1_temp_pH_effect_on_enzyme_action


 * __ Biology Lab Report __**
 * Investigating the effect of temperature and pH on enzyme action **
 * Topic: Biomolecules **
 * Done by: Jessie Lim, 3/11 (9) **

To find out how difference in temperature and pH level affect enzyme action in starch by testing for the presence of starch on various set-ups
 * // Aim //**
 * // Predictions //**

We measured the presence/absence of starch using the iodine test on solutions (containing amalyse) in different test tubes after 10 minutes in a water bath of different temperatures to see if enzyme action has taken place. Also, in part B, the pH level of the solution was the variable. // Difficulties faced // When preparing the water baths, we had to do it quickly so that all the test tubes could be placed in the various water baths at the same time. Also, it was difficult to obtain the water bath of 37 degrees C as the right amount of hot water and tap water. // Precautions taken // We ensured that the water level of the water baths was higher than the water level of the test tubes. We also measured everything as accurately as possible, using the measuring cylinder to measure the liquids at the bottom of the meniscus, as well as measuring temperature by viewing the thermometer at eye-level. We recorded the time correctly for both parts of the experiment. // Assumptions made // We assumed that the reactions would start occurring immediately after the solutions were mixed. Observations and Results //**
 * // Method //**
 * Part A **
 * Test tube || Contents || Temperature/ ° C  || Iodine test at 10 min. || Conclusion (after water bath) ||
 * A1 || Starch || 0 || Turns blue-black || Starch present ||
 * B1 || Starch || 37 || Turns blue-black || Starch present ||
 * C1 || Starch || 100 || Turns blue-black || Starch present ||
 * D1 || Starch || 37 || Turns blue-black || Starch present ||
 * A2 || Amylase || 0 || Remains brown || Starch absent ||
 * B2 || Amylase || 37 || Remains brown || Starch absent ||
 * C2 || Amylase || 100 || Remains brown || Starch absent ||
 * D2 || Distilled Water || 37 || Remains brown || Starch absent ||

All at 37 ° C  From what we understand of the experiment, the variable in Part A is temperature while the variable in Part B is pH. The solutions in the test tubes undergo a process called starch digestion, where the starch (substrate) is broken down by the amalyse (enzyme), into another product, in this case, sugar. Analysis of results and Questions //**  1. Which tube shows that starch digestion has occurred? Give your reasons. The tubes A2, B2, C2 and D2 show that starch digestion has occurred, as the iodine test indicated the absence of starch in the mixtures in these test tubes.  2. Which of the test tubes contained mixtures that gave a blue-black colour? Test tubes A1, B1, C1 and D1.  3. Why did the mixtures turn blue-black? It indicates the presence of starch in the mixture, because the substrate starch has not been broken down by any enzyme and is thus still present.  4. What purpose did test tube D1 serve? It acted as a control set-up for us to confirm and compare our results.  5. Using your knowledge on the structure of starch, describe the test you would use to detect the presence of substance produced as a result of the reaction stated in 1. Since starch forms sugar when broken down, we can use the Benedict’s test for reducing sugar as a test to detect the presence of the product of enzyme action.  6. What conclusions, based on the observations in this experiment, can be made about the effect of temperature on enzyme action. The temperature of the mixture has little/no effect on enzyme action.  7. Which tube shows that starch digestion has occurred? Give your reasons. The tubes W, X, Y and Z show that starch digestion has occurred.  8. Which of the test tubes contained mixtures that gave a blue-black colour? None.  9. Why did the mixtures turn blue-black? -  10. What conclusions, based on the observations in this experiment, can be made about the effect of pH on enzyme action.
 * Part B **
 * Test tube || Contents || Iodine test (0 min) || Iodine test (10 min) || Conclusion ||
 * W || Starch, HCl, amylase || Remains brown || Remains brown || Starch absent ||
 * X || Starch, water, amylase || Remains brown || Remains brown || Starch absent ||
 * Y || Starch, NH4OH, amylase || Remains brown || Remains brown || Starch absent ||
 * Z || Starch, Distilled water || Remains brown || Remains brown || Starch absent ||

 11. How does temperature and pH affect enzyme action?