molecules that bind to the enzyme that they inhibit.
competitive inhibitors
have a similar shape to that of substrate molecules. They compete with the substrate molecules to bind to the active site, but no reaction takes place. Instead they block the active site, so no substrate molecules can fit in it
How much the enzyme is inhibited depends on the relative concentrations of the inhibitor and substrate.
If there's a high concentration of the inhibitor, it'll take up nearly all the active sites and hardly any of the substrate will get to the enzyme.
But if there's a higher concentration of substrate, then the substrate's chances of getting to an active site before the inhibitor increase.
So increasing the concentration of substrate will increase the rate of reaction
