Oxaloacetate

... oxidized into Acetyl CoA producing 2NADH and 2CO2. This is the starting point for the Krebs Cycle. During the Krebs Cycle Acetyl CoA is bound to Oxaloacetate which is the last and most oxidized molecule to come out of the Krebs Cycle. After this binding a reduced molecule Citrate is formed which ...

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... and be impressed with the number of steps. The rate-limiting step for citrate synthase (the mixed condensation reaction between acetyl-CoA and oxaloacetate to form citrate) is the enolization of the acetyl group which then acts as a nucleophile toward bound oxaloacetate. Water--freely available ...

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So I see - it activates the acetate so the acetate CAN bind to the oxaloacetate. Without it, the acetate would not be activated and would not be able to bind to oxaloacetate, right?????

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Here is what I think: the CoA attaches to the acetate and produces acetyl CoA; it isn't stable and makes it very reactive that it binds with the oxaloacetate in the Krebs cycle. CoA-SH then falls off and is free to bind with another acetate in order to bind them with the oxaloacetate in the Krebs ...

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... In order to produce citric acid, the CO2 produced from pyruvate decarboxylation is re-used again by combining it with another pyruvate to produce oxaloacetate (by the action of pyruvate carboxylase and PEP-carboxykinase enzymes). At this stage, we obtain 2 equivalent of oxaloacetate where both ...

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