Enzymes are catalysts:
- Catalysts are agents that increase the rate of chemical reactions.
- They reduce the activation energy.
- These reactions would happen anyway.
- Enzymes increase the rates millions of times.
- Enzymes are very specific for the substrate on which the act.
- Substrate is the specific molecule that the enzyme acts on.
- Physical conformation (shape) of enzyme is crucial.
- On the enzyme is the active site into which the substrate fits.
- The substrate fitting into the enzymes causes the enzyme to change its shape, an induced fit.
- This also induces stress on the substrate and allows for bonds to be broken easier.
Factors Affecting Enzyme Action
- Enzymes function within a narrow range of pH and temperature.
- May require nonprotein cofactors.
- Competitive inhibitors will block the active site.
- Noncompetitive inhibitors bind to enzyme and cause shape change. Examples: some pesticides and antibiotics.
- Some enzymes have allosteric sites. When an allosteric regulator binds to this site the entire conformation of the enzyme changes.
- Think of the enzyme cycle as a pathway.
- A metabolic end product can act as an inhibitor for an earlier enzyme path.