The first steps in the process attach phosphate groups to the sugars. Next comes a series of steps in which the six-carbon sugar is split into two three-carbon pieces, one of which is then rearranged into the structure of the other. After some further rearrangements, this three-carbon molecule loses its terminal carboxylic carbon atom in the form of carbon dioxide gas. The residual part is the two-carbon compound acetaldehyde, which goes next to alcohol if oxygen is lacking, or into another multi-step series of reactions eventually yielding energy, water, and more carbon dioxide if generous amounts of oxygen are available.
