Activity 10A (Lab Activity)
Changing the Starch in “Yams” to Sugar
|Lesson Overview||This lab activity provides students with the experience of using their own enzymes to convert starch to sugar (a disaccharide called maltose), then testing to see if the conversion has taken place.|
|Learning Objectives||Students will learn how to set up an experiment that includes a control, apply lab data to test the concept that starch can be changed (converted) to a sugar, and to determine if that conversion has taken place.|
This activity includes chemical reactions with an enzyme (amylase), establishing standards for detecting the existence of reactants or product(s)starch and sugar (maltose)and for utilizing a control.
|Skills Required||Students should be able follow printed instructions and respect safety guidelines while working.|
This exercise will require two 40-45 minute periods, the student’s time to complete the homework assignment, and class time to discuss the homework assignment.
|Student Ability Level and Grouping||Students of all abilities can work in groups of pairs through a maximum of 4 students.|
|Pre-lab||Students should be instructed in the purpose of using reference standards (starch and sugar tests) and a control. Also, students should be instructed in the safe removal of test tubes from a water bath.|
|Post-lab||It is important that the class come together to compare results and to make sure that students understand what was going on in the test tubes. Ask them why they were asked to wait 30 minutes before testing for starch and sugar. Also, what does a negative test for starch in test tube #3 mean? Why would there be less or no starch in test tube #3 after 30 minutes? If test tube #5, the control (no saliva), shows a positive test for sugar, how would you explain this? (There may be some starch that breaks down with out an enzyme.)|
Students should respond in writing to the questions posed in the lab exercise as homework, and the class as a whole should discuss the responses of individual groups the following day.
|Student Resources for Further Study||
This lab exercise relates to many different topics, including digestive enzymes (in the broader category of catalysts) and agriculture involving the production of tuber crops, including both yams and sweet potatoes. This lab is also related to the work of Percy Julian in the sense that he worked with yams from Guatemala and Mexico to extract the toxin called diosgenin. This chemical was then used as a base chemical to be converted to cortisone and several important hormones including estrogen, progesterone, and testosterone at a price that made these pharmaceuticals available to most people.
This activity meets the following National Science Education Standards (Grades 5-8) and Curriculum Standards for Social Studies.
National Science Education Standards (Grades 5-8)
Science as Inquiry
Science and Technology
History and Nature of Science
Curriculum Standards for Social Studies