function [ dXdt ] = presentation_ka_nw(t,X)
% this function defines the differential equation for the enzymatic
% reations
global r1 rmin1 r2 rmin2 r3

dXdt = zeros(size(X));

a = X(1); %alphaketo
b = X(2); %glutamate
c = X(3); %glutamine

dadt = -(r1*a) + rmin1*b - (r3*a*c);
dbdt = r1*a -(rmin1*b) + rmin2*c -r2*b + (2*r3*a*c);
dcdt = -(rmin2*c) + r2*b -(r3*a*c);

dXdt(1) = dadt;
dXdt(2) = dbdt;
dXdt(3) = dcdt;

end