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Investigation to see what effect the changing the concentration of calcium ions has on the rate of coagulation of milk by Rennin.

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Aim : Investigation to see what effect the changing the concentration of calcium ions has on the rate of coagulation of milk by Rennin. Theory Most milk proteins are caesins, which have four major forms: alpha-s1, alpha-s2, beta and kappa caesins. Alpha and beta caesins, when left on their own would precipitate in the presence of calcium. However, when associated with unperceivable kappa caesins, also present in milk, they form micelles which remain dissolved. (ref1) Rennin digests kappa casein, preventing it from aggregating the alpha and beta caesins into soluble micelles, effectively causing them to precipitate out naturally.(causing coagulation) And this precipitation requires calcium ions. Apparatus Rennin solution (50-100ml) Milk 2ml per 20cm� of milk. Sodium citrate solution, 2cm� (per test tube) 1.0 mol dcm� Calcium chloride solution Hot water bath set at 37�C 5 Test tubes 5 Pipettes 1 test tube rack Stop watch, to measure the time taken for the flecks or curd to appear. Safety goggles, to protect eyes from harmful chemicals. Syringes Slides, to dip into beaker/test tube. Introduction The problem that I am faced with is to get a sample of milk and try changing the concentrations of the calcium ions that are present in it. ...read more.


PH level; Enzymes are specific in their optimal pH. Calcium chloride is likely to be a weak acid because of the chlorine molecule, in which case it can have an affect on the enzyme. Rennin is accustomed to working in extremely acidic conditions and to tamper with that may damage the enzymes active site temporarily or permanently resulting in it not working, so I shall have to maintain pH, as close to being acidic as possible. During the conduction of this experiment I shall have to try and keep these factors the same. Prediction I predict that the higher the concentration of the calcium ions is the quicker the rate of coagulation of milk. This will happen because the more calcium ions there are, the higher the production of casein protein precipitation taking place at a time. Method The first step in this experiment is to add around 20cm� milk to the test tubes using a syringe to each of the five test tubes. I shall also have 5 different concentrations of sodium citrate solution to remove either all or some of the calcium ions that are present in the milk. ...read more.


I shall work out the rate of coagulation by doing. 1 / Time taken. Calcium Chloride Concentration(cm�) Time taken (s) 0.1 0.05 0.025 0.0125 0.0625 30 60 90 120 This I what my table of results will look like, with time taken for coagulation on the side and the concentrations of calcium chloride on the side. Precision and Reliability In order to get the most accurate of results I shall have to perform the experiment with the highest precision and reliability. For precision my measured values of calcium chloride and rennin solutions should be as close as possible to their actual values. The equipment that I will use for maximum precision are measuring cylinders, pipettes and rulers that measure to the nearest millimeter. For reliability I shall repeat the experiment that I have conducted at least 6 times and use the average of the results. Safety As I will constantly be in contact with irritant chemicals, I shall have to handle them with the utmost caution and also remember to wash my hands thoroughly after direct contact. I shall also be wearing safety goggles as rennin is a protein digesting enzyme, any contact with the eye can be extremely dangerous. Sources http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/Bio%20101/Bio%20101%20Laboratory/Enzymes/Enzymes.htm. (ref1) http://en.wikipedia.org/wiki/Rennet (ref2) ?? ?? ?? ?? Asad Shahid. 4195 51529 ...read more.

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