In the Biology EOC, Performance Indicator 3210.1.5: "Identify how enzymes control chemical reactions in the body" is used to create the following ADI.
Step 1: Identification of the Task
The ADI will be introduced by teaching students the basic structure and function of enzymes. Students should already understand the concept of pH and titration and know how to pipette properly. They should kmow how indicators work and how to use pH strips. There will also be a short lesson introducing the hydrolysis of starch to glucose that occurs in the mouth and the small intestine.
The problem: The enzyme amylase reacts with starch and facilitates the hydrolysis of starch into glucose, which is usable by the body. However, amylase is only active in the mouth and in the small intestine but not in the stomach. Why is amylase inactive in the stomach? What about the stomach is different from the mouth and small intestine?
Step 2: Generation of Data
Students will be broken into lab groups and each given two beakers, one with a neutral pH of 7.0 and another with a pH of 2.0. The beakers will have starch and IKI dissolved in solution, which stains starch blue-black. Originally, both beakers will be blue-black. The students will be instructed to take a pH test of both beakers and record this information. They will then dissolve amylase into each beaker and record what happens to the color. If the starch is hydrolyzed by the amylase into maltose and maltotriose, then the solution will no longer be blue-black as IKI does not stain these sugars. If the starch has not been hydrolyzed enough, the solution will remain the same blue-black color.
Step 3: The Production of a Tentative Argument
Students will get in groups and develop an argument for why they think amylase is inactive in the stomach but active in the mouth and small intestine.
Students will be share their ideas and discuss them with other groups. They will be encouraged to research the mouth, stomach and small intestine in order to back up their arguments. They will be given a chance to revise their models based on the feedback of other groups and finally the entire class will discuss their findings together.