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Flashcards in Enzyme Kinetics Deck (40):
1

Factors (4) that affect enzyme kinetics

Temperature, pH, presence of activators/inhibitors, substrate

2

What effect does pH have on a protein?

pH affects protonation/deprotonation of an active site and can lead to denaturation in extremes.

3

What is the optimal temperature for enzyme activity?

37 degrees Celsius

4

As temperature increases by 10 degree increments toward 37 degrees Celsius, the enzyme's activity increases by ___.

2x

5

Why is transition state energy important for enzyme-substrate binding?

Transition state energy is used for the enzyme to complete its rxn

6

Why do enzymes have no effect on the Keq ([P]/[S])?

Enzymes are released at the end of the reaction. Enzymes "cancel out" at the end of the reaction.

7

In a zero order reaction, the substrate is ____ so the reaction is dependent on concentration of___.

saturated, enzyme

8

First order reactions are dependent on ____ concentration.

substrate

9

Second order reactions are often treated as ___-___ ___ reactions because the amount of one of the ____ is kept very high.

pseudo-first order, substrates
E.g. think of water being in high concentration. We ignore water when it is one of the substrates because the reaction becomes independent of water.

10

Which step in the Michaelis-Mentin model is the rate limiting step?

K2

11

Write out the Michaelis Menten Equation.

v= [vmax {S}]/[Km + {S}]

12

The Km value equals ___ in first order kinetics.

1/2 vmax

13

If you want to understand the enzyme activity, run the experiment at ___ ___ reaction conditions. If you want to understand the substrate activity, run the experiment at ___ ___ reaction conditions.

zero order, first order

14

What does the Km value mirror?

The substrate concentration.

15

The amount of substrate that yields product per molecule of enzyme available. Also called the turnover rate.

Kcat

16

Enzymes with a high K2/Km (or Kcat/Km) value are reaching ____ ____.

Kinetic perfection

17

Kcat/Km is also called the ___ ___.

Specificity constant

18

When comparing two enzymes, saturate with [S] and choose the enzyme with the highest what?

Specificity constant
Explanation: means that the enzyme binds to the substrate with high affinity and has a high turnover rate.

19

What does having an easily diffusible product (like carbon dioxide) do to the specificity constant?

Increases the value

20

What types of reactions form a ternary complex?

single displacement and random

21

How do single displacement reactions appear on a Lineweaver-Burk graph?

The lines intersect at vmax

22

How do double displacement reactions appear on a Lineweaver-Burk graph?

The lines are parallel

23

Double displacement reactions are also called ___ ___ reactions.

Ping Pong

24

What are the three types of reversible enzyme inhibitors?

Competitive, noncompetitive, uncompetitive

25

How to overcome competitive inhibition?

increase [S]

26

Competitive Inhibition (change or no change): Km__ and Vmax___.

No change for Km, change in Vmax

27

Where does the inhibitor bind in noncompetitive inhibition?

At a separate site than the substrate

28

Noncompetitive Inhibition (change or no change): Km__ and Vmax ___.

No change for Km, change in Vmax

29

What is a subcategory of noncompetitive inhibition?

Mixed inhibition

30

Mixed Inhibition (change or no change): Km___ and Vmax___.

Change in Km, no change in Vmax

31

What must happened before an uncompetitive inhibitor binds?

The enzyme and substrate are already bound

32

Uncompetitive Inhibition (change or no change): Km___ and Vmax___.

Km apparent change, vmax decrease

33

How does uncompetitive inhibition appear on a Lineweaver-Burk graph?

Parallel lines

34

1. What does Methotrexate compete against?
2. What process is shut down?
3. Which enzyme is inhibited?

1. folic acid
2. DNA synthesis
3. dihydrofolate reductase

35

Statins are competitive inhibitors for ___ _____ used in _____ synthesis.

HMG-CoA reductase, cholesterol synthesis

36

What is an example of irreversible inhibition in relation to bacteria?

Antibiotics
Explantation: drug covalently binds to Ser residue in transpeptidase which polymerizes peptidoglycan of gram (-) bacteria.

37

Arsenite is a noncompetitive inhibitor of what enzyme family?

Lipoamide DH
E.g. PDH, and alpha ketoglutarate DH

38

What enzyme stabilizes the transition state?

stickase

39

How do enzymes affect Keq?

Do not. Reaction reaches equilibrium faster only

40

What does a mixed inhibitor graph look like?

No intersection on axes. Change in both values