Quiz 4 Flashcards
What is Km?
The substrate concentration needed to reach HALF max velocity. Also, it is an approximate measure of the affinity of the active site for the substrate.
What would be the effect of a mutation in an enzyme that decreases substrate binding, but not catalysis?
Increased Km, because more substrate is needed.
However, Vmax isn’t affected because it doesn’t interfere with catalysis.
Do enzymes cause forward reactions to be favored over backwards reactions?
No. Enzymes affect forward and reverse reactions equally.
Why do enzymes lower the activation energy for specific reactions?
To determine which chemical reactions occur in cells.
How do enzymes determine which chemical reactions occur in cells?
By lowering the activation energy of specific reactions.
When will all active sites be bound to substrate?
When the substrate concentration is much higher than Km.
Does substrate concentration determine the Km of an enzyme-catalyzed reaction?
No. The value of Km only deals with the substrate concentration of half velocity, and doesn’t deal with the substrate concentration PRESENT in the reaction.
What are the mechanism of catalysis?
Covalent bonding of the substrate with the enzyme AND weak non covalent bonds of the enzyme with the substrate.
How does an enzyme force the substrate into the transition state structure?
It uses the energy of binding.
A mutation doesn’t affect catalytic rate. How does this relate to Vmax?
It doesn’t affect Vmax.
What would be a case of increased Km, but not increased Vmax?
A mutation that occurs in an enzyme which causes Substrate concentration to decrease, but doesn’t affect catalysis.
