Final answer:
The two hydrogen ions in glycolysis originate from the oxidation of glyceraldehyde-3-phosphate, resulting in the reduction of NAD+ to NADH, and the release of protons into the solution.
Step-by-step explanation:
The two hydrogen ions (H+) in glycolysis come from a specific reaction that involves the oxidation of glyceraldehyde-3-phosphate (G-3-P).
During this process, a hydrogen molecule (H2) is removed from G-3-P, and this molecule is then split into a hydride ion (H-) and a proton (H+). The hydride ion (H-) is used to reduce NAD+ to NADH, which then carries electrons to the electron transport chain to generate ATP. The protons (H+) are left behind in the solution as a result of this redox reaction.
Through the glycolytic pathway, two molecules of NAD+ are reduced to NADH per glucose molecule, which consequently releases four H+ ions (two from each G-3-P molecule). This oxidative step in glycolysis is crucial for the cell's energy production, as it allows harvested electrons and hydrogen ions to contribute to the formation of ATP later in cellular respiration.