Enzymes and Proteins Biology Lab Report

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Exercise 7 – Enzymes (6/2019) 1 ENZYMES Student Learning Outcomes At the completion of this exercise you should: (1) Be able to describe how Benedict's test can be used to detect the presence of reducing sugars like Glucose and Fructose. (2) Be able to describe how enzymes, like Invertase, work on their substrates to produce products. (3) Be able to describe the general effect that temperature and pH have on the rate of an enzyme’s activity. (4) Be able to describe the question, hypothesis and results obtained in the temperature and pH enzyme experiments. (5) Be able to define pH and describe what a pH buffer is. (6) Be able to design an experiment to test the effect of iodine on the activity of the enzyme invertase. I. Preliminary Observations A. Introduction: General Information about Enzymes Enzymes are substances which make it possible for organisms to carry out the variety of metabolic activities necessary for life. Each of the numerous chemical reactions in a living system is mediated by an enzyme. For example, in the lumen of the mammalian digestive tract, especially the small intestine, large "food" particles are enzymatically broken down into molecules small enough to be absorbed into the blood stream and thus carried to all the cells of the body tissues. Also, within the individual cells, hundreds of different enzymes catalyze the breakdown and syntheses of organic molecules in a continuing process which makes possible cellular maintenance, growth and reproduction. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 2 Enzymes are just one of several categories of proteins. Each enzyme is a protein molecule that is different in some respect from that of any other kind of enzyme. This uniqueness of structure allows each type of enzyme to mediate only one specific chemical reaction, or at most a series of very similar reactions. Enzyme molecules are also known to be very sensitive to their environments. For example, exposure to high temperatures, chemicals such as strong acids and other factors often can denature an enzyme's structure, making it unable to carry out its function. An enzyme can therefore act only if it is structurally intact, and only within a limited range of environmental conditions. Enzymes act as biochemical catalysts. It is thought that their presence reduces the activation energy necessary to start a chemical reaction. The rate at which the chemical reaction proceeds is therefore accelerated, and the end products are formed more rapidly. The enzyme molecule itself remains unchanged during the reaction and does not become a part of the end products. Therefore, enzymes are reused, as the same enzyme molecule may perform the same function many times, each time converting a new substrate molecule into the same kind of product molecule. B. The Enzyme Invertase: A Representative Example for Today's Studies The enzyme invertase has been selected as a representative example for demonstrating the effects of some environmental factors on enzyme activity. (Enzyme names often have the suffix "-ase.") The invertase which we shall use in this experiment was produced by yeast, a singlecelled organism (actually a kind of fungus). In humans, a similar enzyme (called sucrase), produced by the pancreas, operates in the small intestine. The specific reaction that invertase catalyzes is the breakdown of the double sugar (disaccharide) sucrose into the two simple sugars (monosaccharides), glucose and fructose. It accomplishes this by rupturing the chemical bond that links the simple sugars in the sucrose. The reaction can occur only in the presence of water: one molecule of water is required to break apart the disaccharide and, by so doing, completes the structures of the monosaccharides. Breakdown of molecules with the addition of water is called hydrolysis. This same reaction occurs routinely in the human small intestine and allows the absorption into the bloodstream of carbohydrates as monosaccharides. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 3 Question 1. Any enzyme converts substances generally known as substrates into substances commonly called products. For the reaction shown above, name the substrates and products below. Then label them on the drawing above. a. substrate(s): b. product(s): Question 2. If a student mixes some sucrose and invertase solutions in a test tube and allows some time for reaction, what results would you predict? C. How to Tell If Invertase Has Done Its Job: Benedict's Test 1. Why Do We Need Benedict's Test? Of course, we cannot see the enzyme invertase in solution, as it is colorless. As you may already know, neither can we see the sugars sucrose, glucose or fructose when they are dissolved. However, we do wish to measure the rate at which invertase catalyzes the hydrolysis of sucrose into glucose and fructose. Clever ways to do this might include a chemical test to reveal the presence or absence of sucrose or a different test for the products of the reaction. Fortunately, biochemists have developed such a technique, called Benedict's test. This test uses a special solution of chemicals - called Benedict's reagent a clear, blue solution which gets its color from the dissolved copper compound, cupric hydroxide Cu(OH)2. 