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To investigate how enzyme concentration can affect the rate of reaction, in this case the breakdown of milk protein by trypsin, a protease enzyme.

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Biology - Activity 2.10 Enzyme concentrations and enzyme activity Aim To investigate how enzyme concentration can affect the rate of reaction, in this case the breakdown of milk protein by trypsin, a protease enzyme. Hypothesis 1. The higher the concentration of trypsin, the higher the rate of breakdown of milk protein. Reason: with higher concentration of enzyme, there are more active sites available for the substrate molecules to bind with. When there are more enzymes, the collision between enzymes and substrates becomes more frequent, increasing the chance of forming enzyme-substrate complex. 2. Increase in rate of reaction is directly proportional to increase in trypsin concentration. Reason: enzyme concentration exerts a direct effect on the rate of reaction. Apparatus o Milk o Trypsin o 3 Syringes o 5 test tubes o test tube rack o 5 stopwatches o Distilled water Procedure In this experiment, the rate of reaction is determined by the time taken for a given quantity of substrate to be used up: 1. ...read more.


4. Tap the bases of the test tubes to mix the solutions. 5. Measure the time needed for the milk to turn clear in each test tube. Variables Independent variable Dependant variable Controlled variable Concentration of trypsin Time Temperature Volume of milk Volume of trypsin-water solution Test tube A is a control. Explanation: Test tube A contains distilled water only. It ensures that the clearing of milk in other tubes is due to enzyme activity only and not any other factor. Risk and safety precautions Take care handling glassware. Results Test tube Vol of trypsin/cm3 Vol of distilled water/cm3 Time/s Trypsin concentration/% Reaction rate=1/T A 0 2.0 0 0 B 0.5 1.5 550 25 0.001818182 C 1.0 1.0 364 50 0.002747253 D 1.5 0.5 297 75 0.003367003 E 2.0 0 242 100 0.004132231 Two graphs are plotted. ...read more.


2. Increase in reaction rate is proportional to increase in trypsin concentration. Reason: increase in the number of trypsin molecules results in a proportional increase in the number of enzyme-substrate complexes and therefore a proportional increase in the rate of reaction. Limitations and error 1. This experiment does not measure the initial rates of reaction because the quantity of product formed in a fixed period of time from the breakdown of milk protein is not easily observable. Instead, average rates of reaction are measured by determining the time needed for all milk protein to react, i.e. for the reaction to complete. A graph of average rate of reaction against trypsin concentration does not show an accurate straight line. 2. Tapping and shaking the test tubes too vigorously added kinetic energy to the trypsin and milk proteins, making temperature, the controlled variable, not constant. Improvement Shake the test tubes slowly. ...read more.

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