Laboratory #5 - ENZYMES

Enzymes are biological molecules that catalyze many different chemical reactions. With few exceptions, all enzymes are proteins and each enzyme is specific to a certain chemical reaction. Enzymes must maintain a specific three dimensional structure in order to function properly. If an enzyme's structure is altered (by heat or harsh chemicals) it may not function at all. This breakdown (denaturation) of an enzyme'sstructure may be fatal (your body cannot withstand a fever over 108 degrees for very long). After completing this lab, you should be familiar with the following terms: The enzyme used in this lab exercise is amylase, which is commonly found in saliva and germinating seeds. It catalyzes the breakdown of starch. When amylase reacts with starch, it cuts off the disaccharide maltose (two glucose molecules linked together). As the reaction progresses, less starch will be present and more sugar (maltose) will be present. In lab, the activity of amylase was observed by using iodine. Remember, iodine reacts with starch to form a dark brown/purple color. As amylase breaks down starch, less and less starch will be present and the color of the solution (if iodine is added) will become lighter and lighter. The color change was observed using spot-plates as illustrated on the diagram below.




Amylase activity was observed under four different treatments:
  1. effect of temperature
  2. effect of pH
  3. effect of substrate concentration
  4. effect of enzyme concentration



1. EFFECT OF TEMPERATURE:

The following graph shows data recorded from the "effect of temperature" portion of the lab experiment. Based on these results, at what temperature does amylase react the fastest? What do you think would happen if the temperature were raised above boiling (100 C)?




2. EFFECT OF pH:

The following graph shows data recorded from the "effect of pH" portion of the lab experiment. Based on these results, what is the optimal pH for amylase? Is this optimal pH considered acidic, basic/alkaline, or neutral? Why does the activity decrease when the pH is too low or too high?




3. EFFECT OF SUBSTRATE CONCENTRATION:

The following graph shows data recorded from the "effect of substrate concentration" portion of the lab experiment. Remember, the substrate is the compound that is acted upon by an enzyme. In this exercise, starch is the substrate. Based on these results, why does it take more time to completely hydrolyze the starch as the starch concentration increases?




4. EFFECT OF ENZYME CONCENTRATION:

The following graph shows data recorded from the "effect of enzyme concentration" portion of the lab experiment. In this exercise, amylase is the substrate. Based on these results, why does it take less time to hydrolyze the starch when there is more and more enzyme present?



This concludes the review for Lab 5 - Enzymes.




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