• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

OCR AS Biology Planning Exercise 2008

Extracts from this document...


OCR Biology Planning Exercise 2008 The effect of the Concentration of Calcium ions on the Coagulation of Milk Aim/Problem The aim of this project is to investigate the correlation between the amount of calcium ions in an amount of milk and amount of time it takes for the milk to coagulate. Hypothesis I think that the more calcium ions there are in the milk, the faster the milk will coagulate. Also, I think that milk with no calcium ions in will not coagulate at all. The purpose of milk coagulating is so that when milk is drunk by infant mammals it can coagulate in the stomach so that it is there long enough to be digested. Rennin is a protein-digesting enzyme that curdles milk.[1] Rennin affects milk by breaking peptide bonds. Once these peptide bonds between hydrophobic and hydrophilic groups in the milk are broken, the hydrophobic group would unite together and would form a 3D network to trap the aqueous phase of the milk. The resultant product is calcium phosphocaseinate. [2] Therefore, I think that when there are fewer calcium ions in the milk, the reaction that produces calcium phosphocaseinate (which appears as coagulation) ...read more.


* You will be using glass beakers which could be smashed, so you should be careful not to cut yourself on shards of glass if this happens. Apparatus * Rennin solution * Milk * Sodium citrate * 1.0 mol dm-3 calcium chloride solution * Microscope (and lamp, if necessary) * 5cm3 syringe (for measuring out milk, calcium chloride and water) * 1cm3 syringe (for measuring out sodium citrate and rennin solution) * Boiling tube * Slide and cover slip * Pipette * Electronic stopwatch Method 1. Ensure that your work area is clean and safe 2. Measure out 10cm3 of milk with a syringe and put it into a boiling tube 3. Add 1cm3 of sodium citrate solution to get rid of any calcium ions already present in the milk 4. Next, measure out the correct amounts of water and calcium chloride using the table below to make a solution using different 5cm3 syringes. Concentration Amount of Water (cm3) Amount of Calcium chloride (cm3) 0M 5 0 0.2M 4 1 0.4M 3 2 0.6M 2 3 0.8M 1 4 1M 0 5 5. Add this solution to the milk 6. ...read more.


stopwatch) as these are more accurate. Although, the stopwatch could be a problem as it is impossible to add the rennin and start the stopwatch at the same time which could cause a slight delay and make the results out by a second or two. The fact that human judgment is used to tell when the coagulation starts could be a problem as people have different ideas about when the coagulation has started. A device such as a colorimeter could be used instead as this would give an accurate measurement that everyone could keep to and no room for human error at this stage would be left. I think that the experiment is definitely valid as it shows exactly what has been asked (a comparison between concentration of calcium ions and time of coagulation) and the data can be shown in many ways (e.g. a graph or a table). To make the results reliable you could repeat the experiment more than twice. Overall however, I think my experiment is reliable enough and quite fair. There are variables beyond our control, of course (such as air temperature or pressure) which could affect the rate of coagulation, and the experiment would have to be carried out in a sealed environment such as a laboratory to rectify this. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Molecules & Cells essays

  1. Affect of concentration of calcium ions on the coagulation of milk

    The dilution factor and amount of calcium chloride required is calculated by the following equations: Dilution factor = Original concentration New Concentration Volume of CaCl2 required = Dilute solution volume Dilution factor For example: Dilution factor = Original concentration = 1.0 mol dm-3 = 2.5 New Concentration 0.4 mol dm-3

  2. An Investigation On The Effects Of Calcium Ions On The Coagulation Of Milk

    Preliminary Results Samples A B C D E F Time for Coagulation (seconds) N/A 73 42 22 14 9 As shown on the graph, I have coded the time using the function R.O.R = (1/time) X 100, this gives me a set of data which can be interpreted as the rate of reaction.

  1. Rennin investigationMy experiment is also to see how long it takes for milk and ...

    When the temperature was above 55 �C the enzyme changed shape and denatured. My prediction matched my results because as I said in my prediction that the reaction will be faster and will work best at body temperature. I also said that the enzymes will denature if the temperatures are

  2. A Level Biology revision notes

    of reaction, provided other conditions are constant o Straight line * Substrate conc. o Proportional to rate of reaction until there are more substrates than enzymes present o Rate of reaction increases * Substrate binds to active site, but more enzymes are available * Rate increases if more substrate is added o Eventually, curve becomes constant (no increased rate)

  1. Investigation to find out what effect changing the concentration of calcium ions has on ...

    Repeat the entire experiment a further 2 times to ensure the results are consistent and reliable. Finally calculate the mean time for each concentration. IX. Calculate the rate of coagulation for each concentration, by using: Rate of Reaction = Analysis of results Precision, Reliability and Validity The main source

  2. To find out what factors affect the rate of reaction between rennin and milk.

    within the enzyme, and therefore change the shape of the active site until the substrate is unable to fit into it - ie it is denatured. 11. Concentration of Enzyme How will the concentration of the rennin affect the rate of reaction?

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

    Amino acids in a polypeptide chain have an effect on each other even if they are not directly next to each other. The chains bend upon themselves and so distorting the shape of the molecule. The thermal energy breaks the hydrogen bonds holding the secondary structure of the enzyme together,

  2. What Effect Does The Temperature Of Water Used Have On The Rate Of Coagulation ...

    It is the shape of the active site that must be specific (due to the enzymes tertiary structure) so that the substrate fits into the active site and the reaction can occur. The specific shape of the active site is due to the bonds between the R groups.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work