Oxygen consumption rate (OCR) is defined as the rate at which cells consume oxygen. I reason that for cells not capable of photosynthesis, OCR is strictly non-negative.

That was until I read this article which provides a graph with negative OCR values. Could someone enlighten me as to how this might be possible? If the cells are consuming no oxygen, I would expect OCR to be zero, not negative.

enter image description here

Scientific Paper:


  • $\begingroup$ Start by asking if the zero in the scale actually zero, an arbitrary baseline, or a proxy measurement? in this case it appears to be a proxy so zero might not represent actual zero. $\endgroup$
    – John
    Jan 1, 2018 at 6:42

1 Answer 1


The diagram is not clear. They should write "change of oxygen consumption rate".

The caption of the diagram makes it clearer what they are describing:

" In A, a time course for measurement of oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) is shown under basal conditions, [...] ".

So basically they are measuring oxygen consumption rate under basal conditions and apply some chemicals and depict the change in oxygen consumption rate in a diagram, given in percentage.

  • $\begingroup$ Hi there, thank you for your answer. Will your answer still hold if the OCR was measured in units of pmol/min? (i.e. moles of oxygen per unit time) $\endgroup$ Dec 31, 2017 at 16:45

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