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Enzyme Investigation

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Biology Coursework Introduction I have to determine and choose one factor that will affect the rate of an enzyme and then investigate it. In this case the enzyme will be urease and the substrate will be urea. The following factors affect the rate that an enzyme works at: The temperature: Prediction - Reason - At higher temperatures usually there is an increase in enzyme activity. This is because as the temperature rises, the movement of enzyme molecules and substrate molecules increases. This increase in speed allows the substrate and enzyme to join and create the product quicker. If the temperature rises to high however, the enzyme activity declines rapidly as the heat denatures the enzyme. Below is an illustration of how the temperature can speed up the enzyme activity. Biology Coursework The pH: Enzymes are affected by changes in pH. The point where the enzyme is most active is known as the optimum pH. Extremely high or low pH values generally result in complete loss of activity for most enzymes. Prediction: Reason - I have predicted the optimum pH of Urease is 7, as urine is mainly made up of water (which has a pH7). Biology Coursework Substrate Concentration: Prediction: Reason - At very low substrate concentration, collisions between enzyme and substrate molecules are infrequent and reactions proceed slowly. ...read more.


I will use room temperature. I will also use 2cm3 of ethonic acid as it is just used to standardize a pH (starting point). Biology Coursework Method Biology Coursework Method Firstly prepare water bath to room temperature and note using a thermometer. Using a pipette put 5cm3 of Ethanoic acid into a test tube to form a starting point. Then put in 1cm3 of Universal Indicator using the pipette. The solution will turn into a red colour (acidic). Then place 5cm3 of Urea into the test tube. Then add 5cm3 of Urease and begin timing. The solution will go from red, to yellow and finally to green. Now stop timing. Repeat process 3 times and workout the average total. I should now change the quantity of Urease and start again. Extra Urea + water carbon dioxide + ammonia CO (NH2)2 + H2O CO2 + 2NH3 To test for the carbon dioxide I will use moist universal indicator paper and see if it turns orange. Obtaining Evidence Changes I made to my original plan - The only change I made to my original plan was to do an extra repeat (I got 3 readings for each experiment). This was because I had more time then I had initially anticipated and therefore made my results more accurate. ...read more.


What further work can be done? - This experiment can be taken further by using data-loggers that would provide much more accurate results. Each reading could be taken every 30 seconds. Also a different machine could have been used to measure the exact amount of urease in each experiment. More substrate concentrations also could have been used to prove the whole experiment was correct. More readings could have been taken to provide a more accurate average. Also a permanent constant temperature would result in better accuracy. Final Conclusion - In any chemical reaction, altering the concentration of reactants changes the rate at which the reaction takes place. Those reactions catalyzed by enzymes are no exception. If the amount of enzyme present is increased, the reaction speeds up proportionally. THIS IS TRUE AS LONG AS THERE IS PLENTY OF SUBSTRATE TO ACT UPON. This idea is best explained in a biology advanced studies book called 'Biochemistry' by Martin Carr and Bob Cordell. 'It it just like using a bus (i.e. the enzyme) to take a 1000 fans (i.e. the substrate molecules) to a football match (i.e. arrival = product). One bus will only do the job slowly, 2 buses will do the job twice as quickly, 3 will achieve three times the rate and so on. However, if there are only 20 fans to start with increasing the number of buses won't have great affect. Navad Khanzada 1 ...read more.

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Here's what a teacher thought of this essay

3 star(s)

*** An experiment that has produced usable data, but that is missing key sections that are needed to gain the highest credit.
To improve
The missing relevant biological background theory sections need to be included. Suitably selected and cited references should be included to help inform the planning. A quantitative prediction should be included and this should be explained using biological knowledge. The key reaction involved in this experiment should be explained fully as it is this mechanism that is being used to determine the rate of reaction.
There is not enough consideration given to the key variables in the experiment. There should be a table or section detailing the way in which variables are controlled, manipulated or taken into account. The results of all trial or pilot experiments should always be included in an experimental report.
A thorough risk assessment should be included.
The apparatus appears to have been used competently but the table headings are lacking key details such as concentration or Molarity of the solutions used. The candidate said that means would be included in an analyzing evidence section but this was not included.
Analysing and Evaluating
This section appears incomplete. There needs to be a conclusion stated that comments on the trends and patterns in the data explained using relevant biological principles. The limitations of the results, and the conclusions based on them should be recognized and evaluated. The evaluation and suggestions for modifications would benefit from a more extensive analysis and some comments need more scientific detail. For example stating that a 'machine' could measure urease concentrations lacks the explanation needed for A level work.

Marked by teacher Stevie Fleming 22/08/2013

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