Chapter 6: Enzyme Kinetics

Question 1

What determines the rate of a chemical reaction?

Answer 1

• Concentration of reactants
• Temperature
• Activation Energy

Question 2

Define velocity in relation to Enzyme Kinetics

Answer 2

The quantity of reactant that disappears in a specified time

Question 3

How do you determine velocity in 0, 1st, and 2nd order reactions?

Answer 3

0 Order: v = k
1st Order: v = k[A]
2nd Order: v = k[A][B]

Question 4

Why do enzymatic reactions slow down as time passes?

Answer 4

• The substrate is being depleted or the reaction is reaching equilibrium
• The products are inhibitory to the enzyme leading to the loss of activity
• The enzyme denatures over time and loses activity

Question 5

What is the equation for [ES]?

Answer 5

[ES] = ([S][Et])/(Km+[S])

Question 6

What is the equation for initial velocity?

Answer 6

Vo = (Vmax*[S])/(Km+[S])

Question 7

Is Km intrinsic to a given enzyme? What about Vmax?

Answer 7

Km is intrinsic to a given enzyme but Vmax is not

Question 8

How can you find Vmax using the “turnover number”?

Answer 8

Vmax = Kcat*[Et]

Question 9

What is the equation for a Lineweaver-Burke Plot?

Answer 9

1/Vo = (Km/Vmax)*(1/[S]) + 1/Vmax

Question 10

What are the two types of enzyme inhibitors? Which kind is permanent?

Answer 10

Reversible Inhibitors (non-covalent)

Irreversible Inhibitors (Covalent) PERMANENT

Question 11

How do reversible and irreversible inhibitors interact with enzymes?

Answer 11

Irreversible Inhibitors REACT with enzymes and permanently shut them off. (often powerful toxins)

Reversible Inhibitors bind to and dissociate from the enzyme. (Often structural analogs of substrates or products)

Question 12

What are the kinds of Reversible Inhibitors?

Answer 12

Competitive Inhibitors

Non-competitive Inhibitors

Uncompetitive Inhibitors

Question 13

How do Competitive Inhibitors inhibit enzyme functionality? Does Vmax change? Km?

Answer 13

They compete with the substrate for the spot at the binding site. (With a LARGE quantity of Substrate you can still reach Vmax) Km increases

Question 14

What do Noncompetitive Inhibitors bind to? How is Vmax affected? Km?

Answer 14

The enzyme and the enzyme-substrate complex. Vmax is lowered, but Km is unaffected.

Question 15

What do Uncompetitive Inhibitors bind to? How is Vmax affected? Km?

Answer 15

They bind to the enzyme-substrate complex but not the free enzyme. Vmax is lowered and so is Km.