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So why "Quickly"?

Enzymes are very active: this is an example. It's possible to measure the amount of ADP-glucose pyrophosphorylase, one of the enzymes of starch synthesis, in a pea amyloplast (sub-cellular compartment responsible for synthesis of starch). The answer comes out in moles.min-1.ml-1 extract.

Next, it's possible to measure the amount of ATP in the amyloplast preparation. This comes out in moles.ml-1

Dividing the one by the other to calculate the amount of ATP per unit enzyme gives an answer in minutes. This is not an accident - it's the number of minutes the enzyme would take, going flat out, to consume all the ATP (that being one of the substrates of ADPglucose pyrophosphorylase).

The answer is about 3 seconds.