W26 L1 - Enzymes - Michaelis Menten Equation

Flashcards covering the Michaelis Menten equation, Vmax, Km, and enzyme kinetics.

Describe the enzymatic reaction

Enzyme plus substrate binding in a reversible reaction to the active site, which turns the substrate into a product, releasing the free enzyme.

What are the rate constants in enzyme kinetics?

k1 (rate constant), k-1 (reverse rate constant), and k2 or kcat.

Why must the reaction be irreversible for the Michaelis-Menten equation?

The reaction must be irreversible to apply the Michaelis-Menten equation as it assumes the reaction proceeds only in the forward direction and the reverse reaction is negligible

• more straightforward analysis of enzyme kinetics

What condition is required regarding the product for the Michaelis-Menten equation to hold true?

No product must be present at the start/beginning of the reaction.

What is the initial rate in enzyme kinetics?

The rate measured right at the start of the reaction when no product has been formed yet.

What is the relationship between enzyme and substrate concentration for the Michaelis-Menten equation?

The enzyme concentration must be much smaller than the substrate concentration.

What is the Michaelis-Menten equation?

Rate (initial rate) = Vmax * [S] / (Km + [S])

Can linear regression be used on a rate vs. substrate concentration saturation curve?

No, because the relationship is not linear; it's a saturation curve.

What happens to the rate when the substrate concentration is much larger than Km?

V = Vmax

What is Vmax?

The maximum speed or rate at which an enzyme can work.

When is Vmax reached?

When all the active sites of the enzyme have substrate bound.

What does Vmax tell us about enzyme behavior?

An enzyme parameter that indicates how the enzyme works when the substrate concentration is extremely high.

What parameter tells us how the enzyme behaves at very low substrate concentrations?

Vmax / Km

What does Vmax/Km represent graphically?

The gradient at the beginning of the reaction on a rate vs. substrate concentration graph.

What happens to the rate when Km equals the substrate concentration?

V = 1/2 Vmax

What is Km (Michaelis constant)?

The substrate concentration that gives half of Vmax.

What does Km indicate about the enzyme-substrate interaction?

It is a measure of how much the enzyme likes the substrate (affinity); high Km means low affinity, and low Km means high affinity.

What is the unit for Vmax?

Concentration per time (e.g., micromolar per minute).

What is the unit for Km?

The same as the unit for substrate concentration (e.g., millimolar).

How can Vmax and Km be determined from a Michaelis-Menten plot?

It is the point where the graph plateaus. You can take half of Vmax to find the corresponding substrate concentration which equals Km.