A catalyst is a substance which increases the speed of a reaction without being changed or used up in the reaction.
You can make a reaction happen quicker by rising the tempreture.
There is however a limit on how high you can raise the tempreture before the enzyme starts to Denature
All enzymes are proteins and are all made up as aminio acids.
Every enzme has a different shape that fits only one substrate into it.
The substrate must fit into the active site for a chemical action to take place, when the reaction has taken place the sustrate splits into two.
Changing the tempreture can change the rate of the catalyst BUT
If it gets too hot bonds holding the enzyme together break, destroying the enzymes shape.
This is called denaturing
Enzymes in the human body work best at 37 C
The ph can also affect enzyme bonds, they normally work best at the neutral ph of 7, anything above or below it will start to denature.
But this isn't always!
An emzyme in the stomach to break down proteins works best at ph2, meaning its well suited for acidic condidtions.
All enzymes have an optimum point temperature and ph, this is where the enzyme works best at, anything above this the enzyme will start to denature.
Enzymes in digestion
Starch, proteins and fats are BIG molecules.
Sugars, amino acids, glycerol and fatty acids are smaller molecules.
This converts starch into sugars (maltose).
These are in the salivary glands, the pancreas and the small intestine.