Begin class with a discussion of food and the food groups. Each of the major organic molecules can be correlated to different classes of foods (protein = meat and beans group, simple sugars (glucose and fructose) = sweets and fruit groups, complex carbohydrates (starch) = grains group, lipids = fats group). Allow this discussion to lead into the idea that all food items are made up of building block organic molecules. Food items were all once alive. Therefore, all living things are made up of these same building blocks that our food is made of.
Go into as much detail as necessary for your students on the biochemistry of organic molecules. You may want to describe the relationship between glucose and starch at this time.
Pass out the student lab handouts. Describe the activity to your students. Each student will test solutions at 3 different stations. They should choose one solution from each of the following categories: “never alive”, “once was alive” and a mystery solution. They will be testing for protein, starch and glucose. In addition to the 3 solutions you will carry around with you, there will also be a 4th solution at each test station. This is one that is guaranteed to cause a color change so that you know what a color change looks like.
Show students any special procedures, such as how to prepare the hot water bath. Answer any questions.
Allow students 5 minutes to gather their materials and then 10-15 minutes at each test station. Help groups that are having difficulty.
When all testing is complete and teams have cleaned up, create a master table on the board like the one below to collect all the teams results for all the different tests.
Fish tank water (pond water)
Unsweetened powdered lemonade
Discuss the results paying close attention to how to correctly draw conclusions regarding whether a item was once alive or not.
Bring things back to the idea of food. Discuss what protein, starch, and glucose are for, why our bodies need them, and where we get those nutrients from. Discuss how other creatures such as plants, bacteria, and fungi obtain these nutrients.