Alcoholic fermentation. Animation showing the metabolic pathway and reactions involved in fermentation. The starting molecule is the simple sugar glucose (top left). The process of glycolysis converts this into pyruvate (pyruvic acid, centre right). The energy released in this process is used to form the high-energy compounds ATP (adenosine triphosphate) and NADH (reduced nicotinamide adenine dinucleotide). Also shown are phosphate groups (Pi). In the presence of micro-organisms such as yeast (top right), the pyruvate is converted to acetaldehyde (lower right) with the formation of carbon dioxide (CO2). The yeast also promotes the conversion of NADH back to NAD-plus, a process called ethanol fermentation. The end product is ethanol (lower left), the basis of alcoholic drinks. For this animation with labels, see K004/2731.