Need help with my code for a graph. Figure provided

Please look at graph 2b.

x is the different value of the ip3 that is changing.

ca=1e-7
d1=1.3e-7
d2=0.000001049
d3=9.434e-7
d5=8.234000000000001e-8
x=linspace(10.^-7.5,10.^-4.5)
y=[((ca.*x).*d2)./[(ca.*x)+(x.*d2)+(d2.*d1)+(ca.*d3)].*(ca+d5)].^3
plot(x,y)

Once the graph is plotted I go into axes properties, and switch the x axis from linear to logarithmic. I get something quite similar, but still incorrect.

Also this is for a project, so if there is a more elegant way to do this it would be awesome to know.

If the above figure does not show here is the link

http://i50.tinypic.com/5cj8le.png