Enzyme Practical

Design your own experiment: Effect of pH on enzymatic activity

Background Information:
Trypsin is a protease which conducts hydrolysis forming peptides. It is an enzyme which is secreted by the pancreas into the small intestine and works best in an alkaline environment. Egg white is used in this practical as it is found to contain the protein/ enzyme trypsin. pH is the measure of the amount of H+ ions in a solution, these ions affect the shape of the enzyme.
Hypothesis:
That as pH increases, the rate of enzymatic activity increases until the optimum pH is reached.
Aim:
To investigate the effects of different pH levels on reactions catalysed by the enzyme trypsin.
Risk Assessment:
RISK
ASSESS
CONTROL
Trypsin solution, NaOH solution and HCl Solution
The solutions are irritant to the skin and can be lethal is consumed. It can also be harmful if contacted with eyes.
Wear safety goggles during use of solutions, if splashed onto skin, immediately rinse with cold water.
Cuts from glass
Cuts to skin when breakage occurs
Immediately inform teacher and follow instructions to clear away glass
Burns from heat
Burns to skin from hot water, hot milk or Bunsen flame

Immediately hold under cold water and inform teacher

Variables:
Independent
pH of solution
Dependent
Optimum pH level ie, whether protein disappears (digestion)
Controlled
Pepsin, egg white.
Experimental Control
Test tube with water

Method:
1. Collect 4 test tubes and label them from A to D.
2. Add about 20mm of egg white into each test tube.
3. Add 3 drops into test tubes A, B and C.
4. Add 10 mL water into test tube A and D as a test of neutral pH.
5. Add 10 mL Hydrochloric acid into test tube B as an acidic pH test.
6. Add 10 mL Sodium Hydroxide into test tube C resulting as a basic pH test.
7. Heat the test tubes in a water bath until they all reach approximately 37oC.
8. Remove the test tubes from the heat after 10 minutes and record any observations in a table.

Repeat:
Repeat the experiment 10 times with the aim of achieving consistent results, this will increase the reliability of the experiment.
Discussion:
1. A control experiment must be performed. Why is it performed and what did yours show?
A control experiment must be performed so you can observe the effects of your test and how variables can alter results. Mine showed that as pH levels increase, the enzymatic activity increases, this is shown by the control which had no effect as opposed to the one with an acidic pH which gave the desired results which was that digestion had occurred as a result of an increased pH.
2. What variables did you control and how did you do it?
I controlled the pepsin by using it in all different pH level tests except for the control. This was done to see whether the absence of the enzyme had an effect on the substrate.
3. If you were to repeat your experiment how and why would you do things differently?
I would have repeated the experiment however, I would have had a control for each of the different pH levels to observe the effects of the enzyme.