Back
Home
1.10 identify data sources, plan, choose equipment or resources and perform a first-hand investigation to test the effect of:
identify data sources, plan, choose , equipment or resources and perform a first-hand investigation to test the effect of:
- increased temperature
- change in pH
- change in substrate concentration
on the activity of named enzyme(s)
- For this investigation, you need data that will assist you to determine appropriate ways in which each aspect may be researched. Enzymes that could be used include salivary amylase, trypsin and rennin.
Rennin is an enzyme found in the stomachs of young mammals that are still being fed on milk. The rennin ‘curdles’ or sets the protein in the milk separating it into curds (solids) and whey (liquid).
- Plan your investigation using the procedure provided below.
- When choosing resources, you should be able to buy rennin as a junket tablet from supermarkets.
Procedures to investigate the activity of an enzyme
A. To demonstrate the effect of increased temperature:
- Make a rennin solution by dissolving a junket tablet in distilled water.
- Add the same amount of rennin solution to a number of test tubes of milk, eg 7 test tubes.
- Place test tubes in different water baths at temperature ranges such as 0oC, 10oC, 20oC, 30oC, 40oC, 50oC and 60oC. Make sure each water bath is kept at the temperature it has been allocated.
- Time the interval between adding the rennin and curdling of the milk for each temperature.
- Note that the variables kept constant in each test tube are the junket solution, the pH of the solution, the type of milk and the quantity of milk in each test tube.
- Comment on which temperature is the most effective in curdling the milk. Could a different temperature be better?
B. To demonstrate the effect of change in pH:
- Make a rennin solution the same as was done in A and add pH solution to each with known concentrations of pH solutions from for example pH 3, pH 4, pH 5, pH 6, pH 7 and pH 8.
- Add the same amount of rennin solution with the varying pH to six test tubes of milk.
- Place in a water bath kept at a constant temperature of 37oC.
- Time the interval between adding the rennin and curdling of the milk in each test tube.
- Note that the variables kept constant in each test tube are the junket solution, the type of milk, the temperature of 37oC, and the quantity of milk in each test tube.
- Comment on which pH is the most effective in curdling the milk.
C. To demonstrate the effect of change in substrate concentration:
- Make different concentrations of the substrate by diluting the milk using different amounts of powdered milk to get different concentrations.
- Add the same amount of rennin solution to each test tube of milk.
- Place in a water bath kept at a constant temperature of 37oC.
- Time the interval between adding the rennin and curdling of the milk.
- Note that the variables kept constant in each test tube are the type of milk, the temperature of 37oC, and the quantity of milk in each test tube.
- Should smaller increments of milk concentrations have been used?
- Perform the investigation by using the procedures above and carrying them out, recognising where and when modifications are needed and analysing the effect of any adjustments that you make.