Enzyme Kinetics

Question 1

What does Vmax represent

Answer 1

the max velocity of an enzyme substrate reaction

Question 2

What does Km represent

Answer 2

The Michaelis constant, which is the substrate conc. at half Vmax.

Question 3

What are the axes on a line weaver and burk plot

Answer 3

y axis = 1/v

x axis = 1/[s]

Question 4

What does the y intercept and extrapolation to x-axis represent on a line weaver and burk plot

Answer 4

• Intercept on y-axis is 1/Vmax

* Extrapolation to x-axis give intercept -1/Km

Question 5

What happens to the line weaver and burk plot with increasing enzyme concentration

Answer 5

– Reduces slope

– Increases Vmax

Question 6

What does a small and high Km mean

Answer 6

• Small Km means tight binding; high Km means weak

binding

Question 7

What are the 2 enzymes involved in glucose phosphorylation and which has the higher Km

Answer 7

Hexokinase = low Km compared to resting glucose conc
Glucokinase = high relative Km

Question 8

When does glucokinase phoshphorylate glucose and what glucose conc. will cause glucose to be excreted in the urine

Answer 8

glucokinase only phosphorylates glucose at high conc.

glucose conc above glucokinase Km will be pissed out (10mM)

Question 9

Does pepsin and trypsin work best at acidic, neutral or alkali conditions

Answer 9

pepsin - acidic

trypsin = a bit alkali