AskERIC Lesson Plans
Lesson Plan #:AELP-BIO0024


An AskERIC Lesson Plan

AUTHOR: Margaret Childers, Nampa Senior High

GRADE LEVEL/SUBJECT: 10th grade Biology


 Enzymes are proteins that speed up or slow down a chemical reaction and are not consumed by the reaction. They play an important role in the living process. The most easily understood use of enzymes is in the digestive process. Digestion can include nutritious molecules or potentially harmful molecules like alcohol. Students will use active enzymes in their saliva to demonstrate how enzymes work on common food molecules. They are also asked to apply this concept to alcoholism.


 The activity will demonstrate enzyme activity and how changes in the physical conditions affects their performance. Students will work with active enzymes and explore the boundaries of their activity.

OBJECTIVES: (The student will be able to:)

  1. define enzyme
  2. observe enzyme activity
  3. explain how changing the physical conditions affects enzyme activity
  4. discuss the relationship between drug use and enzyme activity
  5. explain the enzyme deficiencies of an alcoholic

 Starch solution, 6 test tubes, Benedict's solution, Iodine solution, hot water bath


  1. Demonstration - add hydrogen peroxide to separate beakers containing potato cubes and liver extract. Have students list their observations and formulate an explanation. As a group discuss enzymes and how they react.
  2. Perform the lab activity and answer the lab questions
TYING IT ALL TOGETHER: Using a minimum of 50 words, answer the following questions.
  1. What are some of the important properties and characteristics of enzymes?
  2. Explain the action of the saliva on the starch. How does this affect digestion in your body?
  3. What happens to enzyme activity when the physical conditions are changed?
  4. Alcoholics do not produce the enzyme needed for the digestion of alcohol. How will this affect their ability to metabolize alcohol?
Discuss the opening demonstration allow students to changetheir explanation of enzyme activity. Discuss the objectives and the lab activity.


Before you start you will need to set up a chart that lists testtubes #1 - #6. Leave room for a description of the test tube contents and your observation of results.


  1. Spit into a test tube, filling it one-fourth full of saliva. All lab group members may contribute to this effort. It may help to think about mouth-watering food while contributing (lemons). Sometimes something inedible, such as a rubber band, helps. Do not put any food or drink other than water into you mouth for at least two hours preceding this laboratory. Otherwise you will contaminate your sample.
  2. Add an equal amount of water to the spit in the test tube, and gently mix it all together.
  3. Number the remaining test tubes #3 - #6.
  4. Add 5 ml. starch solution to each of the test tubes #3 - #6.
  5. Add 1 ml. saliva solution to test tubes #3 and #4. Allow both test tubes to set for five minutes.
  6. While these test tubes are setting, place remaining saliva solution in the water bath.
  7. Add 3 drops of iodine solution to test tubes #1 & #3. Record your observations.
  8. Add 10 drops of Benedict's solution to test tubes #2 . Heat these solutions in the hot water bath for five minutes. Record your observations.
  9. Add 1 ml. boiled saliva solution to test tubes #5 and #6. Allow both test tubes to set for five minutes.
  10. Add 3 drops of iodine solution to test tube #5. Record your observations.
  11. Add 10 drops of Benedict's solution to test tube #6. Heat this solution in the hot water bath for five minutes. Record your observations.
Answer the following questions, summarizing the lab.
  1. What conclusions can you reach about the action of salivary enzymes on the digestion of starch?
  2. What varied in the treatment of test tubes #1 and #3? Why is this difference important in your conclusion?
  3. How did heating the saliva solution affect the action of the saliva?

May 1994

These lesson plans are the result of the work of the teachers who have attended the Columbia Education Center's Summer Workshop. CEC is a consortium of teacher from 14 western states dedicated to improving the quality of education in the rural, western, United States, and particularly the quality of math and science Education. CEC uses Big Sky Telegraph as the hub of their telecommunications network that allows the participating teachers to stay in contact with their trainers and peers that they have met at the Workshops.

This activity has been copied, with permission, from the Educational Resources Information Center (ERIC) server to ours, to allow faster access from our website. We encourage you to explore the original site.

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