Dihydroxyacetone phosphate can be converted into GAP by the enzyme Isomerase. The above image is from the Bio181 site at the University of Arizona. Humans cannot ferment alcohol in their own bodies, we lack the genetic information to do so. These biochemical pathways, with their myriad reactions catalyzed by reaction-specific enzymes all under genetic control, are extremely complex. We will only skim the surface at this time and in this course.
Alcohol fermentation is the formation of alcohol from sugar.
Humans ferment lactic acid in muscles where oxygen becomes depleted, resulting in localized anaerobic conditions. This lactic acid causes the muscle stiffness couch-potatoes feel after beginning exercise programs. The stiffness goes away after a few days since the cessation of strenuous activity allows aerobic conditions to return to the muscle, and the lactic acid can be converted into ATP via the normal aerobic respiration pathways. In eukaryotes, these processes occur in the mitochondria, while in prokaryotes they occur in the cytoplasm. This process is a prelude to the Kreb's Cycle.