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Biomedical Lab > Lab 5 > Flashcards

Lab 5 Flashcards

1
Q

The rate of an enzymatic reaction is dependent both on ___ and ____

A

concentration of the reactants and concentration of the number of enzyme molecules available

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2
Q

The enzyme is a ____. It is not _____

A

catalyst. It is not destroyed.

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3
Q

When is the rate of the enzyme first measured?

A

as soon as the substrate and enzyme are mixed for a specified time

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4
Q

The kinetic properties of an enzyme are studied by determining the ______

A

initial velocity

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5
Q

At the initial velocity, what can you say about:
1. The concentration of the product
2. The backward reaction

A
  1. The concentration of the product is very small
  2. The back reaction
    es<—-p
    can be ignored
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6
Q

What are enzyme inhibitors?

A

molecules that inhibit enzyme activity

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7
Q

How do enzyme inhibitors work?

A

Bind to the enzyme and diminish the velocity of the enzymatic reaction

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8
Q

How are enzyme inhibitors classified?

A

the type of inhibition

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9
Q

What are irreversible inhibitors?

A

Irreversibly bind to and inhibit the enzyme. COVALENTLY bound and do not dissociate

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10
Q

What are reversible inhibitors?

A

Inactivates an enzyme through non covalent, more easily reversed, reactions.

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11
Q

What is Ki?

A

reversible inhibitor binding constant

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12
Q

How are reversible inhibitors classified?

A

By their enzyme kinetics

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13
Q

What are the 3 types of reversible inhibitors?

A
  1. Competitive Inhibitor
  2. Noncompetitive inhibitor
  3. Uncompetitive inhibitor
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14
Q

What is a competitive inhibitor?

A

Binds to the ACTIVE SITE to which the substrate binds and prevents substrate binding

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15
Q

How is a competitive inhibitor reversed?

A

By increasing the substrate

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16
Q

What is a noncompetitive inhibitor?

A

Binds to free enzyme or enzyme complex and prevents enzyme activity

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17
Q

What can you say about reversing a noncompetitive inhibitor?

A

independent of substrate concentration

18
Q

What is an uncompetitive inhibitor?

A

Binds only to ES complex. Prevents release of S and production of P

19
Q

When does enzyme inactivation occur?

A

When pH and temperature denature enzymes, and enzyme structure is changed

20
Q

The order of an enzymatic reaction is related to….

A
  1. The number of molecular species
  2. The rate of the reaction
21
Q

For a first order enzymatic reaction….

A

The enzyme concentration is maintained constant. Thus, the enzyme activity is solely dependent on the substrate concentration

22
Q

When the substrate is much LESS than the Km, the reaction is….

A

first order with respect to substrate, as the rate is proportional to a single reactant (substrate)

23
Q

When the substrate is much GREATER than the Km, the reaction is….

A

zero order with respect to substrate. Velocity is independent of substrate concentration

24
Q

Initial velocity (V0) is measured when…

A

the substrate is much greater than the concentration of the enzyme

25
Q

Initial velocity is measured using….

A

a constant concentration of enzyme

26
Q

At a relatively low concentration of substrate, the initial velocity is….

A

highly dependent on substrate concentration

27
Q

As the substrate concentration increases, what happens to initial velocity?

A

increases linearly and rapidly (more enzyme binds to substrate)

28
Q

What happens when enzymes are increasingly saturated with substrate?

A

initial velocity changes more slowly

29
Q

At Vmax, what happens when more substrate is added?

A

NOTHING - all enzymes are already saturated with substrate. Initial velocity remains constant

30
Q

When a reaction continues at the maximum initial velocity, what is reached?

A

a STEADY STATE

31
Q

An enzyme-catalyzed reaction can roughly be divided into 3 stages:

A
  1. enzyme-substrate binding
  2. Catalysis
  3. Product release
32
Q

Michaelis-Menten plot is __vs___

A

initial velocity vs substrate concentration

33
Q

The michaelis-Menten plot says that the velocity of an enzymatic reaction is greatest when…

A

all enzyme’s catalytic sites are filled with substrate

34
Q

Michaelis-Menten sonstant (km) describes the affinity of….

A

the substrate to an enzyme

35
Q

What is km?

A

the concentration of the substrate that will produce half the vmax

36
Q

Standard curve shows the relationship between…

A

absorbance and concentration

37
Q

The “trend line” of a standard curve is used to….

A

calculate unknown concentrations

38
Q

What enzyme is used to catalyze the hydrolysis of p-Nitrophenyl phosphate to p-nitrophenol?

A

acid phosphatase

39
Q

In terms of structure, what does acid phosphatase do to p-Nitrophenyl phosphate?

A

removes the phosphate group and replaces with OH

40
Q

p-nitrophenol absorbs maximally at…

A

405nm

41
Q

Highkm = ___ affinity

A

low

Biomedical Lab (10 decks)

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