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Are there any famous biological processes that depend strongly on a chemical concentration reaching a particular value, like some sort of switch?

E.g. if concentration of chemical x reaches concentration y at cell location z (membrane, organelle etc) then a particular biological process will occur?


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There are several, but I guess the most well known is the neuron action potential, where the concentrations of Na+, K+, and Cl- ions determine the membrane potential of the cell. When the potential reaches a certain level, it triggers the action potential. You can read about this in much more detail on wikipedia, .

But to be pedantic about it, almost every cellular process is concentration dependent.

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thanks that helps. I was also thinking along the lines of "everytime a cut off value is reached, this physiological process occurs" something like cell death, or signalling or repair.... – RRs_Ghost Aug 11 '14 at 23:36
"But to be pedantic about it, almost every cellular process is concentration dependent." Do you think that I could find a proper source on that, like a review paper or something - I need to be able to justify this to my supervisor! – RRs_Ghost Aug 12 '14 at 9:33

Technically any catalysed reaction with a high Km and high Vmax. Also happens in case of co-operative binding reactions. See the oxygen haemoglobin binding.

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