2. Interpretation of Benedict's Test When Benedict's reagent is heated, the solution will change color and develop a distinctive precipitate, if certain sugars known as reducing sugars have been added. It has already been established (through experiments) that all monosaccharides, but not all disaccharides, are reducing sugars. If only a small amount of reducing sugar is present, the Benedict's reagent will form a greenish precipitate which may or may not settle out in the bottom of the test tube. If larger amounts are present, one sees a more yellowish color with definite precipitation at the bottom of the test tube; with still larger amounts, an abundance of orange-red-brown precipitate will be apparent. On your tables of results, you may note the color and use symbols (-, +, ++, +++, etc.) to indicate the relative amount of reducing sugar revealed by the test. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 4 D. Observing the Benedict’s Test General Procedure: 1. Turn on your hotplate. 2. Place a small test tube rack in a beaker. Fill the beaker one-third to one-half full of tap water, and place it on your hot plate. Bring the water to a gentle boil. . 3. Throughout this experiment, keep all glassware scrupulously clean. Even trace amounts of enzyme carried over from one part of the experiment to another may distort the results. Use a test tube brush, and rinse well because soap can interfere with enzyme activity. 4. Obtain four clean test tubes, and label with a grease pencil. them 1-4 5. Add two ml (or 20 drops) of "test a test tube. (See Table 1 for each of solutions.) Be sure to read the dispenser labels to confirm how are dispensing with each pump solution" to the “test solution much you 2 ml 2 ml Benedict's reagent "test" solution 1. To each test tube containing the "test add two ml Benedict's reagent. solution," 7. Hold the sides of the test tube near its top, and then gently tap the side near the bottom. This will create a small vortex in which the contents are mixed. Swirl each test tube to mix the contents thoroughly. 8. Place the test tubes in your boiling water bath for three minutes, no longer. Exceeding this time limit can lead to false positive results 9. Carefully, remove the tubes from the bath, place them in your test tube rack and observe. (You may use your bare fingers after you test the tops of the test tubes for the temperature, or you may use test tube clamps if you know how to use them. The tubes shouldn’t get too hot to handle.) 1. If the solution forms layers, homogenize the solution by gently tapping the side of the tube near the bottom with the pad of your index finger. 11. Interpret the results for each tube (as described above in Interpretation of Benedict’s Test), and record the results in the Table 1. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 5 E. Using the Benedict's Test: How can it be used to detect for presence of monosaccharides (reducing sugars) like Glucose and Fructose? Watch this video: https://www.youtube.com/watch?v=rYZW0m_JZuQ&list=PL r27cjny01UsC4aQozbzjEFbadMg07c5b&i ndex=2&t=0s In order to use Benedict's test in later experiments, one must first observe the results when the test is performed on four solutions whose contents are known to us: 1% sucrose, 1% fructose, 1% glucose and deionized water. Following the directions given in part D (previous page), perform a Benedict's test on each of the four known test solutions listed in Table 1 (below) and record your results. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 6 Table 1: Benedict's Test on Known Solutions Test Tube Number Test Solution Benedict's Test Results: Color 1 1% sucrose 2 1% fructose 3 1% glucose 4 DI* water Benedict's Test Results: Precipitate (-, +, ++, +++, etc.) * deionized water (water which contains no ions) Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 7 Question 3. What was the purpose of testing deionized water? Question 4. A student arrives at the lab on Saturday. S/he wants to verify that the stock invertase solution left over from Friday's lab is still "good". The student mixes some 1% sucrose and some of the stock enzyme solution in a test tube and lets it stand in the test tube rack for one-half hour. Then the student performs a Benedict's test on the test tube contents. a. What is the correct interpretation of the Benedict's test if the result is a clear, blue