Biochemistry 5

Question 1

Describe the relationship between time and product:

Answer 1

Rate at which product accumulates with time is proportionate to the substrate concentration.

Question 2

What are the Michaelis Menton model equation?

Answer 2

E + S ⇌ ES –> E + P

km = [E][S]
——
[ES]

Vo = Vmax [S]
————
Km + [S]

Question 3

What is the Michaelis Menton model used for?

Answer 3

Predict the behaviour of an enzyme as we vary the substrate concentration and measure its enzyme activity

Question 4

What does this equation describe

Vo = Vmax [S]
————
Km + [S]

Answer 4

This equation describes the observed
effect of substrate on enzyme activity
where there is one substrate at
concentrations similar to Km

Question 5

What is the significance of Km?

Answer 5

Km values vary widely, is affected by the reaction environment and nature of the substrate
Km is the concentration of the substrate where (ES) = (E0)/2
Km is a measure of the affinity of a substrate for an enzyme

Question 6

On the Linewaever Burk plot graph what goes on the x and y axis

Answer 6

X axis - 1/ (S)
Y axis - 1/Vo

Question 7

What is the significance of Vmax ?

Answer 7

Corresponds to the rate of reaction when all enzyme binding sites are filled with substrate
Maximum turnover = maximum number of product molecules produced per unit time per active site
Most enzymes have one active site per polypeptide chain so Kcat = K2

Question 8

What is Kcat ?

Answer 8

Catalytic rate constant for the enzyme when fully saturated with substrate.

Question 9

What is the maximum turnover equation?

Answer 9

Vmax = k2 [Eo] = kCAT [E]T

Question 10

What can the Km/ Kcat ratio tell us?

Answer 10

About enzyme substrate specificity