Enzymes & Catalysis
What molecule does an enzyme bind and convert into product?
The substrate
What does Vmax represent in enzyme kinetics?
The maximum reaction rate of an enzyme-catalyzed reaction.
What type of inhibitor competes directly with the substrate for the enzyme’s active site?
A competitive inhibitor.
What molecule is the primary carrier of high-energy phosphate groups in cells?
ATP
What is oxidation?
Loss of electrons
What energy barrier do enzymes lower to speed up chemical reactions?
Activation energy
What is Km?
The substrate concentration at which the reaction rate is half of Vmax.
What type of inhibitor binds to an enzyme at a site other than the active site?
A noncompetitive inhibitor.
Which energy carrier primarily supplies high-energy electrons for biosynthesis?
NADPH
What is reduction?
Gain of electrons
What aspect of a reaction do enzymes NOT change, even though they increase reaction rate?
The equilibrium point.
What does a low Km indicate about an enzyme?
High affinity for its substrate.
Which type of inhibition increases Km but does not change Vmax?
Competitive inhibition.
Which carrier is most commonly associated with energy extraction during metabolism?
NADH
How does a competitive inhibitor impact the Km and Vmax?
does not change the Vmax, but shifts the Km to the right
Enzymes lower the activation energy of both the forward and reverse reactions by how much? (same or which one more?)
By the same amount.
Why does increasing substrate concentration eventually stop increasing reaction rate?
The enzyme has reached Vmax.
Which type of inhibition decreases Vmax but does not change Km?
Noncompetitive inhibition.
In what form do activated carrier molecules store energy?
As transferable chemical groups or high-energy electrons.
How does a non competitive inhibitor impact the Vmax and Km of a graph?
Vmax decreases, Km does not change
Why do cells break down glucose through many enzyme-catalyzed steps instead of one large reaction?
To capture energy for chemical work rather than losing it as heat.
Two enzymes have the same Vmax, but enzyme A has a lower Km than enzyme B. Under what condition will enzyme A reach a higher reaction rate?
At lower substrate concentrations.
Which type of inhibition can be overcome by increasing substrate concentration?
Competitive inhibition.
ATP hydrolysis is most often coupled to what type of reaction in biosynthesis?
Condensation reactions
Explain both competitive and noncompetitive inhibition.
Competitive: competes with substrate for binding to the enzyme active site
Noncompetitive: binds enzyme (not active site) to inhibit the enzyme activity and changes the active site.