Determine the Functions of Digestive Enzymes in Breading Down Starch (page 3)
Design Your Own Experiment
- Food is transported from the mouth to the stomach and on through the digestive tract by a motion known as peristalsis. The smooth muscles in the walls of the digestive organs squeeze and contract in a wavelike motion that pushes the food ahead of the contracted area. Demonstrate peristalsis motion in the esophagus by moving a marble through a rubber tube in which the marble fits tightly. Push on the tube behind the marble (see Figure 26.3). Use a diagram to compare the movement of the marble through the rubber tube to movement of a bolus (wet ball of partially digested food) through the esophagus.
- Does the shape of an intestine increase absorbency? Folded paper towels take up less space but can absorb more liquid as do the folds in the lining of the intestine. Demonstrate this by folding one paper towel in half four times to form a small square. Prepare a measuring jar by placing a piece of masking tape down the side of the jar. Fill the jar with water and mark the water level. Dip the folded paper square into the jar of water. Remove the paper and mark the new water level. Refill the jar to the first water level and dip a paper square made with three folded paper towels. Compare the difference in the water removed by the two squares. More information about this can be found in the experiment titled "Folds" (p. 98) in Janice VanCleave's Biology for Every Kid. (New York: Wiley, 1990).
Get the Facts
Learn more about the digestive system. Use a biology text to examine the structure and function of each organ in the system. Find out about the chemical changes that occur and the chemicals involved in promoting the changes (such as amylase, gastric juices, and bile). What is the difference between a bolus and a chyme? Where are most of the nutrients from the food absorbed into the bloodstream and lymph system? How long does it take for the stomach to empty after a meal?
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