Enzymes Flashcards
What is the function of enzymes?
Do not alter the equilibrium yet speed up the time that equilibrium is reached at.
Name the 2 enzyme mechanisms.
Induced fit.
Lock and key.
Explain the lock and key mechanism.
The active site is complementary to the substrate.
Each active site is shaped to hold a specific substrate.
Explain the induced fit mechanism.
The active site and the substrate don’t fit perfectly.
Once the substrate binds the active site shape alters and becomes complementary.
Most enzymes are what?
Proteins
What is the exception to most enzymes being proteins?
Ribozymes (catalytic RNA molecules)
Define free energy change.
The difference in energy from the reactants at the initial stage and the products at the final stage.
Define activation energy.
Amount of energy required to activate a reaction.
Define thermodynamic activation.
Increase in free energy.
Define thermodynamic inactivation.
When proteins become denatured.
Define Vmax.
Maximum reaction rate. Where all enzymes are saturated with substrate.
Define Km.
The concentration of substrate where the reaction rate is half its maximum.
Vmax divided 2 = Km.
Km is the …
Inverse measurement of affinity
Describe a low Km.
Enzyme is fully saturated with substrate. Happens quickly.
Remains at a fairly constant rate.
Lower the Km, higher the affinity for the substrate.
Describe a high Km.
Enzyme not fully saturated, relies on the concentration of he substrate.
Activity varies.
What is a competitive inhibitor?
A molecule that is structurally similar to the substrate and competes with it for the active site.
How do competitive inhibitors affect Km and Vmax?
Vmax: Unaltered
Km: Lowered
How can the effects of completive inhibitors be reversed?
Increasing the concentration of substrate.
What is a non-competitive inhibitor?
A molecule that binds to an allosteric site on the enzyme,
How do non-competitive inhibitors affect Km and Vmax?
Km: Unaltered.
Vmax: Decreased.
What happens when modulators bind to enzymes?
Conformation changes occur.
What is the effect of a positive modulator?
Increases the affinity for the active site. (Negative has the reversed effect)
