Differential equations model it does not work

I need to make the PDF model of G proteins, try to perform a function introducing the variables and equations, but when trying to run it the graph does not work out like the one in the document (section Example 3.2)

I do not know if I'm wrong about something or I just can not achieve the goal of the model.

The function file is: examenisb

function dydx = examenisb (x,y)

ki = 1;

ku = 1;

global Km1;

global Km2;

V1 = y(2)*ki*x(1)/(Km1+y(2));

V2 = y(1)*ku*x(1)/(Km2+y(1));

dadx = V1-V2;

dbdx = -V1-V2;

dydx = [dadx -dbdx]';

The scrypt file is: perrotrabajo

global Km1;

global Km2;

Km1=.001;

Km2=.001;

[x,y]=ode45(@examenisb,[0,2],[0.1 0.1]);

plot(x,y);

xlabel('tiempo (h)')

ylabel('biomasa')

title('Biomasa')

Answer 1

[Sulaymon Eshkabilov]

Hi,

There are a couple of minor (but essential) flaws, such as x(1) used (presumably) instead of y(1) in V1 and V2. Anyhow, to make this long script short, here is a much shorter script with correections w.r.t x(1) --> y(1).

clearvars; clc;
ki = 1; ku = 1;
Km1=.001; Km2=.001;
dydx = @(x, y)[ y(2)*ki*y(1)/(Km1+y(2))-y(1)*ku*x(1)/(Km2+y(1));(y(2)*ki*y(1)/(Km1+y(2))+y(1)*ku*x(1)/(Km2+y(1)))];
[x,y]=ode45(dydx,[0,2],[0.1 0.1]);
plot(x,y); xlabel('tiempo (h)'); ylabel('biomasa'); title('Biomasa'), grid on

Good luck