Enzyme Kinetics

Question 1

The velocity (v) of a simple reaction is measured by the disappearance of reactant (A) or by the appearance of product (P) per unit time, and is a function of the concentration of reactant. What is the equation for this?

Answer 1

v = d[P]/dt = -d[A]/dt = k[A]

Question 2

give the velocity equation for a zero order reaction

Answer 2

v= k

Question 3

give the velocity equation for a first order reaction

Answer 3

v = k[A]

Question 4

give the velocity equation for a second order reaction

Answer 4

v = k[A]^2

Question 5

What are the assumptions of the michaelis-menten equation?

Answer 5

1. use only initial velocities, then [P] = 0 and therefore k4 can be ignored
2. [ES] is constant, the “steady state” assumption

Question 6

What is the michaelis-menten equation?

Answer 6

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

Question 7

When does Vmax = K3 [Etotal]

Answer 7

When [S] is very high, the enzyme will be saturated with S such that [ES] = [Etotal]

Question 8

What does it mean in terms of saturation, for an enzyme to be at Vmax

Answer 8

since the enzyme is saturated with S, adding more S will not result in an increase in activity - this represents Vmax

Question 9

Km = ?

Answer 9

(k3 + k2) / k1

Question 10

At very low [S], the change in velocity with [S] approximates a linear response. This region is ____-____ order kinetics

Answer 10

pseudo-first

Question 11

At very high [S], the velocity approaches Vmax in an asymptotic fashion. This region represents ____-____ order kinetics (the v no longer varies with an increase in [S]

Answer 11

pseudo-zero

Question 12

The Km equals the [S] at which the velocity is what?

Answer 12

one-half maximum

Question 13

Enzymes with lower Km, are said to have a ___ affinity for their substrates than enzymes with a higher Km

Answer 13

greater

Question 14

A lower Km means a lower Km means a lower concentration of S is required to achieve what?

Answer 14

1/2 Vmax

Question 15

Since Km represents (k3 + k2) / k1, a low Km means ___ of ES is more rapid than the ___ of ES

S + E -> ES -> E + P

Answer 15

formation; breakdown

Question 16

In most cases, k3 is the ___ ____ step in catalysis, and therefore may be called kcat, or the turnover number

Answer 16

rate limiting

Question 17

If one knows the Vmax, and [Etotal], the value of kcat can be calculated and will be what?

Answer 17

the moles of product formed per mole of enzyme per unit time, at maximum velocity

Question 18

give the equation for the lineweaver-Burk plot

Answer 18

reciprocal of michaelis-menten

1/v = (Km/Vm)(1/S) + 1/Vm

Question 19

What is the slope of the line in a lineweaver-burk plot? Y intercept? X intercept?

Answer 19

(m) = Km/Vm ; 1/Vm; -1/Km