ENZYME LABS
Without enzymes chemical reactions in cells would progress at a snails pace and life
would cease to exist. For example, without enzymes it would take six months to
digest one Hershey bar.
Learning expectations:
1. What is an enzyme?
2. Are enzymes specific?
3. Are enzymes used up in chemical reactions?
4. What are enzymes mostly made of?
5. How do enzymes work?
6. How will changes in the cells physical or chemical environment (temperature or
pH) affect enzyme activity?
EXPERIMENT 1-WHAT CLASS OF BIOMOLECULES ARE ENZYMES & WHAT ARE
THE FUNCTIONS OF ENZYMES?
MATERIALS:
3 test tubes
Test tube rack
Brush
Sharpie
0.1% amylase solution
Iodine
Benedicts
Starch solution
PROCEDURE:
PART A:
1. Label two test tubes as follows:
a. Starch and iodine
b. Starch and benedicts
2. Add 1 ml of starch to each tube
3. To test tube labeled starch and iodine add 5 drops of iodine and record any
color change
4. To test tube labeled starch and Benedicts add 1 ml of Benedicts, place in hot
water bath for five minutes, and then record any color change
5. Clean test tubes
ANALYSIS QUESTIONS:
1. Does starch contain any monosaccharides?
2. Is starch a polysaccharide?
1
PART B:
1. Label three test tubes as follows:
a. Amylase and iodine
b. Amylase and Benedicts
c. Amylase and Biurets
2. Add 1 ml of amylase to each tube
3. To test tube labeled amylase and iodine add 5 drops of iodine and record any
color change.
4. To test tube labeled amylase and Benedicts add 1 ml of Benedicts, place in
hot water bath for five minutes, and then record color change.
5. To test tube labeled amylase and Biurets add 1 ml of Biurets and record any
color changes.
6. Clean test tubes
ANALYSIS QUESTIONS:
1. Is amylase a starch?
2. Is amylase a monosaccharide?
3. Is amylase a protein?
PART C:
1. Label two test tubes as follows:
a. Amylase, starch, & iodine
b. Amylase starch & Benedicts
2. Add 1 ml of starch to both test tubes
3. Add 1 ml of amylase to both test tubes
4. Allow the test tubes to sit for five minutes
5. Add 5 drops of iodine to test tube labeled Iodine and then record any changes
in color
6. Add 1 ml of Benedict’s to test tube labeled Benedict’s, place in hot water bath
for five minutes, and then record color change.
ANALYSIS QUESTIONS:
1. What is the function of amylase?
2. Using the data from Part A, B, and C explain how you came up with your
answer for question 1.
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EXPERIMENT 2: ARE ENZYMES SPECIFIC, WHAT ARE THE FUNCTIONS OF
ENZYMES, AND WHAT IS THE AFFECT OF TEMPERATURE ON ENZYME
FUNCTION?
MATERIALS:




Enzyme
solution
15ml
milk/lactose
Water
Sucrose
solution




Boiled enzyme
solution
100ml
graduated
cylinder
10ml graduated
cylinder
5 test tubes





Test tube rack
Marking pencil
Hot plate with
500 ml beaker
with water
Benedicts
solution
Stirring rod
Introduction
 Both lactose and sucrose are disaccharides and both have the exact chemical
formula C12H22O11
 Lactose, the sugar found in milk, is composed of glucose and galactose.
 Sucrose, ordinary table sugar, is composed of fructose and glucose.
 Lactase is an enzyme that breaks lactose down into galactose and glucose.
 People who are lactose intolerant can purchase lactase in pill form. These
people lack the enzyme, lactase, and cannot break down the sugar lactose
into its component parts.
Since lactose is similar to sucrose, can lactase also break down
sucrose?
PROCEDURE:
1. Label the five test tubes with the following labels:
a. Test tube with skim milk and enzyme solution
b. Test tube with skim milk and water
c. Test tube with skim milk and boiled enzyme solution
d. Test tube with sucrose solution and enzyme solution
e. Test tube with sucrose solution and water
2. In test tube “a” add 2ml of skim milk and 1ml of enzyme solution
3. In test tube “b” add 2 ml of skim milk and 1ml of water.
4. In test tube “c” add 2ml of skim milk and 1ml of boiled enzyme solution
5. In test tube “d” add 2ml of the sucrose solution and 1ml of enzyme solution
6. In test tube “e” add 2 ml of the sucrose solution and 1 ml of water
7. Add 1 ml of Benedicts solution to each test tube, place all five test tubes in
hot water bath for five minutes, and then record color change.
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ANALYSIS QUESTIONS:
1. What is the function of lactase?
2. Explain your answer to number 1 from the results of your experiment/
3. Is the enzyme lactase specific?
4. Depending on your answer to 3, why did the enzyme either react to both
lactose and sucrose or react to only lactose? Explain
5. How did the high temperature of boiling affect the enzyme activity?
6. Give an explanation for your answer to # 5
7. In this experiment a disaccharide was broken down into two
monosaccharides by an enzyme. Was this reaction hydrolysis or
dehydration synthesis?
EXPERIMENT 3: ARE ENZYMES REUSABLE OR USED UP IN A CHEMICAL
REACTION?
MATERIAL:
2 test tubes
Test tube rack
Liver
Hydrogen Peroxide
10 ml graduated
cylinder
Dropper
Stirring rod
INTRODUCTION:
 Your cells are always making poisonous chemicals. They do not die because
your cells use enzymes to break down these poisonous chemicals into
harmless substances.
 Catalase is an enzyme that speeds up a reaction, which breaks down
hydrogen peroxide, a toxic chemical, into 2 harmless substances--water and
oxygen.
The reaction is: 2 H2O2 ----> 2 H2O + O2

