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Q10 is the increase in a rate (e.g. activity of an enzyme) observed with a 10 degree temperature increase.

According to Wikipedia:

enter image description here

It is apparent that the units of R (e.g. mol/g/s) cancel out, but what about the units of temperature? Does Q10 have units? It seems the units would be "per 10C", but it is not clear how this comes from the referenced equation

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1 Answer 1

up vote 4 down vote accepted

enter image description here

Figure. A schematic diagram showing the effect of the temperature on the stability of an enzyme catalysed reaction. The curves show the percentage activity remaining as the incubation period increases. From the top they represent equal increases in the incubation temperature (50º C, 55º C, 60º C, 65º C and 70º C).

The enter image description here is a unitless number, that summarizes the effect of raising temperature 10º C on the rate of a chemical reaction. A enter image description here of 2.0 suggests that raising the temperature of a system by 10º C will effectively double the rate of the reaction. This value would be expected for most chemical reactions occurring within normal physiological temperatures.

Mathematically, enter image description here can be represented by the following expression:

enter image description here


t2 = higher temperature    k2 = rate at t2
t1 = lower temperature     k1 = rate at t1

Ussualy the temperature difference is about 10º C, then you can simplify the equation

enter image description here

Edit: You can easly calculate k form Arrhenius equation enter image description here

where k is the kinetic rate constant for the reaction, A is the Arrhenius constant, also known as the frequency factor, enter image description here is the standard free energy of activation (kJ M-1) which depends on entropic and enthalpic factors, R is the gas law constant and T is the absolute temperature.

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how do you calculate k, are the curves in the figure something like e^{-kt}? –  Abe Jun 12 '12 at 17:12
Here k is a rate constant like R in your wikipedia example, and for the figure the curves show the percentage activity remaining as the incubation period increases. –  friveroll Jun 12 '12 at 17:44
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