Question

During high-intensity exercise such as sprinting or lifting a very heavy weight, energy is provided to cells by the phosphogen system (or ATP-PC system), which only works for a few seconds. If the diffusion constant of ATP is 3 ×10⁻¹⁰ m² s^-1, how far could this molecule diffuse in 5 seconds? (not 5.477E-5 m)

Answer 1

The diffusion distance is given by the formula

where

is mean square distance. Thus, will give us how far the molecule diffused in the given time.

is a numerical constant depending on the dimensionality of the diffusion. It is for one dimensional diffusion, for two-dimensional diffusion, and for three-dimensional diffusion.

is the diffusion constant

is the time given.

The purported wrong answer in the question is the answer when dimensionality of the diffusion is taken as one.

Therefore, the diffusion can be either two-dimensional or three-dimensional.

Assuming the diffusion is two-dimensional

Assuming the diffusion is three-dimensional