Catalysts and Enzymes
Notes
Chemical Reactions
• Reactants  Products
• Change the bonds found in the reactants to make
a product.
Catalysts…
• …Increase the rate of a reaction by
decreasing the activation energy.
•Activation Energy = Energy needed
to make or break bonds.
Reactions occur faster if it takes
less energy.
Enzymes and Catalysts…
– Lower the activation energy for chemical reactions
(a) Without enzyme
Enzyme
Activation energy
barrier
(b) With enzyme
Reactants
Products
Enzymes vs. Catalysts
• Enzymes are a type of catalyst.
Catalysts
Enzymes
Enzymes
Catalysts
• Proteins
• Not proteins
•Organic
•Inorganic
•Found in living
organisms
•Not made by
living organisms
•Most end in
-ase
•Don’t end in
-ase
•Specific
•Not specific
More Enzyme Characteristics
•Enzyme Reactions are reversible.
•Enzymes are reusable
•Enzymes do not change in a reaction
Key Terms
• Substrates = what enzymes act upon.
– (The Reactants of the chemical reaction)
•Active Site = site on the enzyme where
the substrates attach.
-- shape is specific to certain substrates
Key Terms
• Enzyme-Substrate Complex- When the
two are temporarily connected. Allows
bonds to be made or broken between the
substrates.
Key Terms
• Products:
– What is produced from the chemical reaction
Lock and key model of Enzyme Activity
Enzyme/Substrate Complex
Induced Fit
– The active site fits to the substrate, and the
enzyme changes shape slightly
– Like a hand shake
Affects of Temperature
• Heat denatures enzymes
•Denature = change the shape
R
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f
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a
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30o
40o
Temp oC
50o
Affects of pH
• Enzymes work best at certain pH’s
Cofactors and Coenzymes
• Both help the function of enzymes
•Both are NOT Proteins!
• Coenzymes:
•Cofactors:
•Organic
•Inorganic
•Vitamins
•Minerals
•ie) E
•ie) zinc
Coenzymes
Cofactors
Inhibitors
• Stop or inhibit enzyme activity
•3 types:
•Competitive
•Non-competitive
•feedback
Competitive Inhibitors
• Blocks the normal substrate from attaching
to the active site.
•ie) penicillin
Competitive Inhibitors
Substrate
Inhibitor
Enzyme
Enzyme
Substrate
Non-Competitive Inhibitors
• Bind to another part of the enzyme other
than the active site. This causes the
enzyme to change shape…rendering the
active site useless.
•ie) lead, mercury, fluoride
Non-competitive Inhibitors
Substrate
Inhibitor
Feedback Inhibitors
• The end product blocks the active site to
switch off a metabolic pathway
Why are enzymes important?
• Digestion: Help to break down food
•Energy: Help reactions in the mitochondria
that produce energy
•Synthesis: Help make molecules
•Allow reactions to occur (faster)