Enzymes II BI25M7-2015_

Question 1

What happens to V0 at low [S]?

Answer 1

There is an almost linear increase in V0 as [S] increases.

Question 2

What occurs at high [S] in enzyme kinetics?

Answer 2

V0 changes very little in response to increases in [S].

Question 3

What is Vmax?

Answer 3

Maximum reaction velocity.

Question 4

What does Km represent in enzyme kinetics?

Answer 4

The substrate concentration at which the initial reaction rate is half of the maximum reaction rate.

Question 5

What does the Michaelis-Menten equation express?

Answer 5

V0 = Vmax[S] / (Km + [S])

Question 6

How is Km defined using rate constants?

Answer 6

Km = (k-1 + k2) / k1

Question 7

What does a larger Km value indicate?

Answer 7

A less stable ES complex.

Question 8

What does a smaller Km value indicate?

Answer 8

A more stable ES complex.

Question 9

What does Vmax tell us about an enzyme?

Answer 9

How fast a reaction is proceeding when the enzyme is saturated with substrate.

Question 10

What is the effect of cell conditions on Km and Vmax?

Answer 10

The figures may change in response to cell conditions.

Question 11

What is the equation for V0 at low [S] in the M-M model?

Answer 11

V0 ≈ Vmax[S] / Km

Question 12

What is the equation for V0 at high [S] in the M-M model?

Answer 12

V0 ≈ Vmax

Question 13

What is steady-state kinetics?

Answer 13

Study of initial rates of reaction when [ES] is at steady state.

Question 14

What is a Lineweaver-Burk plot?

Answer 14

A graphical representation of the M-M equation rearranged to form a straight line.

Question 15

What is the significance of the shape of the V0 vs. [S] plot?

Answer 15

It shows the hyperbolic curve and levels off at Vmax.

Question 16

What type of enzymes do not follow M-M kinetics?

Answer 16

Allosteric enzymes.

Question 17

What is cooperative binding in enzymes?

Answer 17

One substrate binding to an enzyme subunit can influence other active sites.

Question 18

What is an example of a reaction without ternary complex formation?

Answer 18

Reactions where amino groups are shuttled between amino acids and ketoacids.

Question 19

What type of mechanism does creatine kinase exhibit?

Answer 19

Random sequential mechanism.

Question 20

What is the Cleland notation used for?

Answer 20

To represent reaction pathways involving substrates and products.

Question 21

What is a double displacement or ping-pong reaction pathway?

Answer 21

A reaction where substrates bounce on and off the enzyme as they are catalyzed.

Question 22

What is the relationship between glucokinase and hexokinase?

Answer 22

They are isozymes that catalyze the same reaction but have different kinetic properties.

Question 23

What is the role of glucokinase when blood glucose levels are high?

Answer 23

It increases activity to respond proportionally to blood glucose levels.

Question 24

How do you calculate Km from ES concentration?

Answer 24

Km = ([ETOTAL - ES][S]) / [ES]

Question 25

What is the significance of the steady state in enzyme kinetics?

Answer 25

It indicates that the concentration of the enzyme-substrate complex remains constant.

Question 26

What does the M-M equation account for?

Answer 26

The hyperbolic curve observed when plotting V0 against [S].

Question 27

Fill in the blank: Km is equivalent to the substrate concentration at which the initial reaction rate is ______.

Answer 27

half of the maximum reaction rate.

Question 28

True or False: Vmax can be effectively calculated from a graph that reaches a plateau.

Answer 28

False.

Question 29

What is the equation represented on the left?

Answer 29

[ES] K m + [ES][S] = [E] TOTAL [S] ## Footnote This equation involves terms related to energy and possibly a physical or mathematical context.

Question 30

What is the first step after establishing the left-hand terms?

Answer 30

Factor [ES] out of the left-hand terms ## Footnote This step simplifies the equation for further manipulation.

Question 31

What does the equation become after factoring [ES] out?

Answer 31

[ES] (K m + [S]) = [E] TOTAL [S] ## Footnote This indicates that the total energy is related to the sum of terms multiplied by [ES].

Question 32

What is the final operation performed on the equation?

Answer 32

Divide both sides by (K m + [S]) ## Footnote This step isolates [ES] for solving or further analysis.

Question 33

What does the divided equation express?

Answer 33

[ES] = [E] TOTAL [S] / (K m + [S]) ## Footnote This form is useful for determining the value of [ES] given total energy and other parameters.

Question 34

In the context of the equations, what do E, S, and K represent?

Answer 34

E = energy, S = another variable or state, K = constant or coefficient ## Footnote These variables are common in equations dealing with physical systems.

Question 35

True or False: The equation shows a relationship between energy and state variables.

Answer 35

True ## Footnote The relationship is fundamental in many physical equations.

Question 36

Fill in the blank: The equation can be simplified by factoring out _______.

Answer 36

[ES] ## Footnote Factoring is a common algebraic technique used to simplify expressions.