Core practicals Flashcards
What is the PH and enzyme activity practical?
The Iodine test which tests for the presence of starch through the enzyme amylase. You use this test to show how effective amylase is in digesting starch at different pHs.
How does The iodine test show how effective amylase is at digesting starch?
Amylase is an enzyme made in the salivary glands in your mouth and in the pancreas. It catalyses the breakdown of starch into smaller sugar molecules. The iodine test identifies the presence of starch, but does not react with sugar. If there is still starch, amylase has not finished breaking it down and the solution will be black. If the solution is yellow, all the starch has been broken down. This reaction can be timed under different factor like PH to investigate the effect of such factors on the speed of the reaction.
Outline a method for the iodine test.
1) Drop one drop of iodine solution into each depression of the dimple tile.
2) Measure amylase into a test tube with a syringe.
3) Add 1 cm3 of your pH solution to the test tube. Record the pH of the solution.
4) Add the starch solution to the mixture and start the stopwatch and stir
4) After 20 seconds, take a small amount of the mixture in the pipette and place one drop of it on the first iodine drop on the tile.
5) If the iodine solution turns black, then there is still starch in the mixture and you should repeat step E (after 10 seconds). If it remains yellow, then all the starch is digested and you should record the time taken for this to happen.
6) If there is time, repeat the experiment using a solution with a different pH.
What is the control variable in the iodine test?
- temperature
- volume of iodine solution
- volume of amylase, starch, and ph solution
- time of each sample
- Concentration of starch/amylase
What is the independent variable in the iodine test?
The Ph
What is the dependent variable?
The time taken for the starch to be broken down
What improvements could be made to the iodine test to make it better?
- increased intermediate pHs tested around the optimum
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