Calculating the P:O ratio

For normal incubations (i.e. when there is no inhibitor or uncoupler added) you should calculate the ratio of ADP phosphorylated : atoms of oxygen consumed; this differs for different substrates, and you should work out why this is so.

If you save results to print out when you finish running the program, you will receive a print out like that shown on the right for each saved experiment.

You should draw straight lines, as shown above, to determine the % oxygen saturation:
A) at the time that the mitochondrial preparation is added
B) at the time that ADP is exhausted

Then measure the distance from 0 - 100% oxygen saturation

In this example, by measurement (on the original printed graph)t:
100% oxygen saturation (1327 nmol O) = 78 mm

point A = 72.5 mm = 72.5 / 78 = 0.929 x 1327 nmol O = 1233 nmol O

point B = 40 mm = 40 / 78 = 0.512 x 1327 nmol O = 680 nmol O

Hence, difference = 1233 - 680 = 552 nmol O

You should be able to calculate the P:O ratio from this value (the amount of oxygen used) and the amount of ADP you added in the experiment.