РефератыИностранный языкInInvestigating Enzymes Essay Research Paper Research Enzymesexist

Investigating Enzymes Essay Research Paper Research Enzymesexist

Investigating Enzymes Essay, Research Paper


Research Enzymes


exist in all living things. They are composed of polymers of amino acids and


are produced in living cells. Each cell contains several hundred enzymes, which


catalyse a vast number of chemical reactions. Enzymes are known as Biological


Catalysts as they dramatically increase the rate at which reactions occur


within living organisms, without being ?used up? or effecting the reaction in


any other way. Enzymes catalysis saves the need for an increase in temperature


in order to speed up reactions within living things. Such an increase in


temperature would be lethal to the organism. In


this investigation I intend to explore the one of the factors that effect the


rate of enzyme catalysis. My research from textbooks and the Internet suggests


that this depends on several factors; temperature, pressure, pH and


concentration. After research and careful consideration, I have decided to


first look at how a change in temperature could affect the rate of reaction. In


order to design a suitable experiment and make a credible prediction, I must


first explore more closely how temperature is likely to affect the rate of


catalysis. Enzymes are specific – they only control one type of reaction;


therefore I must use one specific enzyme in my experiment, in order to find a


clear way of measuring the rate of reaction. Although they are specific, all


enzymes work in a very similar way and have similar properties. They are all


globular proteins and are all biological catalysts, they increase the rate of a


given reaction without being used up and their presence does not change the


nature of the reaction or the end product. Enzymes work by having an active


site, made from amino acids. Here, substrate molecules will bind with the


enzyme (and other substrate molecules if necessary) and a reaction takes place.


The enzyme itself is not affected and releases the new chemical after the


reaction. After release of the end product, more substrate molecules can bind


with the active site. Enzymes


can catalyse anabolic reactions or catabolic reactions (involved in breakdown).


The diagram above shows an anabolic reaction. In a catabolic reaction, the reverse


would happen. Using


the information gained here together with my knowledge of kinetic theory, it is


possible to understand how temperature affects the rate of reaction. Kinetic


theory states that when a substance is heated, energy is given to the particles


and they speed up. Therefore when heat is applied to an enzyme and substrate,


the particles speed up, increasing the rate at which they bind with each other.