solution? Is the enzyme active or not? b. What is the correct interpretation if Benedict's test shows a bright orange precipitate? Is the stock enzyme still "good"? II. Factors Affecting Enzyme Activity A. Experiment 1: Effect of Temperature on Invertase Activity We all know that living systems are extremely sensitive to environmental temperature. Upon reflection, it may seem likely to you that even the individual chemical reactions of living cells could possess such sensitivity. To investigate this possibility for enzyme-mediated reactions, we shall set up a controlled experiment to test the effects of a few selected temperatures on invertase activity. While it is possible for us to test the enzyme's response to a wide spectrum of temperatures. today we have selected just four for observation: 0o C (freezing point of water) 25° C (usual room temperature in our laboratory) 37° C (slightly higher than normal human body temperature--37°C) 100° C (boiling point of water) Question 5. Based on what you already know about living things, in what general range of temperature do you expect enzyme molecules to function best? We will have 4 “groups.” a. What is the dependent variable? b. What is the independent variable? c. State your answer as a hypothesis for this part of the exercise in an If…, and …, then … format. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 8 Procedure Watch this video https://www.youtube.com/watch?v=3NgEjCMXtfM&list=PL r27cjny01UsC4aQozbzjEFbadMg07c5b&index=3&t=0s When watching the video pay close attention to which temperature changes color first. You MUST keep track of which tube is which in the video. 1. Prepare enzyme tubes: a. Label four clean test tubes respectively as follows: "0°C enzyme" "25°C enzyme," "37°C enzyme" and "100°C enzyme." b. To each of the "enzyme" tubes, add 2.0 mL stock enzyme solution and 2.0 mL pH 4.4 buffer solution. c. Homogenize the solutions by tapping the bottom of your test tube as you did in the Benedict’s test. 2. Prepare substrate tubes: a. Obtain four more clean test tubes, and label as follows: "0°C substrate," "25°C substrate," "37°C substrate" and "100°C substrate." b. To each of the "substrate" tubes, add 2.0 mL 1% sucrose solution. 3. Place all eight test tubes in their marked temperature conditions as follows: a. Place both "0°C" tubes in the ice bath with ice slurry on the side bench near the sink. b. Place both "25°C" tubes in your test tube rack on your lab bench. c. Place both "37°C" tubes in the warm water bath near the sink. d. Place both "100°C" tubes in the boiling water bath on your bench. 3. Check the temperatures of the 0°C and 37°C baths to confirm their temperatures. If there are differences in the actual temperatures, write down the actual temperatures next to letters a-d in step 3 above. 4. Allow ten minutes for the contents of the tubes to reach the actual temperatures of their respective environments. 5. After the ten-minute equilibration period, mix the contents of the tubes as follows: Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 0°C substrate 9 0°C enzyme a. Pour the contents of each "substrate" tube into the ''enzyme" tube at the same temperature. b. Mix the solutions by tapping the test tube bottoms with the pad of your index finger. Then return each "enzyme" tube to its marked temperature environment. (The empty "substrate" tubes may now be washed for later use.) 6. At this point, allow ten minutes more for the enzyme-substrate reaction to proceed at the various temperatures. 7. Use Benedict's Test to assess invertase's performance. a. While you are waiting for completion of step 6 (above), thoroughly wash and number four more test tubes in preparation for performing Benedict's test. Remember to label the tubes. b. Add 2.0 mL Benedict's solution to each tube. c. Obtain four clean pipettes. d. After you have allowed 10 minutes for the enzyme--substrate reactions (as directed in part "6" above), gather the four reaction tubes from the 0°C, 25°C, 40°C and 100°C water baths and place them on the table next to your four labeled tubes containing Benedict's solution. Immediately proceed to the following steps. e. Using a clean pipette, transfer 20 drops of your enzyme-substrate reaction mixture from the tube labelled "0° C." to the tube containing 2 mL Benedict's solution, labelled "0° C." f. Using another clean Pipette each time, repeat step "e" for the "25° C", "37° C" .and "100° C" tubes. g. Now place the four Benedict's test tubes in your boiling water bath for exactly three minutes. Use a clamp to remove them to your test tube rack. h. Record your results in Table 2. Paying attention to which changed color first in the video. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 10 Table 2: Invertase Activity at Different Temperatures Test Tube Number Temperature of Test Solution Benedict's Test Results: Benedict's Test Color Precipitate Results: (-, +, ++, +++, etc.) 1 0oC 2 25 o C 3 37 o C 4 100 o C Question 6. At which temperature was invertase most active? Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 11 At which temperature was invertase least active? Describe how you arrived at your decision: Question 7. Recall Exercise 3: "Diffusion and Osmosis", where you observed the India ink dye. What happened to the molecular motion as you increased the light intensity (heat)? In that exercise, you learned the relationship between heat and molecular motion. a. State the relationship: b. Referring to Table 2, identify which of your results can be explained by this relationship. Explain your reasoning. c. Which part of your Table 2 data are not consistent with the relationship between heat and molecular motion? d. What do you know about enzymes (and proteins in general) which can account for your results at 100°C? (You may need to consult your textbook's discussion of protein molecules to answer this question.) This should include the following concepts: 1) Structure/function/denaturation 2) Bonds – types of bonds affected B. Experiment 2: Effect of pH on Invertase Activity The pH of a solution tells us its relative acidity or basicity. ("alkaline" is another word for "basic.") It is well known that most living things cannot survive pH extremes, and generally thrive in environments whose pH values are close to neutral. For example, the cells of your body are living in a fluid whose pH averages about 7.4. As added "protection" against pH extremes, body fluids contain solutes called buffers, whose chemical nature causes the fluid to resist changes in pH. Many cellular waste products are acidic and could decrease the body's pH if the buffers were not present. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 12 If living cells are sensitive to pH, perhaps enzyme-mediated reactions also possess such sensitivity. Today we shall observe the activity of the enzyme invertase in four buffered solutions* at the following pHs: pH 1.0 pH 4.4 pH 8.0 pH 12.0 *Note: the word “buffer” is used to describe pH solutions whose chemical nature causes the fluid to resist changes in pH. Question 8. List the pH's of the above buffered solutions in order from most acidic to most basic: (most acidic) (most basic) Question 9. What pH is called "neutral"? ______________ Question 10. What is the pH of pure water? ______________ Question 11. Based on what you already know about living things, in what general range of pH do you expect enzyme molecules to function best? We will have 4 “groups.” d. What is the dependent variable? e. What is the independent variable? f. State your answer as a hypothesis for this part of the exercise in an If…, and …, then … format. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 13 Procedure: Watch this video. https://www.youtube.com/watch?v=JYyCDE637Wc&list=PL r27cjny01UsC4aQozbzjEFbadMg07c5b&index=4&t=0s (Caution: pH 1.0 and 12.0 can burn skin or clothing. If spills occur--even a drop on skin or clothes--flush with plenty of water and call your instructor.) 1. Set up enzyme reactions in four selected pH buffer solutions: a. Label 4 clean test tubes respectively as follows: "pH 1.0", "pH 4.4", "pH" 8.0" and "pH 12.0." b. Add 2.0 mL stock enzyme solution to each tube. c. Add 4.0 ml of the proper pH buffer solution to each tube. Use the marked laboratory stock pH buffer solutions. d. Add 2.0 mL 1% sucrose solutions to each tube. e. Homogenize the solutions by tapping the bottom of your test tube as you did in the Benedict’s test. f. Allow 10 minutes for the enzyme-substrate reactions to proceed. 2. Use Benedict's test to assess invertase's performance. a. While you are waiting for completion of step 1e (above), wash and number four test tubes in preparation for performing Benedict's test. Remember to label the tubes (pH 1.0, pH 4.4, pH 8.0, pH 12.0). b. Add 2.0 ml Benedict's solution to each tube. c. Obtain four clean pipettes. d. After you have allowed 10 minutes for the enzyme substrate reactions, as directed in part 1e (above), immediately proceed with the following steps. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) e. Using a clean pipette, transfer 20 drops of your enzymesubstrate reaction mixture from the tube labeled "pH 1.0" to the tube containing 2 ml Benedict's solution, labeled "pH 1.0 14 20 drops 2 ml Benedict's "pH 1.0" "pH 1.0" f. Using another clean pipette each time, repeat step "e" (just above) for the "pH 4.4," "pH 8.0'' and "pH 12.0" tubes. g. Now place the four Benedict's test tubes in your boiling water bath for exactly three minutes. Use your bare fingers after testing for temperature or a test tube clamp to remove them to your test tube rack. Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 15 h. Record your results in Table 3. TABLE 3: INVERTASE ACTIVITY AT DIFFERENT pHs Test Tube Number pH of Test Solution 1 1.0 2 4.4 3 8.0 4 12.0 Benedict's Test Results: Benedict's Test Results: Precipitate Color (-, +, ++, +++, etc.) Question 12. At which pH was invertase most active? _______________ At which pH was invertase least active? _______________ Question 13. Thought question: Assuming yeast cells (from which your invertase was extracted) could survive pH 1.0 or pH 12.0, do your results suggest that they could obtain their energy from sucrose? Explain. Question 14. In the body of an organism such as yourself, do you expect all enzymes to operate effectively in the same pH range? For example: compare the pH of the stomach, where the digestive enzyme pepsin works, and the pH of blood, where other enzymes are found. What would you guess to be the normal pH inside of human cells, where there are many different enzymes? C. Experiment 3: Effect of a Possible Chemical Inhibitor (Iodine) on Invertase Activity In addition to various other environmental conditions, certain chemicals are known to inhibit the activities of many enzymes. In this exercise, your assignment is to determine whether an iodine solution inhibits the activity of invertase. Question 15. a. Name the enzyme to be used in your experiment: Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 16 b. Name the substrate to be used in your experiment: Question 16. What is the dependent variable of this experiment? Question 17. What is the independent (experimental) variable of this experiment? Question 18. State your hypothesis: Procedure: This time, you will design and execute your own experiment. However, since you will be using the same enzyme and substrate used in the temperature and pH experiments, many parts of your design will be the same. Remember that "good" science requires the use of a control. All test tubes should have contents as identical as possible, except for your experimental variable, iodine. Question 19. Describe what is meant by the phrase "controlled experiment." Now, design your controlled experiment for iodine. You will be led through the process as you answer Questions 17-22 below. When asked, write the quantities of materials you will place in the test tubes (“treatment levels”) in Table 4 on the next page. You have the option of using either two or three test tubes. Before you start your experiment, consider the following questions, and then check with your instructor. Question 20. Your instructor suggests that the total volumes in all tubes should be identical. Why? Question 21. What is the solvent in all of your solutions? How can the solvent be useful in designing your experiment? (Hint: See Question 19.) Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 17 Question 22. Some students decided to use the same pH buffer solution in all of their tubes. Why would this be useful? (Which buffer solution will you use? Why? (Hint: Review your results in Table 2.) Question 23. What temperature will you use for your experiment? Why? (Hint: Review your results in Table 2.) Question 24. Students have suggested that the enzyme be "pretreated" with the iodine before adding the substrate. Why would this be useful? (Hint: If you added the substrate to the enzyme first, think what might be happening while you were on your way over to the iodine bottle.) Question 25. How much time will you allow for the enzyme-substrate interaction before performing Benedict's test? Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) 18 Table 4: Experimental Design for Effect of Iodine on Invertase Activity (NOTE: THE QUESTIONS ON PAGES 14-15 WILL TELL YOU HOW TO COMPLETE THIS TABLE) Solutions Tube # 1 Tube # 2 Tube # 3 Contents Contents Contents ml. (or “drops”) of iodine 0 ml ml. enzyme (name: ________________) 2 ml 1 ml 3 ml 2 ml 2 ml ml. substrate (name: _______________) 2 ml 2 ml 2 ml ml. buffer (pH: _______________) 4 ml 4 ml 4 ml ml. DI water Total Volume Question 26. Results: execute your experiment as planned, then perform Benedict's test and enter your data in the table below. Tube # 1 Tube # 2 Tube # 3 Benedict's test results Question 27. Iodine experiment conclusions: a. Was your hypothesis supported, refuted or were your results inconclusive? b. Describe how analysis of your results led to your conclusion: Grossmont College Lab Manual, Fall 2020 edition Exercise 7 – Enzymes (6/2019) Question 28. You may be aware that iodine has been used as an antiseptic. What is an antiseptic? (Look up the definition.) Question 29. What have you learned about iodine to help you understand its use as an antiseptic? Grossmont College Lab Manual, Fall 2020 edition 19
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View attached explanation and answer. Let me know if you have any questions.hey buddy, here is your answer. In case you need anything else, do not hesitate to ask.

