Enzyme Specificity: Adventures in Digestion

Chemistry Activity
Enzyme Specificity
Adventures in Digestion

Introduction

This lab is actually three separate activities. To make this page easier to navigate, it has been broken up into sections. This page contains the introduction, while the three lab activities are given their own pages.
Enzyme Specificity Menu
Introduction
Activity #1: Digestion of Protein
by Tripsin
Activity #2: Digestion of Lipids
by Lipase
Activity #3: Digestion of Starch
by Amylase
General Safety Guidelines
Microbiology Safety Guidelines

Enzymes are proteins that can act as powerful catalysts to speed up important chemical reactions in your body. Sometimes, the enzyme can't act on its own, but has to be “switched on” by coupling with a much smaller molecule, called a substrate. The molecular structure of a substrate matches that of the enzyme so that the substrate can fit into the enzyme molecule like a key in a lock. Without the match, the enzyme is not able to accelerate a particular chemical reaction. In the series of labs that follow, you will determine if a particular enzyme matches a particular substrate by chemically detecting the specific end products of the reaction that the enzyme catalyzes. In the case of the enzyme amylase, end products will be simple sugars, broken off of larger sugars (di-, tri-, and polysaccharides). For the enzyme lipase, the end products will be carboxylic acids. You will measure the production of these acids by monitoring changes in pH of the reacting solution. For the enzymes called proteases, products produced from breakdown of larger protein molecules include amino acids. But their presence is determined indirectly based on the fact that the larger protein molecules are able to stick together to produce the solid state (gel) at room temperature. If the protein molecules are “digested,” or chemically broken apart into smaller units of amino acids, the solid state is lost and the breakdown products form a liquid. It is this change in physical state that will be used to indicate successful enzyme activity.

The chemical environment in which enzymes operate is varied. In the investigations that follow, you need to pay attention to the combination of materials, their concentration, the pH of the resulting solution, and the temperature of the mix. Each of these variables can be tested separately.

Finally, since we are using enzymes derived from the human digestive tract, the ideal pH for each enzyme will be different. This is because different parts of your digestive tract operate at different pH levels. For example, your mouth is mildly acidic with a pH seldom less than 6.0, while your stomach is very acidic with a pH of 1.0.

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