An enzyme is a biological catalyst, and a catalyst is something that causes or speeds up a chemical reaction however, it does not get used up in the reaction. The way in which enzymes work is similar to a lock and key. The enzymes are the locks and the substrates are the keys. The enzyme will only accept the correct substrate, much like a lock will only accept the correct key. The substrates go into a place called the 'active site' on the enzyme, and the enzyme causes (or speeds up) a chemical reaction.
There are two main types of enzymes. Some are 'breakers', so a substrate will go into the active site and two substrates will some out (c → a+b). Others are 'builders', essentially the opposite of breakers. Two substrates will go in and one substrate will come out (a+b → c).
Enzymes are basically protein molecules made up of long chains of amino acids. These long chains are folded in order to create the active site.
All enzymes have five important properties;
They are all proteins
Each enzyme controls one particular reaction
They can be used again and again
They are affected by temperature
They are affected by pH
Looking at the first point 'They are all proteins', when you heat a protein, it changes shape. For example; hair. Hair is a protein, and when you heat hair, it changes shape. This is called denaturing. Therefore, as enzymes are proteins, when heated they change shape or 'denature'. Going back to the 'lock and key' theory, once the 'lock' (or enzyme) has changed shape, it will no longer accept the 'key'.
For a preliminary experiment, we looked at collision theory and how temperature increases reaction rate. Temperature is simply how fast particles are moving. The faster the particles are moving, the more likely they are to collide and therefore, more likely to react.
We put a small amount of a catalyst into the bottom of a reaction tube along with some Hydrogen Peroxide (H2 O2) about ¼ full. Then, using a bung, a delivery tube, a water bath and a collection tube, we counted how many bubbles appeared in the collection tube.
We performed this at two