Investigating+the+Effect+of+Temperature+and+pH+on+Enzyme+Action

__Part A

Part B__

**Test Tube** || **Contents** || **Iodine Test At the beginning** || **Iodine test after 10 minutes** || **Conclusion** || W || 2cm^3 of starch solution + 2cm^3 of HCl + 2cm^3 of amylase || Iodine turned blue-black in colour || Iodine turned blue-black in colour || If the pH level is lower than neutral (pH 7), enzyme action will not occur. || X || 2cm^3 of starch solution + 2cm^3 of distilled water + 2cm^3 of amylase || No visible change in colour of iodine || No visible change in colour of iodine || If the pH level is at 7, enzyme action will occur. || Y || 2cm^3 of starch solution + 2cm^3 of NH4OH + 2cm^3 of amylase || Iodine turned blue-black in colour || Iodine turned blue-black in colour || If the pH level is higher than neutral (pH 7), enzyme action will not occur. || Z || 2cm^3 of starch solution + 2cm^3 of distilled water || Iodine turned blue-black in colour || Iodine turned blue-black in colour || Amylase is needed to break down the starch into glucose. ||

1. Which tube shows that starch digestion has occurred? Give your reasons. Test tube X. Iodine will only turn colour when starch is present. When starch is digested, it turns into glucose. Iodine will not change colour when glucose is present, and there was no visible change of colour in the iodine in test tube X, hence test tube X shows that starch digestion has occured.

2. Which of the test-tubes contained mixtures that gave a blue-black colour? Test-tube W, Y and Z.

3. Why did the mixtures in tubes stated in (2) remain blue-black? After ten minutes, the pH level was still not neutral, and so enzyme action could not occur.

4. What conclusion(s), based on the observations in this experiment, can be made about the effect of pH on enzyme action? If the pH level is not neutral, enzyme action cannot occur.

5. How does temperature and pH affect enzyme action?