<Tr> <Td> ΔG = − 2880 kJ per mol of C H O </Td> </Tr> <P> The negative ΔG indicates that the reaction can occur spontaneously . </P> <P> The potential of NADH and FADH is converted to more ATP through an electron transport chain with oxygen as the "terminal electron acceptor". Most of the ATP produced by aerobic cellular respiration is made by oxidative phosphorylation . This works by the energy released in the consumption of pyruvate being used to create a chemiosmotic potential by pumping protons across a membrane . This potential is then used to drive ATP synthase and produce ATP from ADP and a phosphate group . Biology textbooks often state that 38 ATP molecules can be made per oxidised glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 34 from the electron transport system). However, this maximum yield is never quite reached because of losses due to leaky membranes as well as the cost of moving pyruvate and ADP into the mitochondrial matrix, and current estimates range around 29 to 30 ATP per glucose . </P> <P> Aerobic metabolism is up to 15 times more efficient than anaerobic metabolism (which yields 2 molecules ATP per 1 molecule glucose). However some anaerobic organisms, such as methanogens are able to continue with anaerobic respiration, yielding more ATP by using other inorganic molecules (not oxygen) as final electron acceptors in the electron transport chain . They share the initial pathway of glycolysis but aerobic metabolism continues with the Krebs cycle and oxidative phosphorylation . The post-glycolytic reactions take place in the mitochondria in eukaryotic cells, and in the cytoplasm in prokaryotic cells . </P>

The first electron acceptor in cellular respiration is