Chapter 7: Kinetics and Regulation

Question 1

Enzyme kinetics is the study of….

Answer 1

enzyme activity

Question 2

First order reactions

Answer 2

V = k [A]
+ the velocity (v) is the quantity of reactant [A] that disappears in a specified unit of time (t)
- units = S-1 (per sec)
- only one reactant
- how much A disappears, how much P appears

Question 3

Second Order reactions

Answer 3

A + B –> P Rate: V=k[A][B]
- bimolecular rxns
- many important rxns are 2nd order
+ Units = per mole per sec (M-1S-1)

Question 4

2nd- order rxns can appear to be 1st order rxns. T or F?

Answer 4

True - these are called Pseudo-first Order reactions!
- bimolecular rxn where the conc. of one reactant exceeds the concentration of 2nd reactant
+ rxn is first order in respect to A & will not depend on B

Question 5

Describe the graph for enzyme activity rates (V0)

Answer 5

• graphed as as initial velocity (V0) vs. amount of substrate
• V0 determined from initial slope of rxn rate vs. time
• Also determined from different substrate concentration then plotted

Question 6

Isoenzymes are ….

Answer 6

different enzymes who catalyze the same reaction
- different tissues
- different kinetics
- different regulation

Question 7

Sequential reactions

Answer 7

formation of a complex consisting of the two substrates and the enzyme

Question 8

What does Km refer to?

Answer 8

Michaelis Constant: describes enzyme substrate ‘affinity’ (affinity constant)

• Substrate concentration required for half-maximal activity

low Km = high infinity (tight bonding)
high Km = low affinity (loose bonding)

Typical values for Km are 10(-4)M to 10(-6) M

Question 9

Vmax

Answer 9

-describes substrate concentration when the enzyme is saturated (Michaelis)

-Maximum velocity
- velocity of reaction with plateau at a certain substrate concentration
- Increase substrate results in no further increases in velocity

Question 10

Michaelis-Menten Equation Vmax and Km

Answer 10

When : Vo = 1/2 Vmax
Then: Km =[S]
Thus. Km is the substrate concentration that yields 1/2 Vmax

Question 11

Double displacement

Answer 11

• formation of a substituted enzyme intermediate