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Fatty Acid Metabolism, image - Coggle Diagram

- - - - FA synthesis and degradation reciprocally regulated
- - - - Degradation: FA's are broken down in a step-by-step fashion into acetyl CoA, which is then processed in the TCA Cycle
      - Activation of FA -> FA's are linked to CoA before oxidation in mitochondria
        
        FA's are activated on the outer mitochondrial membrane
        
        ATP drives the formation of the thioester linkage between the carboxyl group of FA and the sulfhydryl group of CoA
        
        Activation reaction is catalysed by Acyl CoA Synthetase enzymes
        
        at least 3 synthetase enzymes with different chain length specificities
    - - Hormone sensitive TAG lipase activated -> Glucagon, Adrenaline, noradrenaline, ACTH
        
        Insulin inhibits lipoysis
        
        Free FA -> blood
        
        Bind to serum albumin
        
        ~50% serum protein
        
        acts as carrier to energy requiring tissues
        
        FA->into cells by plasma membrane FA transporters
- - - - Conjugated to carnitine -> carnitine palmitoyl transferase I
        
        Acyl carnitine removed (reverse reaction) -> carnitine palmitoyltransferase II
        
        Carnitine returned by translocase
- - - - Oxidation occurs on beta carbon -> beta oxidation
        
        The oxidation pathway degrades saturated FA's with even number of carbon atoms
- - - - FA synthesis occurs in the cytoplasm
        
        Step 1. -> ATP dependent carboxylation of acetyl-CoA to malonyl-CoA by acetyl-CoA carboxylase (ACC)
        
        Step 2. -> decarboxylation of malonyl group in the condensation reaction catalysed by fatty acid synthase (FAS)
        
        Elongation cycle catalysed by FAS
        
        Repetition of sequence of reactions:
        
        formation of acetyl ACP and malonyl ACP = C4-beta-ketoacyl ACP
        
        condensation of acetyl ACP and malonyl ACP
        
        Reduction using NADPH
        
        Dehydration
        
        Reduction (2nd) using NADPH = C4-acyl ACP
        
        This irreversibe reaction is the committed step of FA synthesis
        
        Acetyl CoA carboxylase (ACC):
        
        contains a biotin prosthetic group
        
        single multifunctional enzyme - 3 activities
        
        essential regulation enzyme of FA metabolism
- - - - Acetyl-CoA is transferred from mitochondria -> cytosol reducing potential of NADH is concomitantly converted into that of NADPH by a series of reactions