Exercise 7 – Enzymes (6/2019)

1

ENZYMES

Student Learning Outcomes
At the completion of this exercise, you should:
(1) Be able to describe how Benedict's test can be used to detect the presence of reducing sugars
like Glucose and Fructose.
(2) Be able to describe how enzymes, like Invertase, work on their substrates to produce
products.
(3) Be able to describe the general effect that temperature and pH have on the rate of an
enzyme’s activity.
(4) Be able to describe the question, hypothesis and results obtained in the temperature and pH
enzyme experiments.
(5) Be able to define pH and describe what a pH buffer is.

(6) Be able to design an experiment to test the effect of iodine on the activity of the enzyme
invertase.

I. Preliminary Observations
A. Introduction: General Information about Enzymes
Enzymes are substances which make it possible for organisms to carry out the variety of
metabolic activities necessary for life. Each of the numerous chemical reactions in a living
system is mediated by an enzyme. For example, in the lumen of the mammalian digestive tract,
especially the small intestine, large "food" particles are enzymatically broken down into
molecules small enough to be absorbed into the blood stream and thus carried to all the cells of
the body tissues. Also, within the individual cells, hundreds of different enzymes catalyze the
breakdown and syntheses of organic molecules in a continuing process which makes possible
cellular maintenance, growth and reproduction.

Grossmont College Lab Manual, Fall 2020 edition

Exercise 7 – Enzymes (6/2019)

2

Enzymes are just one of several categories of proteins. Each enzyme is a protein molecule that
is different in some respect from that of any other kind of enzyme. This uniqueness of structure
allows each type of enzyme to mediate only one specific chemical reaction, or at most a series of
very similar reactions. Enzyme molecules are also known to be very sensitive to their
environments. For example, exposure to high temperatures, chemicals such as strong acids and
other factors often can denature an enzyme's structure, making it unable to carry out its
function. An enzyme can therefore act only if it is structurally intact, and only within a limited
range of environmental conditions.
Enzymes act as biochemical catalysts. It is thought that their presence reduces the activation
energy necessary to start a chemical reaction. The rate at which the chemical reaction proceeds is
therefore accelerated, and the end products are formed more rapidly. The enzyme molecule itself
remains unchanged during the reaction and does not become a part of the end products.
Therefore, enzymes are reused, as the same enzyme molecule may perform the same function
many times, each time converting a new substrate molecule into the same kind of product
molecule.
B. The Enzyme Invertase: A Representative Example for Today's Studies
The enzyme invertase has been selected as a representative example for demonstrating the
effects of some environmental factors on enzyme activity. (Enzyme names often have the suffix
"-ase.") The Invertase which we shall use in this experiment was produced by yeast, a singlecelled organism (actually a kind of fungus). In humans, a similar enzyme (called sucrase),
produced by the pancreas, operates in the small intestine.
The specific reaction that Invertase catalyzes is the breakdown of the double sugar
(disaccharide) sucrose into the two simple sugars (monosaccharides), glucose and fructose. It
accomplishes this by rupturing the chemical bond that links the simple sugars in the sucrose. The
reaction can occur only in the presence of water: one molecule of water is required to break apart
the disaccharide and, by so doing, completes the structures of the monosaccharides. Breakdown
of molecules with the addition of water is called hydrolysis. This same reaction occurs routinely
in the human small intestine and allows the absorption into the bloodstream of carbohydrates as
monosaccharides.

Substrates

Products

Grossmont College Lab Manual, Fall 2020 edition

Exercise 7 – Enzymes (6/2019)

3

Question 1. Any enzyme converts substances generally known as substrates into substances
commonly called products. For the reaction shown above, name the substrates and products
below. Then label them on the drawing above.
a.

substrate(s): sucrose

b.

product(s): glucose and fructose

Question 2. If a student mixes some sucrose and Invertase solutions in a test tube and allows
some time for reaction, what results would you predict?
The reaction should generate glucose and fructose as products.

C. How to Tell If Invertase Has Done Its Job: Benedict's Test
1. Why Do We Need Benedict's Test?
Of course, we cannot see the enzyme invertase in solution, as it is colorless. As you may
already know, neither can we see the sugars sucrose, glucose or fructose when they are
dissolved. However, we do wish to measure the rate at which Invertase catalyzes the
hydrolysis of sucrose into glucose and fructose. Clever ways to do this might include a
chemical test to reveal the presence or absence of sucrose or a different test for the
products of the reaction. Fortunately, biochemists have developed such a technique,
called Benedict's test. This test uses a special solution of chemicals - called Benedict's
reagent a clear, blue solution w...


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