Enzymes Flashcards
What is a Cofactor of an enzyme?
Non-protein component of an enzyme needed for activity
What is a Coenzyme?
Complex organic molecule
What is a coenzyme produced from?
A vitamin
What is a prosthetic group?
A type of Cofactor covalently bound to the enzyme
What is an apoenzyme?
The protein component of an enzyme that contains a prosthetic group
What is Vmax?
Maximum rate achieved by the enzyme system
What is the Km?
The substrate concentration when reaction rate is half Vmax
What is the Vo?
Initial velocity of an enzyme reaction
What is the Michaelis Constant?
Km=k-1 + k2/k1
What does a large Km indicate?
A less stable ES complex (complex formed between enzyme and substrate)
What does a low Km indicate?
A more stable ES complex
What does the Michaelis Constant tell us?
The affinity of an enzyme for a substrate.
How does a competitive inhibitor bind to a substrate?
The same way the intended substrate does, at the active site. (Non-covalently)
What does competitive inhibition do to Vmax and Km?
Increases Km, Vmax can remain the same
How is Competitive inhibition overcome?
By increasing the concentration of the intended substrate
How does a non-competitive inhibitor bind to a substance?
Bind non-covalently to a site other than the active site
What does non-competitive inhibition do to Km and Vmax?
Km is unchanged (substrate can still bind to active site) but Vmax decreases as the inhibitor can’t be displaced.
The concerted and Sequential models are examples of what?
Allosteric enzymes
What kind of inhibition do allosteric enzymes produce?
Non-Competitive inhibition
Explain the concerted model
Sub units, in 2 different conformations (low Km and high Km)
Enzyme flips between conformations
When 1 substrate binds this causes the other units to hold an open conformation for more substrate, increasing affinity.
Explain the sequential model
No flipping between states
Binding to a substrate causes conformational change in 1 subunit
This causes a change in the next subunit which makes further binding easier
