Toxicology reports ordered during Anna’s autopsy reveal that Anna had high amounts of glucose in her blood at the time of her death. This finding suggests that Anna most likely ate a large meal near the time of her death. In the first lesson of this unit, you explored the relationship between blood glucose and diabetes. Glucose levels are related to the food we consume. Given that Anna was a diabetic, she had to think carefully about her diet and choose her foods wisely. Analysis of her stomach contents at the time of her death may reveal information about Anna’s last meal and provide additional evidence regarding the conditions surrounding her mysterious death.
Eating a balanced diet is necessary for good health. The main nutrients in our food are classified as carbohydrates (sugars and starches), lipids (fats and oils), and proteins. Carbohydrates, including simple sugars such as glucose, are a great source of energy. Proteins are crucial in our diet as they help build tissue, fight disease, and facilitate chemical reactions. Lipids, commonly called fats, have equally important functions, including cell membrane and hormone production. An adequate amount of each of these nutrients is needed to keep the body in balance. In this project you will perform chemical tests to determine what foods contain carbohydrates, lipids, and proteins.
Scientists analyze the chemical components of a substance in a variety of ways; one of the simplest methods is to use chemical indicators. An indicator is a substance that changes to indicate the presence of a particular compound or type of compound. The indicator may change color or temperature or may produce some other substance, such as bubbles or a distinctive odor. The change in the indicator is due to a chemical reaction between the indicator and the tested substance. Indicators are very specific and function based on the chemical compositions of the indicator and the substance being detected. Some indicators are sensitive to temperature, pH, and other environmental conditions. Generally, the easiest indicators to use are ones that change color to indicate the presence of a substance.
In Project 2.2.1 you will use chemical indicators to tests for the presence of sugar, starch, protein, and lipids in three common food items as well as in the stomach contents of the ill-fated Anna Garcia.
Positive controls for each test:
Starch solution, 5% corn starch or other starch soluble in water
Protein solution, 5% albumin in water
Sugar solution, 5% glucose in water
Lipid solution, cooking oil
Anna Garcia simulated stomach contents
Project 2.2.1 Autopsy Report resource sheet
Project 2.2.1 Anna Garcia Food Diary resource sheet
3 small samples of food
200 mL of distilled water in a beaker
8 transfer pipettes
Hot plate with beaker containing distilled water (to make a hot water bath)
12 test tubes
Test tube rack
Test tube holder
Test tube brush
1 beaker, 250 mL
1 beaker, 500mL
1 graduated cylinder, 10mL
Mortar and pestle (optional)
Lugol’s Iodine stain
Brown paper, multiple pieces, approximately 2 to 3 cm square
2 stirring rods
PBS Course File
Part I. Positive Controls—Standard Positive Tests
1. Obtain a Project 2.2.1 Autopsy Report resource sheet from your teacher. Read updated information from Anna’s autopsy. Highlight any information you feel requires further investigation and record them as notes in a fresh page of your laboratory journal. Make sure to record them on a fresh page titled “2.2.1 Food Testing.”
2. Obtain a Project 2.2.1 Anna Garcia Food Diary resource sheet. Note that because Anna was a diabetic, she kept a detailed record of her food intake. Scan the document that covers the two days before she died and the morning of her death. Note any obvious differences between the first and second day. Also note that the…