Effect+of+temperature+and+pH+on+enzyme+action

Table 1 - Results of iodine test
 * Test tube || A1 || B1 || C1 || D1 ||
 * Iodine test || Blue-black || Brown || Blue-black || Blue-black ||

1) Which tube shows that starch digestion has occured? Give your reasons. B1 shows that starch digestion has occured. In the beginning, B1 contained starch. However, after the experiment, the iodine turned brown in the iodine test. This shows that there was no starch present at the end of the experiment, therefore starch digestion had occured in B1.

2) Which of the test-tubes contained mixtures that gave a blue-black colour? A1, C1 and D1.

3) Why did the mixtures in tubes stated in (2) remain blue-black? The amylase was not able to react with the starch in A1 and C1 at such extreme temperatures. (one freezing, one boiling). There was no amylase present in D1, so the mixtures in these 3 test tubes were able to retain their starch since enzyme reaction did not take place.

4) What purpose does the tube D1 serve? It acts as a control for B1.

5) Using your knowledge of the structure of starch, describe the test you would use to detect the presence of the substance produced as a result of the reaction in test tube stated in (1) above?

6) What conclusion, based on the observations in this experiment, can be made about the effect of temperature on enzyme action. Enzyme action cannot take place at extreme temperatures. (i.e. freezing and boiling points of water)

Table 2 - Results of starch digestion using amylase in different conditions
 * Test tube || Contents || Iodine test before 10 minutes || Iodine test after 10 minutes ||
 * W || 2cm^3 starch solution, 2cm^3 HCl, 2cm^3 amylase || Blue-black || Blue-black ||
 * X || 2cm^3 starch solution, 2cm^3 distilled water, 2cm^3 amylase || Blue-black || Blue-black ||
 * Y || 2cm^3 starch solution, 2cm^3 NH4OH, 2cm^3 amylase || Blue-black || Brown ||
 * Z || 2cm^3 starch solution, 4cm^3 distilled water || Blue-black || Blue-black ||

1) Which tube shows that starch digestion has occured? Give your reasons. Tube Y shows that starch digestion has occured. In the beginning, Y contained starch. However, after the experiment, the iodine turned brown in the iodine test. This shows that there was no starch present at the end of the experiment, therefore starch digestion had occured in Y.

2) Which of the test-tubes contained mixture that gave a blue-black colour? Tubes W,X and Z.

3) Why did the mixtures in tubes stated in (2) remain blue-black? The pH of the mixtures in W and X were not suitable for enzyme reaction to take place, while Z did not contain amylase needed for the reaction, therefore the starch was remained in the solutions.

4) What conclusion(s), based on the observations in this experiment, can be made about the effect of pH on enzyme action? Enzyme action takes place best when the pH is alkaline.

5) How does temperature and pH affect enzyme action? Enzyme action cannot take place at extreme temperatures, and take place when the pH is above 7 (alkaline).