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AS Biology Coursework:Investigating the effect of temperature on the rate of reaction of the essence rennet

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AS Biology Coursework 2002: Investigating the effect of temperature on the rate of reaction of the essence rennet Plan Rennet contains enzymes called chymosin, which have the property of clotting, or curding milk. Chymosins' coagulate the protein casein found in milk, forming solid curds. 0They firstly break down specific bonds in a glycopeptides found on the surface of soluble calcium caseinate that contain casein, leaving relatively insoluble calcium paracaseinate (unstable, denuded casein particles). These particles in the presence of calcium (2-) ions coagulate to form a continuous curd. This property of coagulating milk makes rennet a biological enzyme that is used industrially in the production of cheese, yogurt, and other diary products. There are many forms of rennet, derived from different sources using different methods. In this investigation I will be using calf rennet, this has been derived from the inner lining of the fourth stomach of a calf. Other forms include, Maxiren (100% pure chymosine, made using rDNA technology) and rennilase (a fungal protease). Chymosin, known also as rennin, is a proteolytic enzyme (made up of protein), which is most stable between pH 5.5 and 6.0 hence it is ...read more.


increase in temperature the substrate can not bind with the enzyme slowly decreasing the rate at which the enzyme catalyses the reaction (rate at which the milk is coagulated). Once the higher temperatures are used this causes denaturation which is irreversible as it is the destruction of the tertiary structure of the enzyme. The destruction of the tertiary structure leads to the change of shape of the enzyme, resulting in the inactivity of the active sites. I hypothesis the optimum temperature will be between 39C and 41C which I have estimated researching though average enzyme optimum efficiency. Method Key Variables: * For all individual experiments, the temperature will be kept constant at the temperature been tested Controlled Variables: * Calf rennet concentration will be the same for all experiments * Milk type (whole milk, semi-skimmed) will be kept the same for all experiments * PH of milk will be same for all experiments (buffer solution will be used if pH is compromised) * Repeat each experiment at least three times Equipment: Water bath Ice 2 Pipette Test tube rack Calf rennet Whole milk 2 Thermometer Scale (electronic) ...read more.


After 4 minutes I will stop the stop watch and remove the milk (liquid-solid) and place on a muslin cloth, where I will drain away requiring liquid in the substance. Once there is only clotted milk left I will weigh the remains and record it. I will attempt the experiments at least three times to achieve a fair set of results within the time given. Equipment layout: Risk Assessment: * Calf rennet (chymosin enzymes) Are in standardized solution form. Enzymes are biologically active proteins so should be handled with care. May also irate the skin, eyes or mucous membrane - Avoid direct contact - Avoid inhalation - Clean up spillages immediately - DO NOT ALLOW TO DRY AND GENERATE DUST- after spillage Pilot test: In order to determine a suitable range of temperatures I could use I carried out a pilot test of the experiment. Results of pilot tests: Using 1cm Mass of maslin cloth BEFORE Temperature Mass of maslin cloth AFTER Mass of remains 0.98g 21C 1.56g 0.58g 0.99g 30C 2.83g 1.84g 1.01g 36C 5.37g 4.36g 0.92g 40C 4.21g 3.29g 1.02g 65C 1.38g 0.36g The two rows highlighted in red is the range that holds the enzymes optimum temperature. ...read more.

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