Question

Uptake of inorganic nutrients by phytoplankton often is modeled using the Michaelis-Menten equation. The half-saturation constant for uptake of both ammonium and nitrate by the alga Asterionella formosa (a diatom), KS, is ∼1 M. Estimate the concentrations of ammonium and nitrate at which uptake of these N forms is 90 and 95% of the alga’s maximum uptake rate.

Answer 1

The concentration of ammonium is 9 M when the uptake is 90% of the maximum uptake.

The concentration of nitrate is 19 M when the uptake is 95% of the maximum uptake.

In the question its mentioned that the uptake of ammonium is 90% of the maximum uptake and that of nitrate is 95% of the maximum uptake hence we can take the value os V in terms of V_max. K_s value is given as 1 M.