Class Notes
Topic: Enzymes
Questions/Main Idea:
Name: _______________________________________
Period:_______________________________________
Date: _______________________________________
Notes:
What are enzymes?
• Enzymes are proteins that help molecules react with one
another
• Their monomers are amino acids.
• Enzymes are used by cells to trigger and control
chemical reactions.
• Without enzymes, several reactions in cells would never
occur or happen too slowly to be useful.
• In digestive enzymes, often end in “-ase”
What is a chemical
reaction?
• It is the process of changing one set of chemicals
(reactants) into another set of chemicals (products) by
rearranging the atoms.
• Reactants’ bonds are broken and new ones are formed in
the products.
What is a catalyst?
• It is a substance that speeds up the rate of a chemical
reaction.
• It lowers the activation energy.
• It participates in the reaction but doesn’t change itself;
therefore it can be used over and over.
What is activation
energy?
• It is the amount of energy needed to start a chemical
reaction.
• Catalysts speed up chemical reactions by lowering their
activation energy.
• Enzymes are catalysts because they lower the activation
energy by holding molecules together to either help them
bind (synthesize) or help them break apart (decompose).
What is a substrate?
• Enzymes bind to or break molecules called substrates.
• These substrates are the reactants that are catalyzed by
the enzyme.
What is the active site?
• Each substrate and enzyme has a specific shape,
therefore enzymes bind to substrates based on shape.
• The site on the enzyme where the substrates bind is
called the active site.
What is the Lock and Key
Hypothesis?
• Enzymes bind to the substrates based on their
complementary shape.
• The fit is so exact that the active site and substrates are
compared to a lock and key.
• Most digestive enzymes are named for the foods
(molecules) they help react—lactase helps break down
lactose (milk sugar)
