4 Chapter 4
LAB 4
Introduction to the Digestive System
Prepared by Jason R. Jones, University of North Alabama
OBJECTIVES
After completing these laboratory activities, you should understand / be able to:
- Recognize the organs of the digestive system, including those that are part of the alimentary canal or digestive tract, as well as those that are considered accessory organs, and their functions.
- The difference between mechanical digestion and chemical digestion.
- Define the terms catalyst, enzyme, and substrate.
- That enzyme activity can be affected by multiple factors, and examples of such factors affecting enzyme activity.
- Define the terms positive control and negative control, and know how/why they are important.
- Define the term peristalsis.
- Some of the major digestive enzymes involved in digestion of carbohydrates, proteins, and fats; know where these enzymes are produced, and the site of their actual function.
- Different factors that can affect the activity of digestive (and other) enzymes.
- The role of bile in the emulsification of fats.
INTRODUCTION
The digestive system is responsible for processing the food taken into the body and converting it to usable energy.
The process of digestion can actually be divided into two main types of digestion. The first of these is mechanical digestion, which is simply the breaking down of food into smaller pieces, but without any chemical changes to the food. This process is begun in the mouth, through the chewing action of our teeth. By chewing food into smaller pieces, this increases the surface area of the food. This larger surface area thus provides for faster and more efficient chemical digestion (which also begins in the mouth), in which various enzymes actually further break down the food chemically into smaller molecules that are more easily absorbed and used by our bodies for various functions. An enzyme is an organic molecule (usually a protein) that acts as a catalyst (a molecule that speeds up a particular reaction) for the breakdown of large molecules in our food into smaller “building block” molecules. Enzymes are usually very specific, and a given enzyme typically only speeds up a single type of reaction. Enzymes speed up reactions by binding to a substrate, which is one of the reactants in a chemical reaction.
In these exercises, you will familiarize yourself with the anatomy of the digestive system, including the organs of the alimentary canal (or digestive tract) and the various accessory digestive organs that also play important roles in digestion. You will also examine the activity of several digestive enzymes, as well as explore factors that may affect the activity of these enzymes.
Figure 1. Organs of the digestive system
ACTIVITY I: Organs of the Alimentary Canal
When most people think of the digestive system, they typically think of the digestive tract, also known as the alimentary canal, though there are other organs that function in digestion (the accessory digest