Enzymes

Question 1

Name the X6 classes of enzymes, what they do and an example.

Answer 1

See folder for answer

Question 2

Explain the induced fit model.

Answer 2

The binding of a substrate to an enzyme induced a change in the enzymes active site to alter its shape to be more complementary to the substrate.

Question 3

What is the difference between co-enzymes and co-factors?

Answer 3

Co-enzymes are larger and organic

Co-factors are smaller and inorganic

Question 4

What is saturation kinetics?

Answer 4

The point past which further increases in substrate will have no effect on the rate of reaction as the enzyme is fully saturated

Question 5

What is the reaction rate order at low substrate concentrations?

Answer 5

First order

Question 6

What is the reaction rate order at high substrate concentrations?

Answer 6

Zero order

Question 7

What shape does a reaction rate vs substrate concentration graph usually take?

Answer 7

A rectangular hyperbola

Question 8

What is Vmax?

Answer 8

The maximum velocity of a reaction, when all the active sites are full

Question 9

What is Km?

What is its equation?

Answer 9

The Michaelis-menton constant

Km = (K-1 + k2) / k1

Question 10

What is the Michaelis-menton equation?

Answer 10

Vo = (Vmax x substrate conc.) / (km + substrate conc.)

Vo = initial reaction velocity

Question 11

What is the relationship between Km and the substrate concentration when Vo = 0.5max?

What, therefore, is Km?

Answer 11

Km = substrate conc.

Therefore Km = the substrate concentration at which the initial velocity is half the maximal velocity

Question 12

What does Kcat mean?

Answer 12

The turnover number

The number of substrate molecules an single enzyme can convert to product in a given unit of time, when the enzyme is saturated with substrate

Question 13

What is the best method for comparing X2 enzymes?

Answer 13

The specificity constant

Question 14

What is the specificity constant calculation?

Answer 14

Kcat / Km

Question 15

What is the equation for a line weaver Burke plot?

Answer 15

1/Vo = Km/Vmax (multiplied by) 1/substrate conc. + 1/Vmax

Question 16

What is the Y intercept of a lineweaver Burke plot?

Answer 16

1/Vmax

Question 17

What is the X intercept of a lineweaver Burke plot?

Answer 17

-1/Km

Question 18

What are the X5 combinations of the X4 monomers that make up LDH?

Answer 18

H4
H3M1
H2M2
H1M3
M4

Question 19

What effect on Km and Vmax does a competitive inhibitor have?

What will this do to the:

1) Reaction rate vs substrate conc. graph?
2) lineweaver Burke plot?

Answer 19

It will reduce the Km but not the Vmax

1) move the line right
2) make the line steeper by reducing the X intercept number, but have the same Y intercept

Question 20

What effect on Km and Vmax does a non-competitive inhibitor have?

What will this do to the:

1) Reaction rate vs substrate conc. graph?
2) lineweaver Burke plot?

Answer 20

It will alter the Vmax but not the Km

1) it will shift the graph Vmax down
2) it will have the same X intercept but a lower Y intercept, making the line less steep

Question 21

What is an allosteric molecule?

Answer 21

One that binds away from the active site to changes the active sites conformation and make it more or less active