Biochemistry I MCAT Lesson 3: Enzyme Kinetics

Questions and Answers

What is the rate law for the reaction A + B -> AB?

Rate = k [A] + [B]

Rate = k [A] - [B]

Rate = k [A][B]²

Rate = k [A][B] (correct)

In Michaelis-Menten kinetics experiments, which of the following is assumed to be true?

Substrate concentration is constant.

Increasing enzyme concentration will not change Vmax.

Enzymes are saturated at Vmax. (correct)

All of the above.

What can be assumed about reaction conditions in Michaelis-Menten kinetics experiments?

Constants ([E] and k) are not changing during the experiment.

Substrate can be converted into product without the enzyme.

Our solutions are behaving ideally.

Both A and B. (correct)

How can the rate of a reaction be increased assuming the rate constant (k) is constant?

Increase enzyme concentration. Signup and view all the answers

Adding more catalyst after a catalytic amount has already been added will increase the rate of reaction.

False Signup and view all the answers

What does it mean if the rate of reaction has reached maximum velocity (Vmax)?

The enzymes no longer have available active sites. Signup and view all the answers

If a reaction has reached Vmax, what would happen to the rate of reaction if we increase the substrate concentration?

It would remain the same. Signup and view all the answers

What is one way to increase the Vmax of a reaction?

Increase enzyme concentration. Signup and view all the answers

What are the respective reaction rate formulas for the enzyme catalysis steps E + S => ES => E + P?

Rate1 = k1 [E][S], Rate2 = k2 [ES] Signup and view all the answers

What is the steady-state assumption when talking about enzyme kinetics?

[ES] is constant. Signup and view all the answers

Study Notes

Enzyme Kinetics Overview

Enzyme kinetics studies the rates of enzyme-catalyzed reactions and factors influencing these rates.
Key parameters include substrate and enzyme concentrations, rate constants, and Vmax.

Rate Law Equation

For the reaction A + B → AB, the rate law is expressed as Rate = k [A][B].
Rate (change in concentration per unit time) depends on reactant concentrations and the rate constant (k).

Michaelis-Menten Kinetics Assumptions

Constant substrate concentration and saturation of enzymes at Vmax are key assumptions.
Increasing enzyme concentration will elevate Vmax; however, at Vmax, enzymes are saturated.

Ideal Behavior and Constant Factors

Solutions are assumed to behave ideally, and constants ([E] and k) are stable throughout the experiment.
Enzymes are essential for substrate conversion to product.

Reaction Rate Enhancement

Reaction rates can be increased by raising substrate or enzyme concentrations.
Adding inhibitors, regardless of type, does not enhance the reaction rate.

Catalyst Usage

A catalyst performs its function with a small amount known as a "catalytic amount"—adding more will not further influence the reaction rate.

Vmax and Active Sites

Vmax indicates saturation of enzymes; no increase in reaction rate occurs when substrate concentration rises because active sites are occupied.
To increase Vmax, one must raise the enzyme concentration.

Enzyme Catalysis Steps

Enzyme catalysis involves two key steps: formation of the enzyme-substrate complex (E + S → ES) and conversion to product (ES → E + P).
The respective reaction rates for these steps are: Rate1 = k1 [E][S] for the first step and Rate2 = k2 [ES] for the second step.

Steady-State Assumption

The steady-state assumption in enzyme kinetics posits that the concentration of the enzyme-substrate complex ([ES]) remains constant throughout the reaction.

Description

Test your knowledge on enzyme kinetics with this flashcard quiz from Biochemistry I Module of the MCAT Self Prep eCourse. Review key concepts such as rate laws and the factors affecting enzyme activity to prepare for your exam.