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Enzyme Coursework. Investigation to find the effect of substrate concentration on the rate of an enzyme controlled reaction

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Introduction

Investigation to find the effect of substrate concentration on the rate of an enzyme controlled reaction Design Aspect 1: Defining the problem and selecting variables Investigation title: is the rate of an enzyme controlled reaction affected by substrate concentration? Background information Enzymes are often referred to as "biological catalysts", since they increase the rate of reactions in living organisms. Enzymes are also substrate specific, which means that only a specific substrate can fit into its active site (which is where the catalysing effect occurs) and as such, there are different enzymes which deal with different reactions (for example, protease breaks down proteins into amino acids) - this is the basis for the 'lock and key' theory. The stages of an enzyme controlled reaction are: 1) Enzyme + substrate The enzyme and substrate are in solution together 2) Enzyme substrate complex A substrate has moved into the active site 3) Enzyme product complex The reaction has taken place, but the products haven't been released from the active site 4) Enzyme + product The enzyme and product are now in solution together (after the product was released from the active site) ...read more.

Middle

* the volume of the solutions 10cm� of hydrogen peroxide will be measured out by using a measuring cylinder for each test. * the temperature of the solutions The experiment will take place in an air conditioned laboratory, so it can be expected that the temperature will not vary enough over the course of the experiment to have a significant effect. * the pH of the solutions 1ml of pH7 buffer will be added to the solution. Aspect 3: Developing a method for the collection of sufficient data Apparatus * Hydrogen peroxide 1.00mol/dm-3 (150cm�) * Distilled water (75cm�) * Syringe (10cm�) * 15 test tubes * Stopwatch (seconds) * Pieces of paper * Hole punch * 3 petri dishes * 5cm� catalase enzyme * Safety glasses * pH7 buffer * Tweezers Method Preparing the hydrogen peroxide solutions Using the table below, prepare the various concentrations of hydrogen peroxide: Volume of distilled water (cm� ) Volume of 1mol/dm-3 hydrogen peroxide (cm� ) Concentration of hydrogen peroxide solution (mol/dm-3) 8.00 2.00 0.20 6.00 4.00 0.40 4.00 6.00 0.60 2.00 8.00 0.80 0.00 10.00 1.00 Label 5 rows of 3 test tubes with the different concentrations (0.20mol/dm-3 to 1.00mol/dm-3) ...read more.

Conclusion

As a result of this, the concentration of the enzyme present on the pieces of paper is uncertain (being soaked for a longer time will allow the piece of paper to absorb more catalase, which would speed up the reaction as there would be more of the enzymes). This does make the investigation less reliable, but the effect would have probably been only slight; however, to improve on this, the length of time that each piece of paper is soaked should be timed and kept the same. * Timing - although only a minor issues, human reflexes add a small margin of error in the times of each result, since the timing had to start as the pieces of paper touched the substrate and as soon as they touch the surface again. A computerised system could used in place of a human, but this would be costly and impractical to setup. * The concentrations of hydrogen peroxide didn't show the plateauing effect that was predicted - to improve on this, a greater range of concentrations could be used (for example 0.5M to 2M) which would clearly demonstrate the effect and completely prove the hypothesis. Steven Burnett IB Yr1 IB Biology Coursework 03/01/2011 ...read more.

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Response to the question

This Biology IA is outstanding in content and presentation, combining very accurate background information, easy-to-follow procedures listed out, relevant data presented in a coherent manner and insightful discussion and evaluation as well. The background information is more than needed and ...

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Response to the question

This Biology IA is outstanding in content and presentation, combining very accurate background information, easy-to-follow procedures listed out, relevant data presented in a coherent manner and insightful discussion and evaluation as well. The background information is more than needed and highlights just what is relevant instead of beating around the minor, irrelevant details. The IA mentions the investigating title but needs to reassert this by including the “aims and objectives” of the IA. The hypothesis needs more improvement as it is rather inaccurate and blur in focus, simply mentioning that there is an “effect” but without describing this effect or justifying why the effect will be as such. The writer identifies the correct independent and dependent variables while lists out a range of control variables as well. The writer also elaborates on these variables, how the concentration of peroxide solutions are varied, how the time taken is measured, how the various control variables might affect the experiment if they were different and so how they are maintained at a constant level as well. Coupled with very simple procedures, the IA also presents data very neatly and coherently. In the conclusion, the writer follows up on the data collected to conclude, justifying each conclusion with data. The evaluation section provides realistic ways to modify the experiment to improve it, and these modifications can actually enhance the experiment by a large margin, so the IA definitely answers the question overall.

Level of analysis

The IA definitely exceeds expectations in several aspects of analysis but also needs more improvement in other aspects. For example, the hypothesis needs more improvement as it is rather inaccurate and blur in focus, simply mentioning that there is an “effect” but without describing this effect or justifying why the effect will be as such. However, the variables section is very well done and can score well among markers as the writer elaborates on each variable instead of just listing them. The materials and apparatus section actually not just lists equipment used but also mentions other details such as quality, quantity, concentration and other details where relevant. Instead of listing the steps, the writer actually splits the IA into different sections and then lists the procedures under these sections. This enhances the organization of the IA. All tables show data with correct number of decimal values, the correct units, proper headings so the IA scores on data presentation as well, but to improve the uncertainties of instruments can be indicated as well to justify the decimal values of data. The evaluation section is excellent in that it lists of shortcoming of a specific procedure, explains how this might affect data, recommends other ways to improve and justifies how this might not affect data negatively. But, the quantity of evaluation could be increased as well.

Quality of writing

The whole IA has an excellent presentation. There are very few grammar or spelling errors but even these are not glaring errors. The use of technical terms is adequate and the IA explains the biology behind the whole IA. The IA defines technical terms where needed as well.


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