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Investigation into the effect of temperature on the activity of the enzyme urease.

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Investigation into the effect of temperature on the activity of the enzyme urease Urea + Urease ? Ammonium Carbonate The aim of this experiment is to investigate the affect of different temperatures on the rate of activity of the enzyme urease. I will achieve this by heating 5 solutions to different temperatures. They will be heated in a water bath and left for approximately 40 minutes. After this time, acid will be added to neutralize the solution and the activity of the enzyme will be measured via the volume of acid added. My predication is that as I increase the temperature of the solutions, the speed in which the reaction takes place, and amount of products produced will increase. However, I predict that at a high temperature the enzymes will denature and activity will cease. This is because of the following reasons. Firstly, at a high temperature, molecules are given more kinetic energy. ...read more.


Also, at around 60�C, the yeast ceased to be active, suggesting that denaturing of the enzymes occurred. Equipment Six test tubes, measuring cylinder, water baths, glass rod, mortar and pestle, 250ml beaker, stopwatch Method Preparing the urease solution 1. Crush one tablet of urease into a fine powder using the mortar and pestle 2. Add the powder to 3cm3 of distilled water in a test tube 3. Stir with a glass rod, and allow any insoluble substances to settle and then pour mixture off into clean test tube Heating the mixtures 1. Mix 1cm3 of urease solution with 10cm3 of 1% urea solution and pour into a test tube 2. Place the solution into a water bath at 20�C Measuring the activity 1. Add 2 or three drops of screened methyl orange indicator to the solution 2. Add 0.05 mol dm3 sulphuric acid by using a burette 3. Continually 'swirl' the solution 4. ...read more.


This however may need to be altered if tests at 60�C show some activity. Risk assessment Urea - Toxic Water spillage from baths could cause surfaces to be slippery - Wipe down wet surfaces Sulphuric Acid - Corrosive / Irritant Results Table My results will be obtained and recorded in a table similar to the one below. Temperature measured in '�C' and volume of sulphuric acid in 'cm3. Temperature (�C) Volume of sulphuric acid (cm3) 20�C 30�C 40�C 50�C 60�C Analysis of results Results would be analysed and then plotted on a line graph to compare the effects of the different concentrations. I will be looking for particular trends or similar curves on the graph to try to prove my prediction that as temperature increases so does rate of activity and to prove my theory of the 'cut off' temperatures. My main focus will be the temperature at which the activity at its slowest and quickest. High amounts of sulphuric acid will be interpreted as high activity, as more amounts of ammonium carbonate will be produced. Low amounts of acid will be the opposite of this. James Caullay 1 ...read more.

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Here's what a teacher thought of this essay

**Plan only. This is a very minimal plan which would be awarded little credit under current marking guidelines.
To improve
It does not inspire confidence in a plan when the first vital formula is incorrect. The candidate must check these carefully before submission.
There is some discussion of the background biological theory to this investigation but there is a lack of suitably selected references to assist in the planning and execution of the investigation. These should be beyond those most readily to hand textbooks and should be used effectively to provide some context for the investigation. The references should be cited appropriately.

A pilot experiment was carried out. The methodology for this as well as the results should be included as in some mark schemes this is expected and only the lower tier of marks is awarded if evidence of this is not included.

There needs to be more discussion on the key variables in the experiment. This is a key part of experimental planning. This can often best be achieved by constructing a table with the name of the variable in the first column, how it is to be controlled in the second column and the effect on the experiment if tit is not controlled well in the third column.
The method lacks some key information such as the strength and source of the urease.
The risk assessment would be considered unsatisfactory under some the newest marking guidelines since it lacks a lot of key information.
The headings for the results table need all units to be present and it would be expected that a candidate would plan for some replicates and a numerical or statistical method of analyzing the results.

Marked by teacher Stevie Fleming 22/08/2013

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