A. TWO DEFINITIONS
CATALYST = a substance that increases the rate of a chemical reaction and is not
changed by the reaction
ENZYME = a protein that functions as a biological catalyst
B. THE LOCK AND KEY MODEL
substrate products released
active site
enzyme enzyme-substrate enzyme
complex (unchanged)
• Each enzyme has an active site that is a specific shape
• The active site is a complementary shape to its substrate
• The substrate binds to the active site, forming an enzyme-substrate complex
• Bonds are weakened in the substrate
• Activation energy for the reaction is lowered
• Products are released and the enzyme is unchanged
CATALYST = a substance that increases the rate of a chemical reaction and is not
changed by the reaction
ENZYME = a protein that functions as a biological catalyst
B. THE LOCK AND KEY MODEL
substrate products released
active site
enzyme enzyme-substrate enzyme
complex (unchanged)
• Each enzyme has an active site that is a specific shape
• The active site is a complementary shape to its substrate
• The substrate binds to the active site, forming an enzyme-substrate complex
• Bonds are weakened in the substrate
• Activation energy for the reaction is lowered
• Products are released and the enzyme is unchanged
