Comparing respiration with active transport. Active transport needs energy (ATP) to occur. The regeneration of ATP from ADP (Adenosine Diphosphate) and Pi (Inorganic Phosphate) is called Phosphorylation. The cytochrome system or oxidative phosphorylation is generates 36 ATP per original glucose molecule. Glycolysis generates 4 ATP but the net gain is only 2 ATP because it needed 2 ATP to begin with. Alternative respiratory substrates are fats and proteins.