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Rate of reaction

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Introduction

EXPERIMENT TO INVESTIGATE THE EFFECTS OF DIFFERENT PH MEASUREMENT ON THE ACTIVITY OF THE ENZYME CATALASE Aim: To investigate the effects of different PH measurements on the activities of the enzyme catalase. Hypothesis: As the measure of the pH is increased, the enzyme's activity will also increase. The enzymes optimum pH will be around 7-8 and after this Ph is reached, increase in the pH will decrease enzyme activity. Theory: Enzymes are protein molecules that can be defined as biological catalysts. A catalyst is a substance that initiates or accelerates a chemical reaction without itself being affected by the reaction. Enzymes lower the activation energy of a reaction, so that the rate of the reaction increases. The concentration of the hydrogen ions affects the ionic bonds. If the pH changes much from the enzyme's optimum, the chemical nature of the amino acids can change and this may result a change in the bonds and so the tertiary structure may break down. The active site of the enzyme will be disrupted and so the enzyme will be denatured. Enzyme and substrate concentration can also affect the rate of reaction. At low enzyme concentrations, there is great competition for the active sites and the rate of reaction is low. As the enzyme concentration increases, there are more active sites available and so more substrates can bind unto the active sites enabling the rate of reaction to proceed at a faster rate. Eventually, increasing the enzyme concentration beyond a certain pint has no effect because the substrate concentration becomes a limiting factor. This point is the optimal concentration. At a low substrate concentration there are many unoccupied active sites and this means that the rate of reaction is low. When more substrate molecules are added, more enzyme-substrate complexes can be formed as there are more active sites and the rate of reaction increases. Again, increasing the substrate concentration further passed the optimal point will only result a decrease reaction rate. ...read more.

Middle

o Time using a clock how far the liquid in the manometer travels in a space of 3 minutes. Measurements should be taken every one minute until the 3 minute time is reached. Variable Control Dependent - the rate of the reaction Independent - the concentration of the catalase * The pH is going to change as the aim of the experiment is to investigate how different pH affects the enzyme activity. * The enzyme quantity will be kept as close as possible to been constant. This is because if the enzyme quantity changes, the pH will not be the only variable affecting enzyme activity as enzyme concentration can also affect the rate of reaction * The temperature should be kept constant because it can also affect enzyme activity. * The same volume of pH concentrations to be used. This will ensure fair results. A syringe will be used to take the accurate measurements. Risk Assessment 1) Laboratory cloths should be properly worn during the cause of the experiment. 2) Goggles and gloves should be worn at all times to prevent solutions like the hydrogen peroxide from reaching the skin. Hydrogen peroxide is a toxic and so great care should be taken whilst it is been used. 3) To handle all apparatus (mainly scalpel) with care. This is because such equipments can easily inflict harm on an individual if not handled with the appropriate care due to its sharp edges. TABLE OF RESULTS First Trial Number of potato discs pH concentration Distance travelled/Time (min) 1 minute 2 minutes 3 minutes 10 4 2.5cm 4.2cm 5.5cm 10 5 4.1cm 6.0cm 7.0cm 10 6 4.0cm 6.3cm 8.7cm 10 7 6.7cm 9.5cm 10.4cm 10 8 6.4cm 9.1cm 10.2cm 10 9 6.3cm 9.2cm 10.0cm Second Trial Number of potato discs pH concentration Distance travelled/Time (min) 1 minute 2 minutes 3 minutes 10 4 3.0cm 4.3cm 5.3cm 10 5 4.0cm 5.9cm 7.5cm 10 6 4.3cm 6.4cm 8.6cm 10 7 6.5cm 9.4cm 11.2cm 10 8 5.8cm 8.9cm 10.5cm 10 9 6.2cm 8.7cm 11.0cm Average and Rate of reaction table pH Concentration Average distance travelled in 3mins. ...read more.

Conclusion

Evaluation - Improvements If I was to do the experiment again, I would take some further factors into consideration; a) I would use a wider range of concentration of enzyme to acquire a greater range of results to investigate and compare. b) I would use smaller test tubes because this could have an effect on the amount of collisions that occur and so the rate of reactions could possibly increase. The closer the particles are, the more chance of enzyme-substrate complexes been formed. c) I could use a gas syringe with a glass pipe as an alternative instead of the manometer, as some gas may have been lost through it. d) Possibly use more potatoes in grams because it could increase the amount of gas produced e) I would also use a more accurate concentration of catalase; example by using a solution. Evaluation - Protocol change The procedure could be improved although the results do give adequate conclusions. Improvements in the protocol would help remove certain errors and improve accuracy of the results. Using a method that doesn't require the manometer could result accurate readings been taken. This is because the manometer had some setbacks which included the liquid overflowing once the reaction was fast and over a long period of time. Also the liquid in the manometer sometimes had to restart its travel due to a limited space for it to travel. This occurred mainly in the reaction with the pH 7. A suggestion of such strategy would be to use equipments which didn't require the use of the manometer. Example of such strategy had been presented below: i) ii) Overall, I believe the experiment was a success and so I can conclude that the aim was achieved with the prediction been correct; if the amount of enzyme is kept constant and the pH is then gradually instead, the reaction rate will increase until the optimum working rate is achieved. ?? ?? ?? ?? Charles Badu-Boateng E1 Candidate Number: 0349 1 Biology Coursework ...read more.

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