More enzymes Flashcards
(19 cards)
What is the rate equation for a reversible reaction A ⇌ P?
v=k1[A]−k −1[P]
What does ΔG tell you about a chemical reaction?
ΔG indicates the spontaneity of a reaction. If ΔG < 0, the reaction is spontaneous.
What is the significance of standard free energy change (ΔG°)?
ΔG° is the free energy change under standard conditions (1 M concentration, 1 atm, 25°C).
What is the relationship between rate constant (k) and activation energy?
𝑘∝𝑒^−Δ𝐺‡/𝑅𝑇 ; a lower activation energy gives a higher rate constant.
Define molecularity.
The number of reactant molecules involved in an elementary step.
Define reaction order.
The power to which a reactant concentration is raised in the rate law.
What is kcat?
The turnover number; the number of substrate molecules converted to product per enzyme per second at saturation.
What is kcat/Km?
A measure of catalytic efficiency; higher values indicate more efficient enzymes.
When can Km be considered a measure of substrate affinity?
When k2 «_space;k-1 and kcat ≈ 0, i.e., ES complex formation is rapid and in equilibrium.
Difference between reversible and irreversible inhibition?
Reversible inhibition involves non-covalent interactions; irreversible inhibition involves covalent binding to the enzyme.
What is competitive inhibition?
The inhibitor binds to the active site, blocking substrate access.
Effect of competitive inhibition on Km and Vmax?
Increases Km, Vmax remains unchanged.
How does competitive inhibition affect a Michaelis-Menten plot?
The curve rises more slowly; Vmax is still reached at high [S].
How does competitive inhibition affect a Lineweaver-Burk plot?
Increases the slope and x-intercept (Km changes), y-intercept (1/Vmax) stays the same.
How does non-competitive inhibition affect Km and Vmax?
Km unchanged; Vmax decreases.
How does uncompetitive inhibition affect Km and Vmax?
Both Km and Vmax decrease.
What is a hallmark of irreversible inhibition?
Covalent modification of the enzyme that permanently inactivates it.
What is a suicide inhibitor?
A substrate analog that binds to the enzyme and irreversibly inactivates it during the normal catalytic process
What is the ‘active site’ of an enzyme?
The region where substrate binding and catalysis occur.
