Final answer:
Two ATPs are consumed and four ATPs are produced during glycolysis, resulting in a net gain of two ATPs per glucose molecule.
Step-by-step explanation:
During glycolysis, the number of ATP consumed (per glucose molecule) is two, while the number produced is four. However, the net number of ATP produced is two, because the two ATPs used during the initial steps of glycolysis are subtracted from the four ATPs generated in the later steps. It's important to note that in the presence of oxygen, the net ATP produced from glycolysis is often considered zero since the two ATP molecules are used to transport NADH into the mitochondria.
Glycolysis, in essence, is the process by which one glucose molecule is broken down into two pyruvate molecules, yielding two ATP and two NADH molecules. Post glycolysis, during aerobic respiration, each molecule of glucose leads to the production of two pyruvate molecules, and thus the products are multiplied by two for further calculations in the cellular respiration process.