Description and explanation of the effects of temperature, competitive and non-competitive inhibitors, pH and substrate concentration.

Temperature
At low temperatures there is a less energy, the substrates will move around more slowly making them less likely to reach the active site.
At optimum temperature there is a lot of energy and as substrates move around more they more frequently end up in the active site.
Past optimum temperature there is too much energy for an enzyme, and the bonds holding it together will break: this is called denaturing.

PH
Different types of enzymes have very different optimum PHs.
Above and below this PH the bonds holding the enzyme together will break, and the amino acids will have their charges changed, preventing them from forming bonds with the substrate.

Substrate concentration
At low concentration, substrates get into the active site less frequently meaning they react little.
At medium concentrations, substrates will get into the active site a lot meaning they are constantly reacting.
At high concentrations there will be a substrate in the active site all the time: after this, adding more substrate will not speed up the reaction, because the enzymes are always busy anyway (this is why at a certain point increasing the substrate concentration makes no difference to the rate of reaction.)

Competitive inhibitors
These compete with substrates to bond with the active site of an enzyme.
Once they have bonded with the active site they block it so substrates can't bond with it.
The bonds are usually weak hydrogen bonds, however, and will soon break (reversible.)
The effects of competitive inhibitors can be reduced by adding more substrate because that means it has more substrates to compete with, so a lower chance of getting into the active site.

Non-competitive inhibitors
These bind to an allosteric site (away from the active site) which distorts the active site to make it less complimentary to its substrate. This is usually an irreversible strong covalent bond