Enzyme Coursework. Investigation to find the effect of substrate concentration on the rate of an enzyme controlled reaction
Steven Burnett IB Yr1 IB Biology Coursework 03/01/2011
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:
- Enzyme + substrate
The enzyme and substrate are in solution together
- Enzyme substrate complex
A substrate has moved into the active site
- Enzyme product complex
The reaction has taken place, but the products haven't been released from the active site
- Enzyme + product
The enzyme and product are now in solution together (after the product was released from the active site)
The rate of an enzyme controlled reaction are mainly affected by: temperature, substrate concentration, enzyme concentration and pH. By increasing the substrate concentration, there is a higher chance of a substrate colliding with an enzyme and subsequently reacting (as there is simply more substrate moving around in the solution). Increasing the substrate concentration further will cause the rate of reaction to plateau when all of the enzymes' active sites are constantly in use – at which point the enzyme concentration can be considered a limiting factor.
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Peer Reviews
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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.
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.
Response to 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.
