Is there a relationship between the quantity of enzymes and the rate of reaction with the substrate? Hypothesis Using my scientific knowledge my hypothesis is that as the quantity of enzymes increases so will the rate of reaction. Reasons for this hypothesis I am basing my hypothesis on a hypothesis known as the 'lock and key hypothesis.' It explains that when an enzyme substrate complex forms by means of a spontaneous reaction the substrate fits into the active site like a key fits a lock. It is known as a spontaneous reaction not because it happens spontaneously but because it requires initial energy in order for the reaction to take place and the products have less energy than the reactants. An active site occurs in the enzyme because a few of the amino acids on the surface of the 3 d molecule fold inwards thus creating an indention in the enzyme.

The 'lock and key hypothesis' uses this analogy due to the fact that only one substrate fits one particular active site. This is because simply the substrate and active site both contain certain elements that will only product certain temporary bonds with particular other elements. However, despite the 'lock and key hypothesis' theory being very strong it was discovered that there was a flaw in the theory. It was realised that small molecules like water could enter the active site.

This caused for a refinement in the theory to be made. The refinement was the cause of the discovery that when a substrate enters an active site small changes in the active site have to occur before the spontaneous reaction can take place. This background information is what I am using as a foundation for my hypothesis. This is because as I increase the surface area I will be exposing more enzymes, therefore more active sites are made available for the substrates to be pulled towards them.

I will be able to see the rate of reaction increasing because as I increase the surface area more oxygen will be released due to the catalytic reaction. However, if I was looking at increasing the concentration of the substrate rather than the quantity of enzymes I would find that there would be a limit to the amount in which the rate of reaction could increase. Therefore on the graph after a certain amount of positive correlation the line would stay at the same level. This is because all the active sites would be being used. To consolidate my own knowledge of this topic I used the website web to be changed In my particular experiment I am going to change the surface area of the potato five times. To give a range of observations I will start with a surface area of 5.

9 cm^3. Each observation I will get that surface area again and cut it in half and keep on doing so until I have done five experiments. Variables to be kept the same Variable How I will keep it the same Mass of potato Use the same borer to extract the potato from and measure it to the nearest mm each observation. Volume of hydrogen peroxide Accurately measure out 25 ml of hydrogen peroxide each observation. Concentration of hydrogen peroxide Look carefully at the bottle to ensure that I am using the same concentration. Temperature Use a thermometer to test the temperature of the experiment.

Time Use a stopwatch accurately and allow the same amount of time for each experiment. Why is it important that I control these variables? I know that, for example, temperature affects enzymes the rate of reaction. Above the optimum temperature of about 40 degrees (where they work fastest) the rate decreases as more and more of the enzyme molecules denature. The thermal energy breaks the bonds holding the structure of the enzyme together and so the enzyme and also the active site lose its shape and looks like a random coil. At very high temperatures this is irreversible and so the enzyme has become de-natured. Below the optimum temperature the rate also slows down as the enzymes are becoming inactive however this is irreversible.

This means that is important I keep the temperature the same as if I increased it by a couple of degrees the volume of oxygen produced would double and if I lowered the temperature the volume of oxygen produced would be less. Measurements The measurements I will use are as follows: o Ml for the hydrogen Peroxide o Mm for the length of the potato (as part of the surface area formula) o Cm cubed for the surface area to 1. dpApparatusBelow is a list of apparatus I will use for the experiment. o Water o Test tube so Trough 2 potatoes 1 tile o Borer with a 1 cm diameter o Delivery tube and bun go 2 measuring cylinder so Hydrogen Peroxide Stop Watch Water bath o thermometerDiagramPotatoBungTest Tube Hydrogen Peroxide Delivery Tube Measuring cylinderWaterOxygenWater trough Plan of procedure o Get all required apparatus out. o Wearing safety goggles measure out accurately 25 ml of hydrogen peroxide and pour into a test tube.

o Pour 25 ml of hydrogen peroxide into one test tube, this is your control. o Carefully put the test tube into the water bath with a thermometer in it and leave it there until it reaches 35 degrees Celsius. o On the white tile, use the borer to collect the potato by pushing it in and twisting then pulling it out of the potato. o Cut the sample of potato with the knife to 3. 5 cm. o Use the formula 2 pi r^2 +pi dh to work out the surface area.

o Fill the trough three quarters full with water and the measuring cylinder to top. o When the hydrogen Peroxide has reached 35 degrees Celsius get it out of the water bath. o Put the potato in, start the stopwatch put the bung in the top and the delivery tube into the measuring cylinder under the water. o After two minutes record how many cm cubed the water in the cylinder has gone down by, (this is the amount of oxygen produced. ) o Record your results. o Repeat steps 1-9 twice for each surface area you do.

Except, each time cut the 3. 5 length of potato in half so that you are equally increasing the surface area. o Work out the new surface area by adding on the area of the circle times by the number of new faces you are exposing. o Repeat any anomalous results. Preliminary investigation. When planning an investigation like this it is important that I make sure that my results will be as accurate as possible.

In order to achieve this I decided to carry out a preliminary investigation to ensure that two minutes would be a sufficient time to allow a good proportion of the reaction to take place and also that 37 degrees Celsius would be a good temperature for the hydrogen Peroxide. Using the above method with the 3. 5 length cut into four disks I carried out the investigation twice. Once at room temperature and then again at 37 degrees Celsius.

At 18 degrees Celsius the reaction produced 2 cm cubed of oxygen in two minutes. At 35 degrees Celsius the reaction produced 4 cm cubed of oxygen in two minutes. This preliminary work evidential ly proved helpful as two minutes was enough to allow sufficient amount of the reaction to take place. Also, carrying out the reaction at a higher temperature meant that the enzymes could work faster and produce more oxygen in the same amount of time.

