Enzyme Kinetics Flashcards

1
Q

Factors (4) that affect enzyme kinetics

A

Temperature, pH, presence of activators/inhibitors, substrate

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2
Q

What effect does pH have on a protein?

A

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

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3
Q

What is the optimal temperature for enzyme activity?

A

37 degrees Celsius

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4
Q

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

A

2x

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5
Q

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

A

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

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6
Q

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

A

Enzymes are released at the end of the reaction. Enzymes “cancel out” at the end of the reaction.

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7
Q

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

A

saturated, enzyme

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8
Q

First order reactions are dependent on ____ concentration.

A

substrate

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9
Q

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

A

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.

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10
Q

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

A

K2

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11
Q

Write out the Michaelis Menten Equation.

A

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

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12
Q

The Km value equals ___ in first order kinetics.

A

1/2 vmax

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13
Q

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.

A

zero order, first order

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14
Q

What does the Km value mirror?

A

The substrate concentration.

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15
Q

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

A

Kcat

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16
Q

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

A

Kinetic perfection

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17
Q

Kcat/Km is also called the ___ ___.

A

Specificity constant

18
Q

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

A

Specificity constant

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

19
Q

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

A

Increases the value

20
Q

What types of reactions form a ternary complex?

A

single displacement and random

21
Q

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

A

The lines intersect at vmax

22
Q

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

A

The lines are parallel

23
Q

Double displacement reactions are also called ___ ___ reactions.

A

Ping Pong

24
Q

What are the three types of reversible enzyme inhibitors?

A

Competitive, noncompetitive, uncompetitive

25
Q

How to overcome competitive inhibition?

A

increase [S]

26
Q

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

A

No change for Km, change in Vmax

27
Q

Where does the inhibitor bind in noncompetitive inhibition?

A

At a separate site than the substrate

28
Q

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

A

No change for Km, change in Vmax

29
Q

What is a subcategory of noncompetitive inhibition?

A

Mixed inhibition

30
Q

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

A

Change in Km, no change in Vmax

31
Q

What must happened before an uncompetitive inhibitor binds?

A

The enzyme and substrate are already bound

32
Q

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

A

Km apparent change, vmax decrease

33
Q

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

A

Parallel lines

34
Q
  1. What does Methotrexate compete against?
  2. What process is shut down?
  3. Which enzyme is inhibited?
A
  1. folic acid
  2. DNA synthesis
  3. dihydrofolate reductase
35
Q

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

A

HMG-CoA reductase, cholesterol synthesis

36
Q

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

A

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

37
Q

Arsenite is a noncompetitive inhibitor of what enzyme family?

A

Lipoamide DH

E.g. PDH, and alpha ketoglutarate DH

38
Q

What enzyme stabilizes the transition state?

A

stickase

39
Q

How do enzymes affect Keq?

A

Do not. Reaction reaches equilibrium faster only

40
Q

What does a mixed inhibitor graph look like?

A

No intersection on axes. Change in both values