How do enzymes affect the rate of reaction?

They lower the activation energy, so the rate of reaction increases.

What is the major difference between enzyme catalyzed and uncatalyzed reactions?

Catalyzed reactions tend to become saturated

1. What does reaction order mean?

2. Define:

1st order reactions

2nd order reactons

1. Reaction order referes to the number of molecules needed to interact

1st order= only 1 molecule

2nd order = 2 molecules or 2 of the same molecules

What does a substrate do to an enzyme?

Binds to it through conformational changes in the enzyme (referred to as induced fit model)

1. What is Vmax?

2. Why do you hit Vmax?

1. Vmax = the maximum theoretical velocity of a reaction

2. You hit Vmax because there is a finite number of enzyme particles

Define:

Km

Km = Michaelis constant

Km is the [S] where the velocity is half the Vmax

How does Km relate to affinity?

1. Low Km = high affinity

2. High Km= low affinity

1. When is V directly proportional to [S]?

2. Where would you see 1st and zero order reaction?

1. V is directly proportional to [S] at low [S]

2. 1st order occurs initially, and zero order is found at Vmax

Main difference between equilibrium and steady state

Equilibrium = [S] and [P] are independent of enzyme activity

Steady State = [S] and [P] depend on enzyme activity/degradation

What is the steady state assumption?

Enzyme-substrate complex does not change over time.  (K2 is equal to K-1)

Define:

Micahelis-Menten Equation

Vo = Vmax[S]/Km+ [S]

What is:

Kcat?

Kcat is the catalytic constant (turnover rate).  This is how much product is made per enzyme per second.

What is Kcat/Km?

The measure of catalytic efficiency.  Catalytic perfection is achieved at 10^8-10^9