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Find out what effect different temperatures have on the enzyme, rennin, in milk.

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How Temperature Affects the Activity of Rennin in Milk Aim: To find out what effect different temperatures have on the enzyme, rennin, in milk. Introduction An enzyme is a biological catalyst. It speeds up a reaction by lowering the activation energy required to start the reaction. It speeds up a reaction, but remains unchanged unless certain limiting factors are introduced. It is composed of polymers of amino acids. An enzyme has an optimum pH and temperature. When an enzyme is at its optimum conditions, the rate of reaction is the fastest. In their globular structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, or the location on the enzyme where the substrate binds and the reaction takes place. An enzyme has an active site, which has a unique shape into which only a substrate of the exact same unique shape can fit. When this substrate fits into the active site, it forms an enzyme-substrate complex. This means that an enzyme is specific. The bonds that hold enzymes together are quite weak and so are easily broken by conditions that are very different when compared with their optimum conditions. When these bonds are broken the enzyme, along with the active site, is deformed, thus deactivating the enzyme. This is known as a denatured enzyme. The primary structure is the sequence of amino acids that make up a polypeptide chain. 20 different amino acids are found in proteins. The exact order of the amino acids in a specific protein is the primary sequence for that protein. Protein secondary structure refers to regular, repeated patterns of folding of the protein backbone. The two most common folding patterns are the alpha helix and the beta sheet. In this experiment, the enzyme rennin will be used. Rennin is a coagulating enzyme occurring in the gastric juice of the calf, forming the active principal of rennet and able to curdle milk. ...read more.


* The temperature of the milk in each test tube should then be measured. It should approximately be at room temperature in which case the milk should be heated, as it is not at the correct temperature (30?C). * This can be done by putting quite hot water into a large beaker. A thermometer should then be placed into one of the test tubes containing the milk and the all three test tubes should be placed in the beaker which acts as a water bath. The thermometer should be placed in each of the test tubes alternately to ensure that the correct temperature is being attained for each test tube. * When the temperature reaches 30?C, the test tubes should be taken out of the water bath. If any of the test tubes exceed the required temperature, a thermometer should be paced in that particular one and it should then be left to cool down until it is at the precise temperature. * 1ml of rennin should be measured out using another syringe. * Once they are all at the required temperature, 1ml of the rennin should be added to the test tube. At the same time, the stopwatch should be started and a bung should be placed on the test tube. * This should then be repeated ten seconds later with the second test tube, i.e. when the initial test tube has had ten seconds to coagulate. Once again, this should be repeated with the third test tube of milk at 30?C, but this time the rennin has to be added twenty seconds after the rennin has been added to the first test tube. * The test rubes should be placed in the boiling tube in the clamp every 15s. Once it can be seen that the milk is thickening substantially but not quite fully coagulated, the test should be carried out every 10s. ...read more.


This method was not extremely reliable as many things could have potentially gone wrong. Firstly, the problem of heat loss or gain could have considerably changed the results by lowering or raising the temperature by a few degrees. Some kind of insulation should have been placed around the test tube constantly. This could have been in the form of cotton wool or bubble wrap. Also the rennin may have cooled down or heated up whilst it was in the beaker owing to the room temperature and the temperature of the rennin at the start (without the milk was never measured). This may have also affected the actual test tubes which contained both the rennin and the milk. Again, to improve this, some form of insulation should be used and the temperature of the rennin should be taken before it is added to the milk. One thermometer had to be used when there were three test tubes in the water bath, so this may have made some of the temperatures of the repeats slightly different. One thermometer per test tube should have been used or perhaps some kind of computer software should have been used. I would also vary the types of milk used in this experiment. For example full fat, semi skimmed, and skimmed milk could be used and these results can be compared. Also milk from other animals such as goat and buffalo milk can be used. Perhaps even milk such as soy can be tested. The ratio of substrate to enzyme can also be varied as well as the concentration of each substance. To provide extensional evidence for this experiment, different levels of pH should be used, such as the optimum pH that is about 2. This could be achieved by adding acidic or alkaline compounds to the milk. However, at certain levels of ph the rate of reaction (the acidic pHs) would be so fast that it would be too fast to time. Nevertheless, this could be done using computerised equipment. This could also be done in conjunction with varying the temperature. ...read more.

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