An enzyme is a protein catalyst in a biochemical reaction(biological catalyst). We elaborate further to state a catalyst as a substance that increases the rate of reaction and is not used up in the reaction, the products of the reaction are different substances of the reactant.
Enzymes are positive catalysts speeding up reactions by as much as a hundred million times. They are very selective, they typically affect only one specific reaction. Enzymes are essential for life and an understanding of how they operate is important for medicine and industrial biochemistry.
For enzymes to operate they must be able to make contact with the substrate; the enzyme or substrate or both must be in solution, i.e. in rapid random motion in water. Our cells are about 90% water and water is the medium in which most of our biochemistry takes place.
Basically this is what happens, the active site of the enzyme has a shape closely complementary to the substrate and the substrate locks into the enzyme’s active site. The shape of the active site changes slightly, gripping the substrate more tightly and straining it; an enzyme-substrate complex is formed. The substrate undergoes a chemical change – the new substance (the product) is released from the active site. The active site springs back to its original shape and is ready to receive fresh substrate.
All enzymes are similar in action, therefore the enzymes that work in the liver work with the same conditions and at the same rate as the substitute that will be used in the experiment, that is if all the conditions are similar to that of the liver. These conditions are the pH, temperature and substrate concentration are constant.
Enzymes are practical using enzyme catalase to decompose hydrogen peroxide to determine the effect of enzyme concentration on the rate of enzyme action.
Catalase is present in the cells of fungi, plants and animals. Hydrogen peroxide is poisonous and is a dangerous waste product of many different biochemical reactions that occur in our cells. Our cells produce the enzyme catalase which decomposes hydrogen peroxide to water and oxygen. Catalase operates very quickly – one molecule of catalase can break down 40 million hydrogen peroxide molecules a second. I realized that the catalase greatly speeds up the decomposition of hydrogen peroxide. l discovered the effect of enzyme concentration by altering the catalase concentration.
The requirements (materials and apparatus) that were used are ;a potato, a Petri dish, a cork borer, a blade, hydrogen peroxide solution (20% ),pH buffer solutions, a water bath, thermometer, two identical boiling tubes and a ruler, test tube rack. Fresh potato tissue contains catalase a solid cylinder of fresh potato tissue using a cork borer is removed. Using a sharp one-sided blade I sliced the cylinder into discs 1 millimeter thick and place them in a Petri dish of water. I used different concentrations of catalase by using different numbers of potato discs – 2, 5, 10, 15, 20 and 25 discs for each of the six experiments, I kept the substrate, temperature and pH fixed.
I set up the apparatus including the control. I placed a thermometer in the water bath and maintained 25 degrees heat. I then placed into the water bath a test tube containing a certain number of potato discs ( started with 2),pH 7 buffer and hydrogen peroxide , and another containing potato discs, buffer pH 7, hydrogen peroxide and washing liquid.they were labeled enzyme and control r respectively. The substrate hydrogen peroxide solution (20%); the same volume is used in each test tube. The pH was constant – the same volume of pH 7 buffer was used in both. The temperature was kept constant at 25˚C using a heated water bath.
The control was essential – it was the same set up as the experiment but without the raw potato discs; it was intended to show that only the enzyme is responsible for the rapid decomposition of hydrogen peroxide.
Results of the experiment were as follows;(catalase present): a good height of froth is formed at different speeds/rates as per number of potato discs present in the tube. The higher the number the higher the enzyme concentration and the faster the rate of formation of froth. This is shown by the height of the froth in the tube at a specific time. Control (catalase absent): no froth there were no enzymes present as the washing liquid destroyed them. The graph is plotted with concentration on the horizontal axis represented by potato discs and reaction on the vertical represented by height per minute.
Catalase greatly speeds up the decomposition of hydrogen peroxide and the higher the quantity the faster the action (froth formation). Therefore the higher the liver enzyme concentration the rate of activity in which they work. Example of liver enzymes are; Alanine transaminase (ALT), Aspartate transaminase (AST), Alkaline phosphatase (ALP), Albumin and total protein Bilirubin, Gamma-glutamyl transferase (GGT), Lactate dehydrogenase (LDH) and Prothrombin time (PT).
The experiment was not 100% accurate as the quantities of enzymes were not accurately measured and the rate was not accurately measured. accuracy can be increased if the experiment was done on accurately measured conditions and the rate was measured as per the enzyme action, but all in all it was successful as it gave the general expectation and proved hypothesis on how enzymes are affected by their concentration in their operations.