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Factors effecting enzyme activity

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Introduction

Biology Coursework Factors effecting enzyme activity Aim: To investigate the effect of temperature on the rate of catalase activity. Enzymes are proteins that act as catalysts, which are made in the cells. A catalyst is a chemical substance that speeds up a reaction but does not get used up in the process. Enzymes can be used over and over. There are two types of enzyme reactivity, these are called anabolic and catabolic reactions. An anabolic reaction is where large molecules are built up from smaller molecule. A catabolic reaction is where reactions split large molecules into smaller ones. Enzymes work by a method called the lock and key method: Basically it works by the enzyme meeting the substrate and they both fit together well to make an enzyme-substrate complex. This works well because enzymes have a definite three dimensional shapes which is complementary to the shape of the substrate. In the enzyme-substrate complex, the substrate attaches to an area on the enzymes known as the active site. The enzyme is then free to react again with any available substrate. Catalase can be found, not just in humans but in potatoes, apples and the liver. During my preliminary work, I will be investigating which of these gives off the most oxygen. The one which gives off the most oxygen will be the catalase that I use during my experiments. This way it will give me the best results as it has produced the most oxygen. The rate of catalase activity can be measured by measuring the amount of oxygen given off by reacting catalase with hydrogen peroxide. Hydrogen peroxide is a harmful by-product of the process of cellular respiration especially if it builds up in concentration in the cells. The oxygen could be collected by using an upside down measuring cylinder. Hydrogen peroxide is a by-product of fatty acid oxidation. White blood cells produce hydrogen peroxide to kill bacteria. ...read more.

Middle

After every 10 seconds record the amount of oxygen that has been produced. Record your results in a table like the one below and repeat three times for accurate results. Below is a blank results table to show how I am going to record my results: Temperature/�C Time/secs Oxygen produced (1)/cm� Oxygen produced (2)/cm� Oxygen produced (3)/cm� Average Obtaining Evidence: During the biology coursework day, I carried out a series of experiments to investigate how temperature affects the rate of catalase activity. Using my method I got the results below: Firstly, I am going to measure the rate of reaction at 20oC. However, the closest that I could get to 20oC was 21oC as the temperature fluctuated quite a bit. Here is the table of results that I obtained from doing that experiment: Temperature/�C Time/secs Oxygen produced (1)/cm� Oxygen produced (2)/cm� Oxygen produced (3)/cm� Average 21.0 10.0 28.5 28.3 28.9 28.6 21.0 20.0 34.5 33.5 33.1 33.7 21.0 30.0 35.6 35.1 35.5 35.2 21.0 40.0 36.6 36.1 35.6 36.1 21.0 50.0 36.8 36.3 36.7 36.3 21.0 60.0 37.0 36.3 35.7 36.3 I then increased the temperature from 21oC to 29oC, to see whether increasing the temperature affected the rate of reaction, recorded my results in this table: Temperature/�C Time/secs Oxygen produced (1)/cm� Oxygen produced (2)/cm� Oxygen produced (3)/cm� Average 29.0 10.0 33.1 34.7 35.0 34.3 29.0 20.0 35.0 35.2 37.1 35.8 29.0 30.0 35.5 35.3 37.5 36.1 29.0 40.0 35.8 35.4 37.8 36.3 29.0 50.0 36.0 35.5 38.0 36.5 29.0 60.0 36.0 35.5 38.1 36.5 I then increased the temperature again to 38oC to see how increasing the temperature affected the rate of reaction, here is a table to show my results: Temperature/�C Time/secs Oxygen produced (1)/cm� Oxygen produced (2)/cm� Oxygen produced (3)/cm� Average 38.0 10.0 31.0 31.0 31.0 31.0 38.0 20.0 31.1 32.0 32.5 31.9 38.0 30.0 31.2 33.5 33.0 32.6 38.0 40.0 31.3 34.0 33.5 32.9 38.0 50.0 31.6 34.1 33.6 33.1 38.0 60.0 31.6 34.1 33.6 33.1 I then increased the ...read more.

Conclusion

Also given more time I would have repeated any set of readings that after evaluation appeared to be anomalous and a poor fit. Despite the anomalous readings at 38oC, I consider my results were good enough to show clearly how rate of reaction of catalase changes with temperature, the more detailed investigation between 35 and 40oC also showed clearly that the optimum temperature for enzymes to work in is 37oC. I now know how temperature affects the rate of catalase activity. That the rate of reaction is speeded up as the temperature increases until its optimum at 37oC and then it rapidly drops again as fast as it increased, resulting in a bell shaped graph. However, there are several other factors that affect the rate of reaction, such as varying the concentration of catalase. To do this I would set up the apparatus like in the diagram I drew earlier in my coursework. I would need to ensure that the temperature stayed constant at 30 degrees, to ensure a fair test. First of all, take the 2% concentration of catalase. Test the pH of the solution using universal indicator. Then write down these two variables into a table, to ensure that the two variables are the same throughout the experiments. Once you have ensured that these two variables are right then add 0.2cm� of catalase into the side arm boiling tube with the 1cm� syringe. Then seal the side arm boiling tube with a bung. Through the hole in the syringe-adapted bung inject 5cm� of hydrogen peroxide (10vols) with the 5cm�, into the side arm boiling tube, and then start the stop clock as soon as the hydrogen peroxide has been dropped in. Record how much oxygen is collected in the gas tube cylinder every 10 seconds for the next 60 seconds into your table of results. Repeat this method 3 times for each concentration, 2%, 4%, 6%, 8% and 10%, of catalase and a control with 0% catalase, distilled water. ...read more.

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This is a well written and very detailed report.
1. The running commentary that runs throughout the report should be removed
2. The sources of information should be referenced
3. The analysis should quote data from the investigation to back up the patterns
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Marked by teacher Luke Smithen 17/09/2013

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