Lecture 5 Fatty acid synthesis

Lecture 5 Fatty acid synthesis - BergTymoczkoStryer...

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Biochemistry Chapter 22: Fatty Acid Metabolism PART II Copyright © by W. H. Freeman and Company   Berg • Tymoczko • Stryer
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OAA Summary: Fatty acids from triacylglycerols are a major fuel during fasting and exercise In combination with the citric acid cycle, fatty acids are completely oxidized to CO 2 and H 2 0 Complete oxidation of fatty acids requires the citric acid cycle to function efficiently
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Fatty acid oxidation Ketone Bodies If fatty acid oxidation exceeds the capacity of the citric acid cycle, then acetyl CoA is diverted to form ketone bodies in the liver. Acetyl CoA Conditions leading to ketone body formation include prolonged fasting , high fat/low carbohydrate diets , diabetes: carbohydrates are unavailable and acetyl CoA levels are high. glycolysis
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Sum: 2 acetyl CoA + H 2 0 acetoacetate + 2CoA + H+ Acetyl CoA Ketone bodies Ketone bodies are formed via HMG-CoA thiolase
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The Boon and Bane of Ketone bodies: Ketone bodies are sources of energ
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Utilization of ketone bodies as a fuel The liver is a producer of acetoacetate but not a consumer. WHY? Hydroxybutyrate NADH
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- Insulin: The Boon and Bane of ketone bodies: Deadly metabolites Ketones produced in excess by liver of energy usage by other tissues can lead to ketosis, acidosis, coma and eventually death Diabetic ketosis can occur in patients with insulin-dependent diabetes mellitus: Increased glucagon/insulin ratio Liver is stuck in a gluconeogenic state Chapter 27.4 Pages 802-803
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The Boon and Bane of ketone bodies: the ketogenic diet as a treatment for epilepsy Ketogenic diet: high fat: low carb diet [3:1 or 4:1] Earliest report (fifth century): Hippocrates described a man whose seizures were abolished by starvation (no food/drink) Benefits: 51% of the children on the ketogenic diet >50% reduction in seizures; 32% >90% reduction in seizures Mechanism? acetone hypothesis: acetone = anti-convulsant GABA shunt hypothesis: diet decreases seizure by enhancing GABAergic inhibition (GABA = inhibitory neurotransmitter) (diet + acetyl CoA + α -KG +glutamate/GABA)
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Acyl CoA n-2 + Acetyl CoA Acyl CoA
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Synthesis takes place in the cytoplasm Degradation takes place in the mitochondria Intermediates in synthesis are covalently attached to acyl carrier protein
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Lecture 5 Fatty acid synthesis - BergTymoczkoStryer...

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