The process of movement of ions across the semi-permeable membrane by diffusion and, this takes place down the electrochemical gradient, is commonly known as Chemiosmosis. An example of semi-permeable membrane can be the membrane inside of mitochondria. Ions are the molecules that have a net electric charge, examples can be Na⁺ and Cl^–, and more specifically for chemiosmosis it generates energy and H⁺_. Through the process of chemiosmosis, in cellular respiration takes place in the production of ATP (Adenosine Tri-phosphate). The process of chemiosmosis, includes pumping of protons that takes place through the exceptional channels that are present in the membranes of mitochondria. The pumping of the protons generates a proton (H⁺) gradient. When the proton gradient is established, the diffusion of protons take place through the transportation protein that is known as ATP synthase. The flow of hydrogen acts as a catalyst that helps in the pairing of phosphate with the ADP (Adenosine Di-phosphate) to form the ATP.

The chemiosmosis process generates 90 percent of the ATP that is being created during the catabolism of aerobic glucose. In mitochondria, the production of ATP by the use of chemiosmosis is known as oxidative phosphorylation. This method is also used in the light reactions of photosynthesis that harness the energy from the sunlight, during the process of photophosphorylation. The reaction results in the production of ATP from the energy of the electrons that is being removed from the hydrogen atoms. These atoms were initially a part of the glucose molecules. The oxygen molecules are reduced by the electrons to oxygen ions. After that water is formed by the extra electrons that attract hydrogen ions from the surrounding.