Enzyme

That's a rather large subject!1) PH - needs the right PH to work optimumly, outside of this can become denatured 2) Temperature - too low and the enzymes and substrates don't have kinetic energy so reaction goes down as they're not meeting. Too high and it denatures the enzyme.3) Enzyme/substrate concentration - too little of either means a slower reaction. If you have a lot of say Enzymes and less substrates then the reaction will be a lot faster, however if you have lots of substrate and less enzymes then there will get to a point where the enzymes are working as fast as they can and the optimum reaction rate has been reached.4) Competitive - slows down the reaction rate by blocking the active site5) non-competitive - slows down the reaction rate by changing the shape of the active site (by binding to the allosteric sites)6) reversable inhibitors let go of the enzyme, non-reversable permenantly bind.Hope that helps.

For an enzyme substrate reaction to occur the enzyme and substrate need to collide with sufficient energy and the correct orientation. Each of the above factors will change the rate of reaction; lets look at them one at a time.pH: Enzymes are amino acid chains and it is the bonds between these amino acids that give each enzyme its specific shape. A change in pH will change these bonds and thus change the shape of the enzyme and the shape of its active site. If the active site of the enzyme is denatured it doesn't fit the substrate as well and therefore the rate of reaction decreases.Temperature: Increases in temperature can both increase and decrease rate of reaction. Increased temperature gives both the enzyme and substrate more kinetic energy. In simple terms more speed means more collisions and therefore more reactions. However increasing the temperature too much will cause the enzyme to denature and thus lead to decreased rate of reaction.Increased substrate/enzyme concentration: Increased concentration of enzyme or substrate will lead to more collisions and thus a greater rate of reaction.Inhibitors: Competitive inhibitors have a very similar shape to the substrate and therefore fit into the active site. When in the active site they block the substrate from entering however are not broken down by the enzyme and therefore decrease rate of reaction.Non-competitive inhibitors do not "compete" with the substrate for the active site. They bind at a separate location and work by denaturing the active site such that it is not complementary to the substrate. Irreversible inhibitors form strong bonds with the enzyme and therefore permanently block it from further reactions. Reversible inhibitors do not bind permanently and therefore may only block an enzyme briefly.

Competitive Enzyme Inhibitors work by preventing the formation of Enzyme-Substrate Complexes because they have a similar shape to the substrate molecule.This means that they fit into the Active Site, but remain unreacted since they have a different structure to the substrate. Therefore less substrate molecules can bind to the enzymes so the reaction rate is decreased.Non-competitive Enzyme Inhibitors work not by preventing the formation of Enzyme-Substrate Complexes, but by preventing the formation of Enzyme-Product Complexes. So they prevent the substrate from reacting to form product.Usually, Non-competitive Inhibitors bind to a site other than the Active Site, called an Allosteric Site. Doing so distorts the 3D Tertiary structure of the enzyme, such that it can no longer catalyse a reaction.Since they do not compete with substrate molecules, Non-competitive Inhibitors are not affected by substrate concentration.