There are many factors that affect enzymes:
Temperature: Normally increasing the temperature increases the rate of many chemical reactions, and a fall in temperature slows a reaction down. Whereas with enzymes they denature above 50ºC, being proteins and stop working. This is because their shape is changed and thus cannot combine with other substances. The temperature at which an enzyme works best is called its optimum temperature, and in humans it is at 37ºC.
PH: Acid and alkali conditions affect the chemical properties of proteins (inc enzymes). Enzymes work ideally at particular level of acidity or alkalinity. Also, an enzymes best pH is called its optimum pH. However although, the conditions of acidity and alkalinity affect enzymes behavior, they are normally reversible.
Concentration: The higher amount of substrate to combine with, the faster the reaction due to the theory of successful collisions the more successful collisions the faster the rate of reaction. Lowering the amount of substrate reduces the rate due to less frequent collision between enzyme and itself.
Surface area: If the size of the enzyme is larger, then breaking it up will increase the rate of reaction, as there are more successful collisions with the substrate. Due to the fact of the particles having more area to work on.
Prediction
I believe that the higher the concentration of the substrate the faster the reaction and the more oxygen produced this is because there will be more frequent and successful collisions between enzymes and substrate. Therefore more oxygen produced when reacted. Therefore the more hydrogen peroxide, the higher the rate of reaction, and the less amount of hydrogen peroxide the slower the reaction. The graph will be a straight line through the origin as , will at 0cm of hydrogen peroxide no oxygen will be produced, there will only be water and potato in the test tube.
Fair Test
Temperature will have to be kept at a constant throughout the experiment, so that it does not affect the way in which enzymes behave. As higher temperatures can cause the enzyme to denature and stop working ad thus stopping the whole temperature.
Size of each and every potato is very important; each and every piece of potato must be kept the same dimensions. This is because a longer potato increases surface area, and thus increases rate of reaction as there are more collisions and vice versa.
pH can easily affect the experiment and therefore make sure there are not any acidic or alkaline substances around.
Make sure you use different test tubes for each individual experiment, so that it does not affect the concentration of each substance.
Make sure you are quick in placing the bung in to the delivery tube, so that there the gas does not escape.
Make sure the delivery tube is always under the water and the test tube.
From the preliminary experiment was found that much of the oxygen was trapped because f the way I was holding the test tube which made the delivery tube bend, and trap it.
The same scales and apparatus will be used, for each experiment, as measurements and quality of apparatus are all different, and thus may have different effects when using in an experiment.
Safety
Use goggles to protect the eyes, from hydrogen peroxide.
Wear gloves when handling hydrogen peroxide, as it is corrosive.
Make sure the stand being used is not liable to fall down.
Remove bags from the area of experimentation.
When using the scalpel, always take care, in cutting the chips. Always cut on a white tile, and hold them so that they will not move whilst cutting them.
When using the cork borer, make sure your hand supporting the potato, is not in the way.
Apparatus
Stand, Boss, Clamp
Test Tubes
Scalpel
White tile
Stop Watch
Delivery Tube
Bung
Measuring Cylinders
Potato
Hydrogen Peroxide
Distilled Water
Ruler (mm)
Diagram
Method
- Set up experiment as in diagram
- Place the potato on the white tile, and using a cork borer, extract 5 pieces of potato.
- Place the 5 pieces of potato on the white tile, and measure their length.
- Using a scalpel make each length 4cm.
- Get 5 test tubes and label them 1-5, and using the table below, pour the correct amount of solution (using a measuring cylinder into them) regarding the test tube number.
- Then start with test tube 1, and put a piece of potato in the test tube, start stopwatch, and replace the bung. After 30-second intervals, measure the volume of oxygen produced, by checking the amount of water in the measuring cylinder.
- To test for oxygen, take a glowing splint and check if it relights when it meets oxygen from the measuring cylinder. Remember though to put you thumb over the measuring cylinder carrying the oxygen.
- Repeat stage 6 with test tubes 2-5, and record results in a table.
Obtaining Evidence: The Results
I will also repeat the experiment twice, so I can calculate average results, which will be more accurate. These results were obtained by my safe method, and seem to follow the hypothesis theory. I will tabulate the results with the same number of decimal points, to make the experiment easier to analyze.
Average Results
Analysis and Conclusion
Graphs of the average results of the experiment have been produced. There are five graph lines of best fit, which show a clear pattern.
The steepest graph was the concentration of hydrogen peroxide and water at 50:0, which was all hydrogen peroxide. This agrees with my prediction, and theory and this shows that my experiment was accurate. The line of best fit went through or just edges past the points of concentration 50:0. The reason for the steep line is due to the fact that, as there were more hydrogen peroxide particles present, then there would be a faster rate of reaction as there would be more successful reactions, as the catalase particles would react with the particles of hydrogen peroxide. Therefore as the concentration of hydrogen peroxide decreases, the rate of reaction decreases, as there is now less of a chance of a particle of catalase colliding with the particles of hydrogen peroxide, as there aren’t as many. Thus my graph is accurate as, the gentler slopes are those with less concentration of hydrogen peroxide, thus having a low rate of reaction. This is because of the decrease in chance that a hydrogen peroxide molecule will collide with a catalase molecule. The results are also accurate as it also shows the order in which the line of best fit get gentler, is in fact correct.
Observations, which took place, were the fact that the gas produced was oxygen, this was found out by capturing oxygen in a measuring cylinder, with your thumb. Then relighting a glowing splint, blowing it out, then carefully place it in the test tube, with the oxygen init, and it relights.
The rate at which the bubbles occurred was quicker when the concentration of hydrogen peroxide was at it’s highest. The experiment was more vigorous, this because there were more hydrogen peroxide particles colliding with the catalase particles.
There were two anomalies found which are both circled, this is probably due to experimental error, however they all graphs clearly show that rate of reaction decreases as the concentration of hydrogen peroxide decreases, such as the time during placing the delivery tube in to the measuring cylinder. The way the measuring cylinder was held, caused the delivery tube to bend, and thus stopping, the oxygen gas given off from being collected.
Therefore in conclusion rate of reaction and concentration of hydrogen peroxide are proportional to each other, as the concentration of hydrogen peroxide increases, the rate of reaction increases, as the concentration of hydrogen peroxide decreases, the rate of reaction decreases.
Evaluation
My graph and my results both agree with my prediction, however there are two anomalies, which show that my results and method were not accurate enough. But they both show that as concentration of hydrogen peroxide increases so does the rate of reaction. My prediction is correct.
There may have been many experimental errors:
Firstly, the length of all potatoes pieces may not have been accurate, due to the poor way in which I used the ruler, or the smaller less accurate scales. Another factor that could have affected the experiment is the time taken during replacing the bung, and the starting stopwatch. Also, the way in which the delivery t rube was held, made it bend and thus stop gas from
To make the experiment a success, one could have used to people so that the process in replacing the cap is faster and thus less oxygen is loss. Another factor in which could have helped my experiment is the apparatus used, if a more accurate ruler, which measures in millimeters was used to give the length of potato.
Also to improve my experiment, I would have taken more result, to improve the accuracy. To further my investigation, I would probably investigate the factors of surface area, and temperature. This would give me a wider perspective on enzymes and thus I could analyze it further.
