The synthesis of ATP from ADP and Pi by mitochondria
ADP and Pi binding, (2) ATP synthesis, ..
. The medium was that described under Experimental Procedures. The experiment was initiated by adding 400 nmols of ADP and 6.3 nmols of ATP (as contaminant of ADP) to an free from RLM and succinate. After 1.5 min of incubation, 1.0 mg of RLM protein was added to initiate the hydrolysis of the 6.3 nmols of ATP that proceed without the uptake O2 until a seemingly endless state of equilibrium was attained. This period of equilibrium was only interrupted when either succinate (10 Mm) was added to initiate the simultaneous processes of O2 uptake and ATP synthesis or the concentration of O2 was near zero.
that synthesizes ATP from ADP and Pi
In the next steps of glycolysis, the phosphate on the 3-position of the 3-phosphoglycerate is transferred to the hydroxyl residue at position 2. Removal of the elements of water from 2-phosphoglycerate results in the formation of an enolic phosphate compound, phospho(enol)pyruvate (PEP). The free energy of hydrolysis of PEP to form the enol form of pyruvate and Pi is on the order of —4 kcal/mol. In aqueous solution, however, the enol form of pyruvate is very unstable. Thus, the hydrolysis of PEP to form pyruvate is a very exergonic reaction. The AG0 for this reaction is —14.7 kcal/mol, which corresponds to an equilibrium constant of 6.4 x 1010. PEP is thus an excellent phosphoryl donor and the formation of pyruvate is coupled to ATP synthesis. Since two molecules of pyruvate are formed per glucose catabolized, two ATP are formed. Thus the net yield of ATP is two per glucose oxidized to pyruvate.