 This reaction is important to cells because hydrogen peroxide (H2O2) is
produced as a byproduct of many normal cellular reactions. If the cells did
not break down the hydrogen peroxide, they would be poisoned and die.
 Catalase is found in liver cells. It might seem strange to use dead cells to
study the function of enzymes. This is possible because when a cell dies, the
enzymes remain intact and active for several weeks, as long as the tissue is
kept refrigerated.
PROCEDURE:
PART A: Observe Normal catalase reaction
1. Place 2 ml of hydrogen peroxide into a clean test tube
2. Add a small piece of liver to the test tube and push into the hydrogen
peroxide with a stirring rod.
3. Observe the bubbles and use the scale below to record your observation _____
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QUALITATIVE DESCRIPTION OF CATALSE REACTION
Description
No reaction
Slow release of bubbles
Steady release of bubbles
Fast and many bubbles, not overflows
test tube
Very rapid and many bubbles, overflows
test tube
BUBBLE
SCORE
0
1
2
3
4
PART B:
1. Pour off the liquid from the test tube in part A into a second test tube
2. Add another 2 ml of hydrogen peroxide to the liver in the first tube (original
tube).
3. Using the table above record your observations _________
ANALYSIS QUESTIONS:
1. Is catalase reusable?
EXPERIMENT 4: WHAT IS THE AFFECT OF TEMPERATURE ON ENZYME
ACTIVITY?
MATERIALS:
Liver
37 C water bath
Ice
Hydrogen peroxide
5 test tubes
Test tube rack
Water
Thermometer
Hot plate
500 ml beaker
PROCEDURE:
PART A:
1. Label one test tube “liver 100 C”
2. Add a small piece of liver to test tube
3. Cover the liver in test tube with a small amount of water
4. Boil test tube for five minutes and measure temperature (record)
5. Remove from boiling water and allow it to cool
6. Pour out the water
7. Add 2 ml of hydrogen peroxide and record observations ______
8. Pour off liquid and allow the temperature to return to room temperature
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9. Add 2 ml of hydrogen peroxide to room temperature liver and record
observations ______
PART B:
1. Label test tubes as follows:
a. Liver 37 C
b. Liver 0 C
c. Hydrogen peroxide 37 C
d. Hydrogen peroxide 0 C
2. Add a small piece of liver to test “a” and “b”
3. Add 1 ml of hydrogen peroxide to test tubes “c” and “d”
4. Place the two test tubes labeled 37 C in a 37 C water bath
5. Place the two test tubes labeled 0 C in a ice bath
6. Wait five minutes and measure temperature (record)
7. Pour the 37 C hydrogen peroxide into the 37 C liver and record your
observations _________
8. Pour the 0 C hydrogen peroxide into the 0 C liver and record your
observations _________
9. Pour off liquid from 0 C test tube and allow the temperature to return to
room temperature
10. Add 2 ml of hydrogen peroxide to room temperature liver and record
observations ______
ANALYSIS QUESTIONS:
1. What is the effect of very cold temperatures on enzyme activity?
2. What is the effect of warm temperature on enzyme activity?
3. What is the effect of very hot temperatures on enzyme activity?
4. Can enzymes at very high temperature regain their function when returned
to normal temperatures?
5. Can enzymes at very low temperature regain their function when returned to
normal temperatures?
6. Explain why for the answers to questions # 4 and 5
EXPERIMENT 5: WHAT IS THE AFFECT OF pH ON ENZYME ACTIVITY?
MATERIALS:
Liver
Hydrogen peroxide
1M HCL
1M NaOH
pH probe/paper
3 test tubes
Test tube rack
PROCEDURE:
1. Label 3 test tubes as followed
a. Acid pH
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b. Basic pH
c. Neutral pH
2. Add 2 ml of hydrogen peroxide to each of the three test tubes
3. Add 10 drops of HCL to test tube labeled “acid pH”
4. Test pH with probe or pH paper and record _________
5. If you do not have a pH below 5 add more drops of HCL until you have a pH
below 5
6. Add 10 drops of NaOH to test tube labeled “Basic pH”
7. Test pH with probe or pH paper and record _________
8. If you do not have a pH above 9 add more drops of NaOH until you have a pH
above 9
9. Add 2 ml of water to test tube labeled “neutral”
10. Test pH with probe or pH paper and record _________
11. Add a small piece of liver to each test tube and record your observations
below:
EFFECT OF PH ON ENZYME ACTIVITY
Type of environment for enzyme
Bubble score
Acid pH
Basic pH
Neutral pH
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