylation.
When is beta-oxidation particularly important for energy production?
Beta-oxidation is crucial for energy production when blood glucose levels are low, providing an alternative fuel source by breaking down fats.
How is palmitic acid (a 16-carbon fatty acid) activated for beta-oxidation, and which enzyme is involved?
Palmitic acid is converted into palmitoyl-CoA by the enzyme fatty acyl-CoA synthetase, a process that requires ATP.
Explain the role of carnitine and the enzymes involved in transporting activated fatty acids into the mitochondrial matrix.
Carnitine acyltransferase I (CAT I) adds carnitine to fatty acyl-CoA to form fatty acyl-carnitine, which crosses the outer mitochondrial membrane.
Inside the matrix, carnitine acyltransferase II (CAT II) converts fatty acyl-carnitine back to fatty acyl-CoA, and carnitine is returned to the cytoplasm.
What are the direct products of each round of beta-oxidation?
Each round of beta-oxidation produces one molecule of FADH2, one molecule of NADH, and one molecule of acetyl-CoA, along with a fatty acyl-CoA shortened by two carbons.
How does the oxidation of odd-chain fatty acids differ from even-chain fatty acids?
Odd-chain fatty acids produce propionyl-CoA (a three-carbon molecule) in the final round of beta-oxidation, in addition to acetyl-CoA.
How is propionyl-CoA from odd-chain fatty acid oxidation processed?
Propionyl-CoA is converted to methylmalonyl-CoA by propionyl-CoA carboxylase (requiring biotin and ATP), and then to succinyl-CoA by methylmalonyl-CoA mutase (requiring vitamin B12).
What can succinyl-CoA, produced from odd-chain fatty acid oxidation, be used for?
Succinyl-CoA is a Krebs cycle intermediate and can be used to produce ATP, for gluconeogenesis (glucose synthesis), or for the synthesis of heme and porphyrins.
How does insulin vs. glucagon regulate fatty acid oxidation?
Insulin: Inhibits oxidation (promotes storage via malonyl-CoA).
Glucagon/Adrenaline: Promote oxidation (activate lipases, inhibit ACC).
What inhibits carnitine acyltransferase I?
Malonyl-CoA (from fatty acid synthesis) blocks fatty acid entry into mitochondria.
How does AMPK regulate β-oxidation?
AMPK phosphorylates and inhibits acetyl-CoA carboxylase (ACC), reducing malonyl-CoA → relieves inhibition of carnitine shuttle.
What are ketone bodies, and when are they produced?
Acetoacetate, β-hydroxybutyrate, acetone. Produced in the liver during fasting/starvation as an alternative fuel for the brain and muscles.
