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The effect of enzyme concentration on enzyme activity.

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Core practical - the effect of enzymes The effect of enzyme concentration on enzyme activity Introduction This experiment relates significantly to the pancreatic duct because in cystic fibrosis suffers this can become blocked by mucus. The pancreas has an exocrine function by producing digestive enzymes. These go through the pancreatic duct to the small intestine where food is digested, however this release of enzymes is prevented or restricted as a result of the duct being blocked. This means that less enzyme concentration is released so digestion is not as good. In this experiment I will be adding distilled water to the enzyme to make protease to make different enzyme concentrations. Then adding these separate concentrations to a milk powder solution containing the substrate protein casein and timing how long it takes each solution to clear. Hypothesis The substrate solution will clear quicker with a higher enzyme concentration. Enzymes are a type of globular protein which acts as a biological catalyst. They have poly-peptide chains folded into a compact spherical shape which keeps its structure by bonding between amino acids. The structure makes a three dimentional shape which is vital in catalysing reactions within cells and forming the enzyme-substrate complexes. A depression on the three dimentional shaped surface of the molecule is the active site. ...read more.


The different concentrations can be achieved by mixing different quantities of 1cm3 of distilled water with the acidified enzyme protease. The 5 different concentrations of enzyme solution will include 1cm32cm33cm34cm 3 and5cm3. * Now 5 testubes need to be filled with exactly the same volume of 5cm3 of milk powder substrate solution containing the protein casein. * Pipette each 5mc3 enzyme concentration solution into separate substrate solutions. * Start the stop clock immediately and record the time taken up to the point when the milk powder protein solutions clear. * Repeat the procedures 3 times so that consistent results can be obtained for a suitable average result. Independent variable The independent variable is the concentration of acidified protease enzyme used. The different concentrations used will be: Protease cm3 % Distilled water cm3 % 1 20 4 80 2 40 3 60 3 60 2 40 4 80 1 20 5 100 0 0 These different concentration levels will be accurately changed measuring xcm3 of enzyme and xcm3 of distilled water to the appropriate ratio of volume each and mixing them together. Each enzyme solution contains an exact volume of 5cm3. Dependent variable The dependent variable involved is the time taken for all the casein to be broken down clearing the milk powder solution. The time will be measured immediately after the protease has been completely added to the milk using a stop clock measuring to 1/100ths. ...read more.


As time increased less protease was being used as continuously less casein molecules need breaking down, therefore gradually decreasing the rate of reaction. However the 20% represents an anomalous result because the time taken was not in proportion to the other results. This could have been caused by over diluting the protease making it less reactive or by adding too much of the substrate increasing the amount of reactions to take place. Conclusion: In conclusion to this experiment I am very pleased as it was carried out well and accurately apart from one anomalous result. Many improvements can be made to the experiment to make it more reliable and accurate. Specialised equipment would be an appropriate option to make all measurement more accurate, eg, to measure the volume to 0.01cm3 instead of 0.1cm3. I can calculate the %error of the volume measurement to see how accurate it was: %error = 0.1cm3 X 100 = 2% 5cm3 This shows that the volume of the solutions was measured very accurately, however 10X more precise equipment would lead to just a 0.2% error which is extremely good. Also repeating the experiment many more times, taking 10 trials instead of 3 will illustrate results more accurately and analysis would be more critical. Finally to improve the experiment I would use a much wider range of % concentrations adding to the reliability of the experiment results. Daniel Abdelmassih Page 1 of 5 ...read more.

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This is fair attempt at writing up an investigation into the effect of enzyme activity on reaction rate using the action of protease on milk protein. The writer has a reasonable grasp of the theory behind the practical. He/she addresses most of the key areas which make up good scientific practice. However, the report would have benefited greatly from the following improvements: [1] A detailed introduction to the biochemistry of enzyme concentration and reaction rates; [2] More careful use of the terms 'accurate', 'reliable' and 'precise'. [3] A more thorough treatment of controlled variables where specific levels of each variable were stated; [4] A detailed risk assessment in standard format (risk/risk management); [5] A more detailed analysis of results discussed in the light of work carried out by other biologists. Many of these points are common areas of weakness in GCSE and A'Level reports and this particular essay is therefore a useful learning tool.

Marked by teacher Ross Robertson 10/04/2013

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