Enzyme Catalase INTRODUCTION The enzyme catalase speeds up the decomposition of Hydrogen Peroxide into water and oxygen as shown here, 2H2O2——————-*2H2O+O2. It is one of the fastest known enzymes and its turnover number is 6 million, which means the number of substrate molecules which one molecule of the enzyme turns to products per minute. This can be demonstrated by putting a piece of liver into a beaker of Hydrogen Peroxide, the fizzing shows a demonstration of the enzyme in action. AIM My aim is to examine how the concentration of the substrate hydrogen peroxide affects the enzyme catalase. INVESTIGATION I am going to investigate the effect of varying the substrate concentration on enzyme catalase.
I am going to use 8 different concentrations and record the time taken to collect 20ml of gas in the gas syringe. I will repeat all the 8 concentrations twice so I can see if they match, spot out any anonymous results and also I can work out the average time it takes to produce 20ml of gas at the certain concentrations. I will vary the concentrations by increasing and decreasing the amounts of Hydrogen Peroxide and water. PLAN First of all I will ensure I have enough enzyme solution for the whole experiments so the enzyme solution is standardised. With the results I get I will try to work out the Vmax. I will do this experiment at room temperature so the enzymes get enough kinetic energy to collide.
I will need 80ml of the enzyme solution because I will use 5ml for all of the experiment and I will do 8 different concentrations and I will repeat this concentrations twice so that is 5x8x2= 80. First of all I will set out the equipment as I will show in the diagram then I will cut some pieces of liver, which is the source of the enzyme. Then I will grind the pieces of liver with the mortar and pestle, which will have sand and Di ionised water (which is water with no H ions in it its PH is neutral). The sand will help cut open the cells of the liver. I will take a funnel with glass wool in it, I chose glass wool rather than filter paper because the catalase could have been adsorbed by the filter paper. Then I will add 5ml of the enzyme catalase to the conical flask and for the substrate concentration of 10% I will add 2ml of Hydrogen Peroxide and 18ml of water (18+2= 20, I will always use 20ml) every time I when I will increase the concentration by 10% I will increase the H2O2 by 2ml and decrease the H2O by 2ml.
I will time how long it takes to produce 20ml of gas in the gas syringe. I chose the gas syringe rather than to count the bubbles produced in a measuring cylinder because it is easier to use, the results will be more accurate and the gas syringe reduces the possibility of gas escape. I will tabulate my results and highlight them in some way so they are visible I will interpret my results in to a line graph. I will also added a line of best fit to the results on the graph and with the results I get I will work out the Vmax. Here is a blank copy of my results table, which I fill in later when I get my results. FAIR TEST To make my experiment a fair test I need to ensure that all the variables must be kept the same for all the experiments except for the concentration of Hydrogen Peroxide.
I will accurately measure out the Hydrogen Peroxide and enzyme solution using a pipette and measuring cylinder. I will use glass wool rather than filter paper because if I use filter paper then the catalase could be adsorbed by the filter paper, which will no longer make my experiment a fair test. I will time how long it takes to produce 20ml of gas by using a stopwatch accurately. For each concentration I will make sure that there is no excess catalase or substrate in the measuring cylinders I use by cleaning them. I will hold the rubber bung connecting the conical flask and the gas syringe so it does not open and let out any gas. PREDICTION I predict that the more the concentration of substrate the faster it will be to produce 20ml of oxygen if you increase the concentration there will be a higher chance of collision between the particles, but there will come a point where all the active sites are full and the rate should go constant.
Enzymes such as catalase are protein molecules. They are used to speed up specific reactions in the cells. They are all very specific as each enzyme just performs one particular reaction. Once the amount of substrate molecules added exceeds the number of active sites available then the rate of reaction will no longer go up. The graph should look like this, I know this from background scientific knowledge, from my notes and textbooks.
SAFETY ASPECTS The safety precautions that I will consider taking are that I am going to ensure that I wear goggles because Hydrogen is a strong oxidising agent and if it gets into my eyes it could be irritating and eat away at my cornea, corneal burns can occur rapidly. I will also make sure that the Hydrogen Peroxide does not come in contact with my clothes or hands so I will wear an apron and gloves if the Hydrogen Peroxide does come in contact with my hands, which will cause whitening of the skin and stinging. I will immediately wash my hands thoroughly with water. Hydrogen Peroxide is a strong deodorizing and bleaching agent. It has a characteristic pungent odor.
If anyhow I swallow the Hydrogen Peroxide I will drink water straight away to dilute and immediately contact a physician. If I break any apparatus I will inform the teacher straight away and I will clean the broken apparatus. APPARATUS LIST ? Scalpel and chopping board ? Pipette ? 4 measuring cylinders, (3) 100ml (1) 10ml ? Conical flask ? Gas syringe ? Mortar and pestle ? Glass wool ? Rubber bung with delivery tube ? Retort stand with clamp and boss ? Stopwatch ? Sand ? Spatula ? Hydrogen Peroxide ? Di ionised water ? Source of enzyme (liver) I used these apparatus because it was the equipment available and suitable for my experiment. I used the gas syringe rather than to count the number bubbles produced in a measuring cylinder because it is more easier and accurate and it also gives a less possibility of gas escape. I used the stopwatch because it is accurate to measure the time rather than counting the time yourself.
I used the spatula to pick up bits of the sand and put in the mortar and pestle in which I was grinding the pieces of liver. I used the scalpel to cut the pieces of the liver and I cut the pieces on the chopping board so I dont cut into the table that I was working on. I used the mortar and pestle to grind the pieces of liver. I used the glass wool rather than filter paper because the catalase could be adsorbed by the filter paper, which will no longer be a fair test. METHOD First of all I ensured I had enough enzyme solution for the whole experiments so the enzyme solution was standardised, so if incase I am in between an experiment and the enzyme solution finishes then if you make the solution again you might not get the right concentration, so the experiment will not be a fair test.
I used pipettes to get the solutions and I accurately measured the amounts by using measuring cylinders. I needed 80ml of the enzyme solution because I used 5ml for all of the experiment and I done 8 different concentrations and I repeated these concentrations twice so that is 5x8x2= 80. First of all I set up the equipment as shown in the diagram then I cut some pieces of liver, which was the source of the enzyme. Then I grinded the pieces of liver with the mortar and pestle, which had sand in it and Di ionised water (which is water with no H ions init its PH is neutral). The sand helps cut open the cells of the liver. I then took a funnel with glass wool in it, I chose glass wool rather than filter paper because the catalase could have been adsorbed by the filter paper.
Then I added 5ml of the enzyme catalase to the conical flask and for the substrate concentration of 10% I added 2ml of Hydrogen Peroxide and 18ml of water (18+2= 20, I alw …