How Is Water Formed During Cellular Respiration?

By JacobS

The human body is about 60 percent water by weight. Not only is water important for all life on Earth, but it is also a key molecule in the facilitation of certain reactions and processes, including the ones present in cellular respiration.

Cellular Respiration

The formation of water is the final step in the process of cellular respiration. It occurs after glucose has already been broken down within the mitochondrion, which is kind of like the main powerhouse of the cell where most of the metabolic process occurs.

Electrons and Hydrogen Ions

The citric acid cycle, also known as the Krebs cycle, produces several molecules that donate free electrons and hydrogen ions (charged particles of hydrogen) to a process known as the electron transport chain. The purpose of this action is to produce molecules of ATP (adenosine triphosphate), the main energy carrier of the cell.

Electron Transport Chain

In the electron transport chain, the movement of electrons galvanizes the hydrogen ions to move across the mitochondrion membrane. The hydrogen ions must enter several different stages, but eventually the action of the hydrogen ions being channeled back through the membrane is enough to produce the ATP necessary for the sustenance of the cell.


At the very end of the process, electrons and hydrogen ions need something to bind to. Otherwise, hydrogen ions can no longer help synthesize ATP, and the entire process of cellular respiration will grind to a halt. Fortunately, oxygen that was transported from the lungs by hemoglobin in the blood provides a suitable acceptor.


In the very last step of cellular respiration, two free electrons and two hydrogen ions will react with a single oxygen atom, creating one water molecule. Because electrons are negatively charged and the hydrogen ions are positively charged, their charge will cancel each other out.