where does the phosphate come from in atp
Adenosine triphosphate In terms of its structure, ATP consists of an adenine attached by the 9-nitrogen atom to the 1′ carbon atom of a sugar (ribose), which in turn is attached at the 5′ carbon atom of the sugar to a triphosphate group. In its many reactions related to metabolism, the adenine and sugar groups remain unchanged, but the triphosphate is converted to di- and monophosphate, giving respectively the derivatives ADP and AMP. The three phosphoryl groups are referred to as the alpha (α), beta (β), and, for the terminal phosphate, gamma (γ).
Mitochondrial intermembrane space The intermembrane space is chemically similar to cytosol, but includes a large amount of small proteins as well. As electrons move down the proteins in the electron transport chain, the electrons lose energy to bring H+ ions from the mitochondrial matrix into the intermembrane space. As a concentration gradient of hydrogen ions forms, a protein called ATP synthase harnesses the potential energy of these ions and starts chemiosmosis, where the H+ ions reenter the matrix via this enzyme bound to the cristae (folds of the inner membrane). ADP and a phosphate group are combined to form ATP.