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How does varying the concentration Rennin affect the coagulation time of Milk

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Biology Assessed Practical 2002 How does varying the concentration Rennin affect the coagulation 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. 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 > The concentration of Rennin > The concentration of Milk > The volume of Rennin > The ...read more.


(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.) * Place 1 thermometer in the 5% Rennin test tube and the other thermometer into a test tube of milk. * When the Rennin and Milk have reached 40 degrees centigrade. Measure 1ml of Rennin into a measuring cylinder. * Pour the 1ml of Rennin into one test tube of Milk. * Start the stopwatch. * 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) * Place the test tube back in the test tube rack. * Repeat the above steps using bungs 2 and 3, still with the 5% Rennin solution. (Multiple Results) * Repeat the above steps again but this time using the 4%, 3%, 2% and 1% solutions of Rennin. * Record results in this table... Concentration of Rennin Volume of Rennin (mls) Volume of Water (mls) Results Set 1 (seconds) ...read more.


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. Laura Wetherill 11FJWa 5th February 2002 ...read more.

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