Unit D

Module 6 ~ Lesson 1


Enzymes are specific types of proteins that help regulate the many different chemical reactions that occur in your body. Enzymes lower the activation energy required to catalyze reactions. Otherwise, the energy required would be too large and these reactions could cause damage to your body's cells. 

Enzyme function can be simply described as the speeding up of a chemical reaction due to the interaction of an enzyme's active site with a specific substrate molecule or molecules.

For example, the enzyme lactase only binds to the substrate molecule of lactose.


As you watch the video below, notice how the active site of the enzyme changes shape slightly as the enzyme performs its function. This is sometimes known as the induced fit model of enzyme activity.

Remember that hydrolysis is the decomposition of a compound by a reaction with water. The hydrolysis of sucrose into its components of glucose and fructose is controlled by the enzyme sucrase, which is found in the human digestive tract. As you watch the video, note how the enzyme never actually becomes part of the reactants or products of the reaction. The enzyme can be used over and over.

One factor that affects enzyme action is inhibition. This next animation illustrates how the end products of a series of enzymatic reactions will inhibit enzyme activity in a negative feedback loop.  Feedback inhibition ensures that the body doesn't needlessly produce more products of the biochemical pathway than are needed.



An enzyme will no longer work if it is denatured by heat or low pH. Activity is also decreased when the temperature is too low to allow flexibility in enzyme molecules.


Read "Enzymes" on pages 214 to 216 of your textbook.