This would suggest that the rate of reaction should increase as the temperature


is increased. This is not quite true, as there is a limit to the temperature at


which an enzyme can work because excessive heat causes an enzyme to become


denatured and stop working. Also, there is a minimum temperature at which an


enzyme can function. Every chemical reaction requires activation energy in


order to get started. Although enzyme catalysis greatly reduces this, some


energy is still required. Because of this the reaction is still unable to


happen below a given temperature (this varies depending on the type of enzyme


and reaction, as does the maximum temperature). If warmed to above the


activation temperature, an enzyme will work again as normal. A denatured


enzyme, however, is damaged and will not work again even if cooled below the


optimum temperature. Prediction I


predict that the rate of reaction will increase as the temperature increases


until the reaction reaches an optimum temperature. Above this optimum


temperature, the rate of reaction will fall to zero very quickly, as the enzyme


denatures. I must now conduct an experiment to test my prediction. I will do


this using the enzyme catalyse. Catalyse is found in most living organisms. It


speeds up the catabolic reaction, which breaks down hydrogen peroxide into


oxygen and water. Apparatus Using


my information on catalyse, it is clear that one of the products of the


reaction is oxygen. Therefore to measure the rate of reaction, I could measure


the rate at which oxygen is produced. For this experiment I will need: Leek


as the source of catalyse Hydrogen


peroxide A


water bath in which I can heat both enzymes and substrate Thermometers


to ensure both liquids are at the correct temperature Measuring


cylinders in order to measure the amount of oxygen produced, as well as


the amount of yeast/hydrogen peroxide used A


timer to enable me to work out the rate at which oxygen is produced A


basin of water Conical


flask in which the reaction will take place Bung


and delivery tube Method To


test my prediction I will heat the catalyse and hydrogen peroxide to a given


temperature and allow them to react in the conical flask, starting the timer at


the beginning of the reaction. The oxygen given off will pass through the


delivery tube and bubble up into the measuring cylinder, which will be set full


of water in a basin. I will allow the reaction to continue for a set period of


time before using

the measuring cylinder to measure the amount of oxygen


produced. The results will then be recorded in a table, and then graphed after


the experiment has been conducted at a satisfactory amount of temperatures. My


preliminary experiment suggests that suitable quantities to use would be 20cm3


hydrogen peroxide and 10cm3 leek, timed over a period of one minute


during the reaction. I am now able to perform the experiment at a range of


temperatures between 0degrees and 80degrees. If the rate of reaction is still


above zero beyond 80degrees, I will continue the experiment for higher


temperatures. My research suggests however that most enzymes become denatured


before 80degrees. Fair Testing To


make sure this experiment is a fair test, the only factor I must vary must be


temperature. This means that I have to keep the concentrations, pressure and pH


of the substance constant throughout the experiment. In order to ensure


accuracy, I will conduct the experiment three times for each temperature and


take a mean result to plot on the graph. The exact quantities used must first


be determined by a preliminary experiment. Results Conclusion Several


points can be drawn from the results of this experiment. The first is that the


graph is very similar to that of my prediction. It clearly shows an optimum


temperature at which the catalyse will work, with an increase/decrease either


side. I was surprised at the way the rate of reaction slowed above the optimum


temperature. I had expected there to be a very sharp decline as soon as the


optimum temperature was surpassed. This was the case, but the rate of decline


slowed at one point, which contradicts my research. This may be due to an


inaccuracy in my experiment, as my research suggests that enzymes fail to work


after becoming denatured. Another


thing that can be learned from the results is that the speed at which the rate


of reaction increases as the temperature rises seems to become greater. Between


10degrees and 20degrees the increase is equal to the original rate of reaction,


whereas between 20degrees and 30degrees, the increase is double the original


rate of reaction. However, the increase in the rate of reaction seems to slow


again between 30degrees and 40degrees. This could be for several reasons; that


this is exactly what is supposed to happen and the rate of reaction does slow


again when close to the optimum temperature, or that the optimum temperature


lies somewhere between 30degrees and 40degrees and that the rate of reaction


has reached it?s optimum temperature and is slowing again by the time the


temperature reaches 40degrees. In any case, I would have to investigate this


further in order to reach a firm conclusion as to the reason this graph appears


to show slowing of the increase in the rate of reaction between these points. I


believe these results can be explained in the same way as my prediction, as the


prediction was on the whole correct. Because the particles move faster as heat


is applied, they bind with the enzymes quicker and more often so the rate of


reaction speeds up. When the optimum temperature is surpassed, the enzymes


begin to denature and cease to function, causing the rate of reaction to slow. The


reaction will never stop completely, as hydrogen peroxide will break down


naturally, even with no working enzymes present. Evaluation The


data obtained in this experiment supports my conclusion well, although there


were some results and trends that I couldn?t explain. This may have been due to


inaccuracies in the way the experiment was performed, or that I need to further


my knowledge in order to explain the results. I


am convinced that the results show there is a correlation between the increase


in temperature and the increased rate of reaction. This correlation would have


been easier to work out had my measurements been slightly more accurate. The


accuracy of these measurements could be improved by the use of a burette


instead of a measuring cylinder, as it is a more precise piece of equipment and


there are fewer margins for error. Another source of error may have been in the


water baths, as they were supposed to be set at fixed temperatures to heat up


the substances. One had to be very careful that the substances did not exceed


their planned temperatures of there was danger of denaturing. The experiment on the


whole was a success, but it could be improved by the use of more accurate


equipment and better organisation. Several assumptions had to be made in this


experiment. When such assumptions are made, further work needs to be carried


out to check these assumptions. I had to assume that all enzymes worked in the


same way, but further work could be done with different enzymes and reactions


to check this. Through the experiment, I measured the rate of reaction at


10degrees intervals. I think that further work should be done between 30degrees


and 40degrees in an attempt to find the exact optimum temperature for the


enzyme catalyse. Work between these temperatures would allow me to plot a more


accurate graph and explain the apparent slowing in the increase of the rate of


reaction between these two temperatures in my current results.

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