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Enzyme concentration and enzyme activity. Trypsin

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Enzyme concentrations and enzyme activity Purpose: To investigate how enzyme concentration can affect the rate of reaction, in this case the breakdown of protein by protease enzyme. The protein substrate in this reaction will be trypsin milk protein (casein). Background: Trypsin is an endopeptidase, protease enzyme that is made in the pancreas and used to digest proteins so that the body can absorb them into the blood. The pancreatic duct in people who have cyctic fibrosis frequently becomes blocked, reducing or preventing the release of pancreatic enzyme ino the small intestine. Enzymes are biological catalysts made up from protein that changes the speed of chemical reactions without themselves being changed at the end of the reaction. Enzyme action occurs at the surface of the enzyme called the "active site" which has a shape complementary to the substrate, when the enzyme and substrate collide, the substrate locks into the enzyme's active site. The active site alters its shape holding to the substrate tightly, an enzyme-substrate complex is formed in which the substrate undergoes the reaction. ...read more.


Mix thoroughly so the enzyme spread out evenly, and immediately start the stop clock. 3. Record the time taken for the protein solution to clear, when the protein has been digested. 4. Repeat the procedure with range of 5 different enzyme concentrations (20% 40% 60% 80% 100%) by mixing the protease with water. Concentration of protease % Volume of protease cm3 Volume of water added cm3 100 5 0 80 4 1 60 3 2 40 2 3 20 1 4 Safety: All enzymes are potential allergens so handle with care to minimize skin contact and inhalation. Results: Concentration of enzyme % Time taken for solution to clear (min) Time taken for solution to clear (sec) 20 8.14 494 40 6.32 392 60 4.45 285 80 3.54 234 100 2.23 143 Analysis: The results I have obtained shows that a decrease in concentration of enzymes results in an increase in the time taken for the solution to clear. In other words, as the concentration of protease decreases, the amount of active sites where the reaction takes place also decrease, therefore causing ...read more.


I will prevent this from affecting the results by not stirring or shaking the mixtures in any way at all and will add the solutions in an order, eg. Enzyme followed by substrate. Other factors in which error could have occurred are inaccurate measurements of the solutions, when to start timing - here, starting the clock must be done immediately after mixing the solutions, I might have started the clock at different times during each experiment due to not being totally in control of the experiment, and temperature of the surroundings - temperature affect the rate of reaction. If the temperature of the surroundings changes, this can cause a temperature change in the solution, causing unreliable results. So to extent this experiment I could investigate the effect of temperature on the rate of reaction or enzyme activity, or any other variables such as the concentration of the substrate, finding the point which increasing concentration doesn't affect the rate of reaction as all the enzymes- active sites are used up. ...read more.

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*** This a basic practical write up that has obtained a set of usable data but is missing the depth and detail that would be required for an A2 coursework report.
To improve
Research and rationale
Whilst some background knowledge is included it is expected that some research is carried out and carefully selected for inclusion to help inform the plan.
The variables could be considered more carefully , such as the use of a thermostatically controlled waterbath and the use of a buffer. The written method should include full details such as the source and strength of the stock solutions. Whilst the range of concentrations was adequate, it should be expected that replicates or class data are included.
Some data has been recorded but the headings of the tables could be more informative. It should have been possible to get replicate data in the time available.
Analysis and evaluation
The graph was only partially visible so it is difficult to comment but the discussion of the results does refer to biological knowledge. It would be helpful to have seen a calculation of rate and the comparison of rates at different temperature intervals. if background research had been carried out then the actual results could have been compared to those found in the literature. The evaluation could be improved by detailing a proposed method for using the colorimeter to measure transmission.

Marked by teacher Stevie Fleming 22/08/2013

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