"Yes, everything could be converted to ketons and then used as fuel in mitochondria. I was just trying to keep it simple!!!!"

It is not just "simple" it is "wrong." You are implying that conversion of carbohydrate, fatty acids and amino acids to energy requires being to converted to ketone bodies as an intermediae. This is 100% false! 6-carbon glucose gets converted to two molecules of 3-carbon pyruvate, each of which then gets converted to 2-carbon acetyl-CoA via the pyruvate dehydrogenase enzyme in the mitochondria. Fatty acids are broken down by beta oxidation in the mitochondria to release multiple 2-carbon acetyl-CoA molecules. Acetyl-CoA derived from either glucose or fatty acids then enters the citric acid cycle to generate NADH and FADH2, which then enter the ETC for oxidative phosphorylation and ATP production. Ketone body production, which occurs almost exclusively in the liver, occurs when the citric acid cycle intermediate becomes too low (i.e. fasting, starvation, low insulin in type 1 diabetes) and there in no longer enough 4-carbon oxaloacetate (OAA) to combine with 2-carbon acetyl-CoA to produce the 6-carbon citrate. The "excess" acetyl-CoA is then diverted to ketogenesis (ketone body production) in the liver, such that other tissues can use this valuable energy source in time of low glucose (fasting, starvation, etc).

BearDownAZ