Varying Concentration of Rennin and Its Effect on the Goagulation Time of Milk

Varying Concentration of Rennin and Its Effect on the Goagulation Time of Milk
Scientific Knowledge Enzymes Enzymes are large molecules, which are protein in nature. They are biological catalysts that speed up chemical reactions in the body. They operate by a ?lock and key? method. The Enzyme has a certain ?lock? (active site) that only a specified substrates ?key? will fit into. Enzyme action Rennin A proteolytic enzyme that speeds up the coagulation of milk. It is usually found in the tissues of a calves fourth stomach. Its purpose is to coagulate the milk in young animals so that the proteins have time to be extracted, rather than flowing straight through the digestive system. This particular enzyme catalyses the conversion of the protein in milk (caseinogen) into paracasein. This forms a thick curd in the stomach meaning the milk can be exposed to Rennin for a greater period of time. Milk Milk is an almost complete food. It consists of proteins (mainly casein), salts, fat and milk sugar, or lactose. It also contains vitamins A, C, D, certain B vitamins, and small amounts of others. Factors That May Affect The Reaction Ø The concentration of Rennin Ø The concentration of Milk Ø The volume of Rennin Ø The volume of Milk Ø The temperature of the reaction Ø Agitation The factor I have chosen to explore is the concentration of Rennin because I believe that varying the temperature of the reaction is very hard to control and therefore may be inaccurate and agitation is a very simple investigation. I have a prediction for the investigation concerning the concentration of Rennin, another reason I chose this factor. Prediction I predict that as the concentration of rennin increases the rate of reaction will increase. I believe this to be true because if there are an increased number of enzymes, more milk particles will be broken up at any one time into the substance, which coagulates the milk, resulting in an increased rate of reaction. I also predict that eventually all the milk will be coagulated by a certain number of enzymes in a certain time. If after this point the concentration is still increased, it will make no reaction and the experiment will be in excess of Rennin. I predict the graph to show an increase in rate of reaction corresponding to an increase in the concentration of rennin. Eventually though the graph will straighten out with a constant and maximum rate of reaction for the controlled amount of milk. Equipment ü 75mls of Milk ü 25mls of 5% Rennin ü 10mls of Water ü Test tubes ü 1 Measuring Cylinder ü 3 Stopwatches ü 3 Bungs ü 1 China Graph Pencil ü 1 Water Bath (40 Degrees Centigrade) ü 1 Test tube holder ü 2 pipettes ü 2 Thermometers Diagram Description of the Experiment When Milk and Rennin are added together, the milk, after a short period of time changes state to a more viscous fluid and eventually solid. The reactants do not change colour and there is no other visible effect apart from coagulation. This experiment is preformed in a heated water bath. Method Preparing the concentrations of Rennin Â? Use a pipette to measure the volumes of Rennin and Water (shown below in the table) into 5 separate test tubes. Â? Label each test tube with its corresponding Percentage of Rennin with a china graph pencil. Â? Place the test tubes in the test tube holder. Place the test tube holder in the water bath. Concentration of Rennin Volume of Rennin (mls) Volume of Water (mls) 5% 5 0 4% 4 1 3% 3 2 2% 2 3 1% 1 4 Reacting Milk with Rennin Â? Take 3 clean test tubes and fill each with 5mls of milk. Â? Place these three test tubes in the water bath. Â? Label 3 stopwatches with a china graph pencil: 1, 2 and 3. Â? Label 3 bungs with a china graph pencil: 1,2 and 3. (This means that the stopwatches will not be muddled up and it is possible to take more than one result at one time. This saves a lot of time is very efficient.) Â? Place 1 thermometer in the 5% Rennin test tube and the other thermometer into a test tube of milk. Â? When the Rennin and Milk have reached 40 degrees centigrade. Measure 1ml of Rennin into a measuring cylinder. Â? Pour the 1ml of Rennin into one test tube of Milk. Â? Start the stopwatch. Â? Place bung number 1 into the top of the test tube and rotate the test tube 180 degrees 6 times. (i.e. Agitating the test tube by placing it upside down and upright 3 times each way) Â? Place the