CH 7

Flashcards covering key concepts from Chapter 7 of Biochemistry: Kinetics and Regulation, focusing on reaction rates, Michaelis-Menten kinetics, and enzyme characteristics.

What is kinetics?

The study of reaction rates.

How is the velocity or rate of a reaction determined?

By measuring how much A disappears or how much P appears as a function of time.

What is the velocity called when [P] ≈ 0 in a simple reaction S→P?

Initial velocity (Vo).

How is initial velocity determined?

Measuring product formation as a function of time soon after the reaction has started.

What are the conditions for determining initial velocity?

Constant [E] and Vary [S].

Who derived the equation to describe initial reaction velocity as a function of substrate concentration?

Leonor Michaelis and Maud Menten.

According to Michaelis-Menten kinetics, what is KM equal to?

[S] at Vmax/2.

What does KM stand for?

The Michaelis Constant.

What is the equation for KM?

(k2 + k-1)/k1

What is KM a measure of?

An inverse measure of the affinity of the enzyme for its substrate.

What does a higher KM mean in terms of enzyme-substrate affinity?

Lower affinity.

What will an enzyme with a higher KM require to reach Vmax?

More substrate.

What are the symptoms caused by excessive amounts of acetaldehyde in the blood after alcohol consumption?

Facial flushing and rapid heartbeat.

What are the two different aldehyde dehydrogenases in most people?

A low KM and a high KM enzyme.

Which aldehyde dehydrogenase is inactivated in susceptible individuals, leading to acetaldehyde in the blood?

The low KM enzyme.

What is the name of the double-reciprocal equation?

Lineweaver-Burk equation.

In a Lineweaver-Burk plot, what does the x-intercept represent?

-1/KM

In a Lineweaver-Burk plot, what does the slope represent?

KM/Vmax

In a Lineweaver-Burk plot, what does the y-intercept represent?

1/Vmax

What does evidence suggest about the KM value in relation to substrate concentration?

The concentration of the substrate found in vivo.

If the enzyme concentration, [E]T, is known, what can Vmax be used to calculate?

Turnover number (kcat).

What is kcat?

The number of substrate molecules converted into product per second by a single enzyme molecule.

kcat/KM is a measure of what?

Catalytic efficiency.

What two factors does catalytic efficiency take into account?

The rate of catalysis (kcat) and the nature of the enzyme substrate interaction (KM).

What is the maximum possible catalytic efficiency limited by?

The rate at which enzyme and substrate diffuse together (≈108–109 s−1 M−1).