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Fatty acid Synthesis - Coggle Diagram

- - - - Inside the mitochondria:
        
        AcetylCoA generated from pyruvate by the action of pyruvate dehydrogenase and by β-oxidation of fatty acids is in the mitochondria.
        
        AcetylCoA reacts with oxaloacetate to form citrate.
      - Citrate transport:
        
        A tricarboxylate translocase (citrate transporter )transports citrate from mitochondria to cytosol.
      - In the cytosol:
        
        Citrate is cleaved by ATP-citrate lyase → acetyl-CoA + oxaloacetate.
        
        This reaction requires the hydrolysis of one molecule of ATP.
        
        Acetyl-CoA is then used for fatty acid synthesis.
        
        Oxaloacetate is converted back to pyruvate for re-entry into
        mitochondria
        
        regeneration of pyruvate
        
        Step 1. Oxaloacetate + NADH + H+ --> malate + NAD+.
        
        Reverse of the TA cycle reaction.
        
        Catalyzed by cytosolic malate dehydrogenase.
        
        Step 2. Malate + NADP+ --> pyruvate + CO2 + NADPH.
        
        Catalyzed by malic enzyme
        
        Pyruvate translocase transports pyruvate into mitochondria
        
        Pyruvate is converted to oxaloacetate
        
        Pyruvate + ATP + CO2 + H2O Æ oxaloacetate + ADP + Pi (reaction of gluconeogenesis)
      - Net Reaction: NADP+ + NADH + H+ + ATP + H2O --> NADPH + NAD+ + ADP + Pi
        
        Thus, transport of acetylCoA to cytosol requires expense of one ATP and conversion of one NADH to NADPH.
- - - - Fx
        
        ACC catalyzes the carboxylation of acetyl-CoA to produce malonyl-CoA
        
        Acetyl-CoA + CO₂ + ATP → Malonyl-CoA + ADP + Pi (catalyzed by ACC)
        
        Malonyl-CoA is the 2-carbon donor used by fatty acid synthase to build long-chain fatty acids like palmitate.
        
        Phosphorylation of acetyl-CoA carboxylase
        --> a decreased level of malonyl-CoA and
        --> increased activity of carnitine palmitoyl- CoA transferase I.
        
        activated ACC - promotes the conversion of
        malonyl-CoA to palmitate in the fatty acid synthesis pathway.
        
        provides the carbons for the synthesis of palmitate on the fatty acid synthase complex
        
        It adds a carboxyl group to acetyl-CoA in a reaction that requires biotin and adenosine triphosphate (ATP)
      - what is it?
        
        an allosteric enzyme which catalyses the primary regulating step in the synthesis of fatty acids
        
        ACC controls whether acetyl-CoA is used for energy (TCA cycle) or stored as fat.
        
        It is activated in the fed state and inhibited during fasting or energy stress.
        
        Acetyl-CoA carboxylase is the rate-limiting enzyme of fatty acid synthesis
- - - - What is it?
        
        Mitochondrial β-oxidation is the pathway by which fatty acids are fully oxidized to carbon dioxide and water.
        
        Fatty acids are transported into mitochondria via the carnitine shuttle (CPT I & II) and broken down by β-oxidation into acetyl-CoA, which enters the TCA cycle to produce ATP.
        
        CPTI
        (key enzyme inhibited)
        
        Located on the outer mitochondrial membrane
        
        It controls the entry of long-chain fatty acids into mitochondria for β-oxidation
    - - what is it?
        
        a metabolic process where fatty acids are built from smaller molecules like acetyl-CoA and NADPH.
        
        Acetyl-CoA (from glycolysis) is converted to malonyl-CoA by ACC, then used by fatty acid synthase to build long-chain fatty acids.
        
        Malonyl-CoA (key inhibitor)
        
        Produced by acetyl-CoA carboxylase (ACC) during fatty acid synthesis
        
        Malonyl-CoA inhibits CPT I, blocking fatty acid transport into mitochondria
    - - Malonyl-CoA acts as an inhibitor:
        
        Malonyl-CoA inhibits CPT I (Carnitine Palmitoyltransferase I).
        
        CPT I is the enzyme that allows fatty acids to enter mitochondria for β-oxidation (fat burning).
        
        This inhibition blocks fatty acid oxidation.
        
        Fatty acids stay in the cytosol, where they are used to synthesize triglycerides.
        
        These triglycerides are stored in adipose tissue → fat deposition.
      - ↑ Insulin stimulates acetyl-CoA carboxylase (ACC).
        
        ACC converts acetyl-CoA → malonyl-CoA, the building block for fatty acid synthesis.