So because we have a higher concentration of H plus ions in the intermembrane space these H plus ions will move down their electrochemical gradient from the intermembrane space to the mitochondrial matrix. And this movement down the electrochemical gradient that was established by protein complex one, three and four synthesizes our ATP molecules from ADP molecules. So adenosine diphosphate and our adenosine triphosphates. Now, we see that for our NADH molecules that are formed inside the mitochondrial matrix and this includes the nadhs formed in pyruvate decarboxylation and the citric acid cycle. For every one NADH molecule formed we form three ATP molecules. So when we oxidize one NADH on complex number one we form three ATPs.