test tube back in the test tube rack. Â? Repeat the above steps using bungs 2 and 3, still with the 5% Rennin solution. (Multiple Results) Â? Repeat the above steps again but this time using the 4%, 3%, 2% and 1% solutions of Rennin. Â? Record results in this tableâ?? Concentration of Rennin Volume of Rennin (mls) Volume of Water (mls) Results Set 1 (seconds) Results Set 2 (seconds) Results Set 3 (seconds) Results Average (seconds) 1% 1 4 2% 2 3 3% 3 2 4% 4 1 5% 5 0 Fair Testing (Variables and Controls) Variable Ø Concentration of Rennin Controls Ø Concentration of Milk Ø Temperature of both substances Ø Agitation Ø Equipment This was a fair test because there was only one variable. If there were more than one variable it would be impossible to see how much the concentration of Rennin affected the rate of coagulation. The temperature was kept constant because I know that the more heat energy a substance is exposed to the more kinetic energy its particles have. This means they collide more frequently at a higher speed resulting in a faster rate of reaction. It is important to make sure all equipment is clean so that the Milk or Rennin do not get contaminated because this will effect the results of the investigation making it inaccurate. Agitation speeds up the rate of reaction. If this agitation however is kept at a constant i.e. each test tube is agitated 6 times in the same way, this will not affect the end result of the experiment. If one test tube was agitated 4 times, another 12 and another 8 then this would definitely affect the rate of reaction and cause unfair testing. Results Concentration of Rennin Volume of Rennin (mls) Volume of Water (mls) Results Set 1 (seconds) Results Set 2 (seconds) Results Set 3 (seconds) Results Average (seconds) 1% 1 4 244 230 238 237 2% 2 3 176 174 172 174 3% 3 2 154 154 140 149 4% 4 1 113 110 112 112 5% 5 0 105 99 89 98 Graph of averages to show how the concentration of Rennin affects the coagulation time of milk. Anomalous Results The graph shows a line of best fit that travels through 4 points on the graph. An anomalous result was recorded for the 3% rennin test. This could be due to many factors such as: v Human error when stopping stopwatches v Contaminated equipment or reactants v Human error when creating the concentration of Rennin v Human error when measuring the volume of Rennin v Human error when measuring the volume of Milk v Human error while agitating the reactants It is impossible to isolate only one cause. Conclusion The results show that as the concentration of Rennin is increased by a constant factor then the difference in the time of the reaction decreasing by a decreasing increment each time (within experimental error) E.g. From 1% (237 seconds) to 2% (174 seconds) Factor = 2 Difference in reaction time = 63 seconds From 1.5% (201 seconds) to 3% (138 seconds) Factor = 2 Difference in reaction time = 63 seconds From 2% (174 seconds) to 4% (112 seconds) Factor = 2 Difference in reaction time = 62 seconds From 2.5% (154 seconds) to 5% (98 seconds) Factor = 2 Difference in reaction time = 56 seconds From 1% (237 seconds) to 1.25% (218 seconds) Factor = 1.25 Difference in reaction time = 19 seconds From 4% (112 seconds) to 5% (98 seconds) Factor = 1.25 Difference in reaction time = 14 seconds The difference in the reaction/coagulation time of the milk is constantly decreasing, this suggests that it will eventually reach zero. At this point there will be no further decrease in the time it takes to coagulate 5 mls of milk with increasing concentrations of added Rennin. No matter how much rennin is added after the difference in reaction time has reached zero the reaction time will not change. Evaluation I believe this experiment was a success because the prediction has been proved correct and only one anomalous result was gained. This is backed up by various books and websites such as the neab Chemistry Science Revision Guide of 1998 onwards that states: "Increased concentration means an increased number of particles resulting in an increased number of collisions and an increased rate of reaction." If I were to do the experiment again I would take more results and widen the range of concentrations. I could also expand this investigation by exploring other factors like how pH affects the coagulation time of 5mls of milk.

Varying Concentration of Rennin and Its Effect on the Goagulation Time of Milk 8.4 of 10 on the basis of 1315 Review.