Chapter 5: 5.1 Kinetics

Question 1

Define:

Kinetics

Answer 1

The study of enzymatic reactions

Question 2

What does kinetics investigate?

Answer 2

Investigates the maximum rate of reaction as well as substrate and/or inhibitor specificity

Question 3

What do enzymes do?

Answer 3

Lowers the energy barrier a reaction must overcome

Question 4

True or False:

The enzyme contributes to the reaction

Answer 4

False, the enzyme does not contribute to the reaction (is in native state at the end of reaction)

Question 5

True or False:

Enzymes can alter the equilibrium of the reaction

Answer 5

False, enzymes do not alter the equilibrium of the reaction

Question 6

Define:

Rate of reaction (V)

Answer 6

The quantity of substrate that disappears in a unit of time

Question 7

Define:

Initial rate of reaction (V0)

Answer 7

Rate when substrate concentration is constant

Question 8

Define:

Maximum rate of reaction (Vmax)

Answer 8

Maximum rate of reaction when the enzyme is saturated by substrate

Question 9

State:

Formula for V0

Answer 9

V0 = Δ[S] / Δt

Question 10

Define:

Michaelis-Menten Equation

Answer 10

A way of expressing the relationship between initial velocity, maximum velocity, and initial substrate concentration

Question 11

State:

Michaelis-Menten Equation

Answer 11

V0 = Vmax * ([S] / (Km + [S]) ) = kcat * ( ([E] * [S]) / (Km + [S]) )

Question 12

Define:

Michaelis-Menten constant (Km)

Answer 12

The [S] at which V0 = 1/2 Vmax
* Indicates how [S] affects enzyme function

Question 13

State:

Michaelis-Menten constant (Km)

Answer 13

Km = (k2 + k-1) / k1

Question 14

State:

The relationship between efficiency of an enzyme and the Km value

Answer 14

The lower the Km value, the more efficient the enzyme is

Question 15

Define:

Turnover Number (kcat)

Answer 15

The maximum theoretical reaction rate for a single saturated enzyme

Question 16

If kcat = 9 s^-1, what does this mean?

Answer 16

Every 1 second, 1 enzyme can process 9 substrate molecules

Question 17

State:

Turnover Number (kcat)

Answer 17

kcat = Vmax / [E]

Question 18

State:

The relationship between power of the enzyme and the kcat value

Answer 18

The higher the kcat value, the more powerful the enzyme is

Question 19

Define:

Specificity Constant (kcat/Km)

Answer 19

The ratio of the turnover number and the Michaelis-Menten constant

Question 20

What is the Specificity Constant (kcat/Km) used for?

Answer 20

Used to compare enzymes
* The higher the ratio the more efficient and more powerful (overall better) the enzyme

Question 21

Define:

Lineweaver-Burke Plot

Answer 21

The double reciprocal of the Michaelis-Menten equation

Question 22

What does the Lineweaver-Burke Plot allow for?

Answer 22

Allows for a more precise identification of Vmax and Km

Question 23

State:

Lineweaver-Burke Plot equation

Answer 23

1/V0 = Km/Vmax * 1/[S] + 1/Vmax

Question 24

Define:

Inhibitors

Answer 24

Any molecule that binds to an enzyme and inhibits its function (slows the rate of reaction)

Question 25

# True or False: The stronger the inhibitor, the higher concentration needed to impact rate

Answer 25

False, the stronger the inhibitor the lower concentration needed to impact rate

Question 26

What are the types of inhibitors?

Answer 26

1. Reversible inhibition 2. Irreversible inhibition

Question 27

# Describe: Reversible inhibition

Answer 27

Reversibly inactivates enzymes * Inhibitor binds non-covalently to the enzyme

Question 28

What are the two methods of reversible inhibition?

Answer 28

1. Competitive inhibition 2. Non-competitive inhibition

Question 29

# Describe: How revesion occurs in competitive inhibition

Answer 29

Reversion occurs through increasing amount of substrate (out-competes for active site)

Question 30

# Describe: How reversion occurs in non-competitive inhibition

Answer 30

Effects are reversed by lowering inhibitor concentration

Question 31

# Describe: Irreversible inhibition

Answer 31

Inhibitor covalently binds to the active site of the enzyme

Question 32

# True or False: In irreversible inhibition, inhibitor closely resembles the substrate or a transition state

Answer 32

True

Question 33

# Describe: Competitive inhibition

Answer 33

Inhibitors which compete with the substrate for binding to the active site

Question 34

Competitive inhibition ------- the rate at which the enzyme binds the substrate

Answer 34

Reduces

Question 35

# In Competitive Inhibition of Enzymes: State what happens to: 1. Vmax 2. Km

Answer 35

If reversible, 1. Does not change Vmax 2. Increases Km

Question 36

# Describe: Non-competitive inhibition

Answer 36

Inhibitors binds to a site on the enzyme somewhere other than the active site

Question 37

# In Non-Competitive Inhibition of Enzymes: State what happens to: 1. Vmax 2. Km

Answer 37

1. Lower Vmax 2. Km is unchanged

Question 38

# For a competitive inhibitor: 1. Effect on Vmax 2. Effect on Km 3. How it is reversed

Answer 38

1. Vmax is **unchanged** 2. Km is **increased** 3. Reversed through **increasing** [**Substrate**]

Question 39

# For non-competitive inhibitor: 1. Effect on Vmax 2. Effect on Km 3. How it is reversed

Answer 39

1. Vmax is **decreased** 2. Km is **unchanged** 3. Reversed through **decreasing** [**Inhibitor**]

Question 40

How do the effects of irreversible inhibitors compare to reversible inhibitors?

Answer 40

Same as what is seen for Non-Competitive Reversible inhibitors

Question 41

How are effects for irreversible inhibitors diminished?

Answer 41

Diminished through decreasing the concentration of inhibitor