This is because at 37 degrees Celsius (body temperature) enzymes are at their optimum. Too high the temperature and the enzymes would become denatured due to their structure and the fact that they are proteins. I initially tried to heat the hydrogen peroxide to 37 degrees Celsius but it was to hard to be accurate with the thermometer so that it was exactly 37 degrees Celsius. I then decided that 35 degrees Celsius was a more rounded number to heat the hydrogen Peroxide to. Reliability Reliability means that if anyone repeated my investigation they would be able to see a similar pattern. In order to make my results more reliable I would have to repeat it more times to get results which show a trend.

This would mean that the 'mean' would be more reliable. I will also repeat any anomalous results. Safety Safety is an important aspect of any investigation. To make my experiment as safe as possible I will: o Wear a lab coat and safety goggles when handling Hydrogen Peroxide. o Wash hands after the experiment as Hydrogen Peroxide is corrosive. o Always walk in a laboratory.

o Tuck stools under so that no-one trips over them. o Work in a neat and tidy area. o Use the borer onto a tile not your hand. It is sharp! o Be careful when using the knife and carry it with the blade facing down. Finding the mean Finding the mean is an accurate way of finding the average and will mean that I can plot these on my graph to see if there are any trends.

To work out the mean values I added together all the results for the specific surface area and divided this by the number of trials I had done. For example to find the mean for surface area 5. 9: 3. 6 + 2. 6 + 6. 2 + 1.

6 + 3. 6 = 17. 617. 6: 5 = 3.

52 = 3. 5 (1 dp) Anomalous results are results that seem unexpected or do not seem to fit the model. These were written in red. However, just because a result does not seem to fit within a smooth line does not mean it is anomalous, it could possibly be inaccurate.

I have identified anomalous results by highlighting them in red. These certain results are anomalous because they do not coincide with the range of results for a specific surface area and were therefore unexpected. Conclusions I can make from the graph. From my results I can conclude that as the surface area increases so does the rate of reaction (the volume of oxygen produced. ) The graph shows positive correlation and that y increases at an increasing rate. The equations y = mx^2 or Y = mx^3 could explain the relationship that Y is proportional to X^2 or X^3.

Therefore I can observe that as surface area of the potato increases so does the volume of Oxygen. For example when the surface area was 5. 9 cm^3 the amount of oxygen produced, on average, was 3. 5 cm^3. When the surface 6. 7 cm^3 on average 5.

3 cm^3 of oxygen was produced. This shows that the rate of reaction is increased as the faster the hydrogen peroxide is being used the quicker the oxygen is produced (faster rate of reaction. ) This is because I was exposing more enzymes, by increasing the surface area this resulted in more active sites being made available. Overall the results prove my hypothesis: as the quantity of enzymes increases so will the rate of reaction. Reliability of Conclusion My conclusion is reliable because on the whole my results are accurate and seem to follow a pattern except for the anomalous results which contradict my hypothesis. I also think that apart from temperature the controlled variables were easy to control and so some one would be able to repeat my experiment and get results with the same range as me.

I think that the surface area of 5. 9 cm^3 was the results that were less reliable as I had two abnormalities, this meant I had to repeat them but still include the anomalous results when calculating the mean. I think this limits the overall accuracy and reliability. The majority of results prove my hypothesis.

In my evaluation I will explain the reasons behind certain abnormalities. Evaluation of procedure My procedure was effective except for certain areas. It was these weaknesses in the procedure that I believe caused my anomalous results. o The time varied between starting the stopwatch and putting the bung in to the measuring cylinder to start measuring the volume of oxygen being produced.

This meant that the results could have been inaccurate explaining why certain results were much lower than others in the same surface area. To overcome this I would need to have more people working in the practical, perhaps 3, so that everything could happen at the same time. o We changed the type of potatoes it could be possible that one type contain a larger amount of enzymes. If I were to repeat this experiment I would ensure that I only used one particular type of potato. o When putting the potato into the hydrogen peroxide occasionally the faces stuff together this meant that more enzymes were not being exposed.

In future it would be more accurate to put the faces in quickly one by one. o The borers had slightly different diameters therefore changing the surface area slightly. If I were to improve the experiment I would ensure that the same borer was used all the time. o The temperature of the room varied slightly on different days, affecting the rate of reaction. It would have been better if we had done all the experiments on the same day when the temperature would have stayed more constant. A difference of one degree could double the amount of oxygen produced.

o The water bath was unreliable, this was an equipment error. The results would be even more reliable if I'd had used a more accurate water bath. o Without realising it occasionally I held onto the tube whilst the reaction was taking place. This is not very scientific as the heat from my hand makes the gas in the tube expand thus making it look like more oxygen has been produced. I would need to make sure that if I repeated this experiment that I never held onto the tube whilst the reaction was taking place. Evaluation of results.

To improve the reliability of my results, I would: o Do more repeats of each surface area so that I could find a more accurate mean. o Include more in between values for the surface area this would affect my graph and I would be able to look even closer at the proportional relationship. I would also get a more accurate line of best fit and this is important with a curved line. o Better equipment, the investigation would benefit greatly with a more accurate water bath so I could make sure that I got the same temperature every time.

Further Work Ideally from this investigation I would like to repeat this investigation and expand it by doing more values of 0-5 as here I have a lack to results for the line of best fit. I would also like to do more in between values. This would mean that I got a more accurate graph as I would have a more scientific line of best fit and more evidence to support it.