he digestive system is a physiological marvel, composed of finely orchestrated chemical and physical activities. The food we ingest must be broken down to its molecular form for us to get the nutrients we need, and digestion involves a complex sequence of mechanical and chemical processes designed to achieve this goal as efficiently as possible. As food passes through the gastrointestinal tract, it is progressively broken down by the mechanical action of smooth muscle and the chemical action of enzymes until most nutrients have been extracted and absorbed into the blood.
1. To list the digestive system enzymes involved in the digestion of proteins, fats, and carbohydrates; to state their site of origin; and to summarize the environmental conditions promoting their optimal functioning. 2. To recognize the variation between different types of enzyme assays. 3. To name the end products of digestion of proteins, fats, and carbohydrates. 4. To perform the appropriate chemical tests to determine if digestion of a particular food has occurred. 5. To cite the function(s) of bile in the digestive process. 6. To discuss the possible role of temperature and pH in the regulation of enzyme activity. 7. To define enzyme, catalyst, control, substrate, and hydrolase. 8. To explain why swallowing is both a voluntary and a reflex activity. 9. To discuss the role of the tongue, larynx, and gastroesophageal sphincter in swallowing. 10. To compare and contrast segmentation and peristalsis as mechanisms of propulsion.
Chemical Digestion of Foodstuffs: Enzymatic Action
Nutrients can only be absorbed when broken down into their monomer form, so food digestion is a prerequisite to food absorption. Enzymes are large protein molecules produced by body cells. They are biological catalysts that increase the rate of a chemical reaction without becoming part of the product. The digestive enzymes are