Effect of concentration of copper sulphate on the action of amylase to break down starch Paper
There are two ways that we could have consumed copper sulphate. Water pipes are responsible for transporting water, and some of them are made out of copper. Copper pipes can become rusted if there is high sulphate content in the water, basic copper sulphate is precipitated which can grow through the pipe wall creating pit holes . Copper sulphate is also used in some places to treat sewer lines, tree roots are constantly looking for water and organic sources and sewer lines are the perfect site for them. Tree roots will penetrate and damage the pipes which will is expensive to repair.
Copper sulfate kills tree roots without killing the tree or other plants , therefore copper sulphate is poured into these pipes to kill the tree roots. This way there is a small chance that copper sulphate will leak into the pipes that are used for drinking. Copper sulphate can do a lot of harm to the human body, but very little has been discussed on the effect of copper sulphate on amylase, which is an enzyme that is present in human saliva and in the small intestines, therefore I want to perform an experiment to find out how the concentration of copper sulphate will affect the action of amylase.
Copper sulphate has the formula CuSO4 and is commonly used to control fungus diseases , both in agriculture and medicine. According to the Turkish Journal of Zoology (source 16), copper sulphate can inhibit the activity of amylase by 5%.
Enzymes- Alpha Amylase
Enzymes are biological catalyst, and a catalyst is substance which speeds ups a chemical reaction but remains unchanged itself at the end.  Enzymes are biological catalyst because they are globular protein molecules that are made by living cells to speed up reactions inside a living organism. There are three levels of structure of enzyme; the primary, secondary and tertiary structure. The primary structure is the order and type of amino acids that made up the chains. The secondary structure is the folding of the chains into either beta sheets or helix.
The tertiary structure is the overall folding of the chains into a three dimensional, globular shape with an active site of a specific shape. Amylase is an enzyme made in the salivary gland and pancreas in the human body. They are used to break down carbohydrates, in other words starch are broken down to sugar or glucose . Enzymes are sensitive to its environment, changes to the pH and temperature will affect the structure and function of enzyme, and therefore these factors have to be kept the same during the experiment.
How does an enzyme work?
Being a biological catalyst, enzymes work by providing an alternative pathway that has a lower activation enthalpy for reaction to take place therefore speeding up reactions without changing any other factors such as temperature and concentration. Many reactions in the body will not happen at all because the activation enthalpy is too high to reach, therefore the presence of enzymes are vital in every organisms for reactions to take place and to stay alive.
The first proposed theory of how the enzyme work is called the ‘lock and key’ hypothesis, where the substrate is imagined being like a key whose shape is complementary to the enzyme or lock.  The substrate will fit into the active site of the enzyme and will form an enzyme-substrate complex. Once this complex is formed, bonds within the substrate will be affected by the bonds in the enzyme; bonds will break and reform, ultimately forming products. The products will then leave the active site of the enzyme, leaving the enzyme free again to accept another substrate. The diagram below shows how the enzyme works.
A diagram showing how enzyme works
‘Induced fit’ hypothesis
However this is not completely true, by using technique such as X-ray crystallography and computer assisted modeling , we can say that the active site is actually not a perfect fit to the substrate. So when the substrate approach the active site, either the shape of the substrate or the shape of active site will change slightly so they can fit precisely together. In addition, the active site could be modified as substrate interacts with the enzyme. The amino acids which make up the active site are moulded into precise shape which enables the enzyme to perform its catalytic function effectively . The diagram below illustrates the induced fit theory, the shape is different when there is no substrate bonded to it and when there is substrate bonded to it.
A diagram showing the ‘induced fit’ theory
There are molecules that exist which act as enzyme inhibitors. They will disrupt the normal function of the enzyme, preventing it from working so the rate of reaction will decrease, or no reaction at all. There are two forms of inhibitions; competitive and non-competitive inhibitions.
Competitive inhibitors will compete with the substrates for the active sites of the enzyme. This occur when a structure which is sufficiently similar to that of the normal substrate to be able to fit into the active site . As the active site is occupied by the inhibitor, the substrate cannot bind to the active site to get catalysed, so rate of reaction is decreased. However, a competitive inhibition is usually reversible if sufficient substrate molecules are available to ultimately displace the inhibitor .
Non-competitive reversible inhibition
The inhibitor has not got a complementary shape to the active site of the enzyme; it will bind to other parts of the enzyme instead. The binding of the inhibitor to the enzyme will have no effect on the ability of the substrate to bind to the enzyme, but it makes it impossible for catalysis to take place . Unlike the competitive inhibitor, the rate of reaction will not be affected by the concentration of substrate.
Non-competitive irreversible inhibition
This type of inhibitor is non-competitive because it has not got a complementary shape that can fit into the active site of enzyme, so will not compete with the substrate for the active site, and the inhibition is irreversible. Heavy metal ions are typical of this type of inhibitors. They will combine permanently to the sulphydryl (-SH) groups. This could be in the active site or elsewhere  of the enzyme. The metal ions replace the hydrogen in -SH to form -SX. This will alter the structure and active site of the enzyme permanently, therefore enzymes can no longer catalyse the break down of starch.
The diagram above shows the how heavy metal ion, in this case silver, will substitute hydrogen to form -SAg bond. This will alter the shape of active site so the substrate can no longer fit into it to get catalysed. As mentioned above, heavy metal ions are typical of this type of inhibition; copper is a heavy metal ion, so if copper sulphate does inhibit the action of amylase, I can conclude that copper sulphate is a non-competitive irreversible inhibitor.
The collision theory
The collision theory explains how reactions occur. Two particles can only react together if they come into contact with each other. They first have to collide, and then they may react . They may react because colliding particles need to satisfy two requirements to cause a successful collision or reaction.
The orientation of collision
When two particles collide together, they need to have the right orientation when they come into contact for them to react. The diagram below illustrates this.
There are four different orientations of collisions with enough energy for a successful collision to happen. However only collision 1 results in a successful collision, this is because it has the right orientation to collide with the bond which results in a successful collision, the particles in the other three collisions will simply bounce off each other .
Energy of collision
The second requirement for a reaction to take place is that particles must collide with a certain minimum energy, called the activation energy . Without sufficient energy, the two particles will simply bounce off each other after they collide. The activation enthalpy of a reaction is shown below.
Starch and iodine solution
This is a test for the presence of starch in a solution. When iodine solution is added to a solution contatining starch, a blue black colour will form. This is because the amylose, or straight chain portion of starch, forms helices where iodine molecules assemble, forming a dark blue/black color.  This means that when starch is being broken down by the amylase, the amylose will start break down too into smaller units, therefore losing the helics shape around the iodine molecules, the blue-black colour will then start to disappear. I can exploit this characteristic in my experiment to dertermine the end point. Using a colorimeter to monitor the light absorbance, I can determine the rate of reaction as it is the same as how quickly the solution decolourises.