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To find the effect of different concentration of calcium ions on the rate of coagulation of milk.

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Aim: To find the effect of different concentration of calcium ions on the rate of coagulation of milk. Background Research: protein molecules can take different types of structures. It's made up of several hundreds of amino acids joined together by peptide bonds. There are four different structures of protein molecules: 1. Primary structures: this is where a chain of amino acids are bonded by peptide bonds to form a polypeptide chain. 2. Secondary structures: there are two of these kind; * Alpha helix - the amino acids are bonded with other amino acids in the same polypeptide chains via hydrogen bonds between the -CO and -NH groups. A coiled structure of amino acids form. * Beta pleated - this is where the arrangement is much straighter than the previous type, although hydrogen bonds exist between the amino acid. 3. Tertiary structures: here, the secondary structure of a protein is further bonded into a more complex structure. This is due to several types of bonds that occur between the polypeptide chains. ...read more.


Risk Assessment: Sodium citrate is irritant when exposed to the skin. CaCl2 is also irritant to skin and eyes. However lower concentration will not pose any real threat although precautionary measures must be taken. Therefore, goggles and lab coats must be worn. Apparatus: Rennin solution 1ml syringe Milk 5ml syringe Sodium citrate 10ml syringe Testubes 50cm� beakers 1.0 mol dm of calcium chloride 50cm� measuring cylinder Distilled water Microscope Microscope slides Plastic Pipette Stop clock Method of Dilution: As only 1.0 mole dm-3 of CaCl2 is provided, I need to dilute it down to several concentrations. However, from preliminary testing, I found that 1.0 mol dm-3 is far too strong for the reaction as it forms flecks of curd instantly. Therefore I have decided to have my highest concentration as 0.5 moles dm-3. In order to dilute, I will have a total of 20cm� solutions of calcium chloride and water. To get different concentrations, I will change the ratio of CaCl2 to water. ...read more.


This varies from batch to batch. Therefore, I will have to assume that all calcium ions are removed. Then, 3. Using a 1ml syringe, add 1cm� of Rennin into each beakers containing milk. 4. For each of the beaker, add different concentrations of CaCl2 respectively using a 50cm� measuring cylinder and start recording the time. 5. As soon as the different concentrations of CaCl2 is added, dip a microscope slide in to the solution, remove it and observe it under a microscope to look for the appearance of flecks of curd. I will record the time it takes for flecks of curd to appear. Diagram: I will repeat the above experiment at least three times in order to get reliable information. Results Table: Beaker Vol. of Milk (cm�) Vol. of diluted CaCl2 (cm�) Conc. of CaCl2 (mol dm-3) Coagulation time(s) 1 10 20 0.50 2 10 20 0.25 3 10 20 0.125 4 10 20 0.10 5 10 20 0.0625 6 10 20 0. ...read more.

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