Concentration Of Substrate Essay Research Paper I

Concentration Of Substrate Essay, Research Paper

I have to plan and carry out an experiment to investigate the way in which concentration of a substrate affects the rate of an enzyme-catalysed reaction. I will need to carry out some background information to find out what may affect my experiment.

Background Information:

An enzyme is a biological catalyst. They speed up the rate of a reaction however they are not affected themselves whilst doing this, this is why they are catalysts. Enzymes are made to be specific, this means that they can have only one substrate that they will work on. Each enzyme has an active site that is where their own specific substrate´s molecule will fit into. Enzymes all work best at an optimum temperature that is usually body temperature at 37C. If the temperature that the enzyme has to work at gets too high, normally 40C it will start to become denatured and therefore no longer work on its substrate as the active site has changed shape. Also enzymes usually work best at an optimum pH level, this is normally 7 because enzymes are proteins which are damaged by very acidic or very alkaline conditions. Most reactions work better at higher temperatures, this is because molecules move around much quicker. This makes the molecules have more chance to collide with the substrate. With more collisions there is more chance of a reaction taking place. This makes the rate of reaction faster. At 40C the enzyme starts to be damaged, this slows down the reaction and by around 60C the enzyme will be completely destroyed.

Plan: Safety/Fair:

For this test I will have to make sure everything is done with safety and fairness. Throughout the whole experiment safety glasses must be worn, as Hydrogen Peroxide can be dangerous if it gets into your eyes. All other Lab rules must be followed also. To make sure the experiment is fair I must make sure nothing is changed for different experiments. I will use the same apparatus for each different experiment and I will make sure the same types of celery and Hydrogen Peroxide are used. The equipment should be kept the same to ensure all results are taken without any advantages or disadvantages. Everything in the experiment should be kept the same apart from the concentration of the Hydrogen Peroxide. Each time the celery will be replaced with another 1g of celery, as it will have been used to react with the Hydrogen Peroxide in the experiment before. The celery will be kept covered as much as possible and will only make contact with the Hydrogen Peroxide when the stopwatch is started. When the celery is measured out on the scales some polythene will be placed under it so that none of the celery is absorbed into the scales. All measurements of celery will be made to 2d.p. This will increase accuracy because the minimum and maximum it can weigh will be 0.995g and 1.005g. If it was measured to the nearest gram, the measurements could be from 0.5g to 1.5g which would be totally inaccurate and would make the experiment unfair as amounts could vary hugely.

Method:

The first thing I will do will be to put on my safety glasses as this test needs to be made safe before anything can be done. I will then get the equipment I need for the experiment. The equipment I will use is a water basin, a conical flask, a bung, a delivery tube, a measuring cylinder, a syringe, a spatula and a stopwatch. Then I will collect the concentration of Hydrogen Peroxide I will need for the experiment I will be doing; also 1g of celery will be measured out on the electric scales, this will be measured to 2 decimal places as that is what the scales measure in. This is accurate enough for the experiment I will do. I will fill the basin with water next and then fill the measuring cylinder as well. The measuring cylinder will be placed upside down in the basin still full of water, making sure that no water is escapes so that the experiment is fair. I will then stick the liquidated celery to the side of the conical flask; this will be done using a spatula. The next thing that must be done is to put the delivery tube and bung together and place the delivery tube under the measuring cylinder so that any gas pushed through will go into the measuring tube. 5cm of Hydrogen Peroxide will then be measured out using a syringe. This will then be put into the conical flask very carefully; making sure that it doesn´t mix with the celery, then the bung will be put into the conical flask. If the two mix I will have to wash out the flask and start again with new hydrogen peroxide and new celery, as the reactions will have started without the amount of oxygen being recorded. The measuring tube will be kept in place by hand and then simultaneously the flask will be shook, mixing the celery and Hydrogen Peroxide, and the stopwatch will be started. Measurements will be taken from the side of the measuring cylinder every 30 seconds and noted down. All measurements will be made as precise as possible to keep the experiment accurate and fair. Preliminary Work:

I chose to use the different apparatus in my experiment from preliminary work I have done. I could have used liver instead of celery but liver reacts too much too quickly to be able to record the results with any accuracy. This is because it has too many catalaes, so the reactions are made a lot quicker. Once I had chose celery I had the choice of boiled celery