Glucose is the source of energy in glycolysis. During this process, one molecule of glucose is used to generate two molecules of ATP, two molecules of pyruvic acid and two high-energy-carrying electron molecules of NADH.
Glycolysis is the first step in a process known as cellular respiration. It can occur with or without oxygen. When it occurs without oxygen, cells make small amounts of ATP in a process known as fermentation. There are 10 steps in the process. In addition to ATP, pyruvic acid and NADH, glycolysis also produces two molecules of water. ATP is both generated and used during the process.