Biology 215 Labs: Digestive Enzymes

Bio 215 Home Lab Schedule

In this laboratory, you will investigate a few of the many enzymes used during digestion. You will discover which enzymes a cockroach has in its digestive tract, and how this system compares to mammals. Answer the questions below and in the "For further thought..." section to better prepare you for the laboratory session.

Amylase...The test for amylase is a test for starch. After adding the enzyme (body fluid) to the medium (starch) you will periodically test for the presence of starch by mixing a drop of iodine with the solution in a spot plate.

Protease...The test for protease is done by placing drops of the body fluid on stips of unexposed film. The dull side of the film is an emulsion (protein) layer. If protease is present in that section of body fluid, the film should be digested and a transparent spot should appear. To determine which section of the body has the most protease, the 3 separate strips of film are used. They are tested at 6-hour intervals by washing them off and checking for transparency.

Sucrase...The test for sucrase, or the digestion of sucrose, a double sugar is to test for the presence of simple sugars, or reducing sugars. At the end of the test, the test tube with the most precipitate has the greatest amount of reducing sugars, and therefore the most sucrase.

Lipase...The test for lipase involves mixing a fat (oil) with the body fluid samples, and checking for a pH change. As the fats are digested, acids are released. Due to the pH indicator phenol red, the color in the test tubes should change from red to yellow as the fat is digested.

For Further Thought...

1. Where in the mammalian digestive system would you expect to find the most enzyme activity?

2. Which part of the insect's digestive system is designed to retain water for the animal?