Incoming acetyl co-enzyme A gets combined with a substance called oxaloacetate . Through a number of steps and intermediary compounds reacting with various enzymes, the acetyl coA is burned into carbon dioxide and water, while releasing 36 molecules of ATP for each incoming fuel molecule. Effect of exercise All these different factors come into play when a person begins sustained exercise. In the initial stages, light exertion has the effect of activating neural pathways. As exercise continues, either glycogen levels decrease or exercise intensity increases.
More glucose is needed, and free glucose in the blood is the next immediate source.
The first compensatory effect is to restore normal plasma glucose levels. Glucagon and ephinepherine activate the breakdown of liver glycogen into glucose and this goes into the blood. At the same time, these hormones are acting on adipocytes and triggering the breakdown of triglycerides into free fatty acids. The ketones diffuse directly into the blood and then are taken up by muscle cells, where they are easily reconverted into acetyl co-enzyme A and burned for energy via the Krebs cycle. If you look at this sequence, you can see that the initial stages of exercise are essentially running on glycolysis.