correction of answer!

[rtvj]

there was a q posted by someone on action of uncouplers and P/O ratio...I had written that the P/O ratio increases but the right answer is P/O ratio decreases.

Reason: Uncouplers dissipate some of the proton gradient needed for ATP synthesis therefore, more protons have to be transferred across the membrane for each ATP synthesized.This requires more NADPH per ATP synthesized,so P/0 ratio decreases.

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[mam6701e]

It is possible to calculate a P:O ratio (the relationship between ATP synthesis and oxygen consumption) by measuring the decrease in oxygen concentration during the rapid burst of state 3 respiration after adding a known amount of ADP. It is necessary to subtract the basal respiration due to imperfect coupling and the recycling of ATP


P/O ratios used to determine "coupling sites" of ATP

P/O ratio refers to number of molecules of ATP synthesized/pair of electrons
ATP synthesis is measured by uptake of radiolabeled Pi
electron pairs measured by oxygen uptake using an oxygen electrode



P/O ratio

A measure of oxidative phosphorylation; the ratio of phosphate radicals esterified (forming adenosine 5'-triphosphate from adenosine 5'-diphosphate) to atoms of oxygen consumed by mitochondria; normally, the ratio is 3 (starting from nADH).

Synonym: p/O quotient.