Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Molecules to Cells > Enzymes pt. 2 and 3 > Flashcards

Enzymes pt. 2 and 3 Flashcards

You may prefer our related Brainscape-certified flashcards:
Organic Chemistry 101 flashcards
1
Q

What is the reaction rate of a unimolecular irreversible first order reaction?

A -> P

A

v = k[A]

Thus the rate of P formation is directly proportional (rate constant k) to the concentration of A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What makes a reaction ‘first order’?

A

An exponent of 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the reaction rate of a bimolecular irreversible second order reaction?

A + B ->

A

Rate of P formation is directly proportional (rate constant k) to the concentration of reactants

v = k[A][B]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the unit of the rate constant for a first order reaction?

A

s-1

reciprocal second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the unit of the rate constant for a second order reaction?

A

M-1 s-1

reciprocal molarity, reciprocal second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the rate of formation for a unimolecular reversible reaction?

A -> P k1 and P -> A k2

A

Rate of formation of P equals rate of P gain minus rate of P gain

v = k1[A] - k2[P]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Keq = ?

A

k1/k2 = [P]/[A]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does a large Keq indicate?

A

Reaction favors products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does a small Keq indicate?

A

Reaction favors reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the basic michaelis-menten equation?

A

E + S -> ES > E + P

and the reverse for rxn 1

ES = enzyme substrate complex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the units of the Michaelis constant?

A

M

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What assumptions are made to simplify Michaelis-Menten?

A

[S]&raquo_space;> [E]

and [ES] is relatively unchanging

No back reaction from pdt build up (k4 = 0)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Maximal velocity (rate of rxn) occurs when __________.

A

Enzyme is totally saturated with enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Vmax = ?

A

= k3[E]total

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the Michaelis-Menten equation?

A

Vo = Vm[S] / Km + [S]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is Michaelis-Menten plotting?

A

Vo (rate) versus [S]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Km = ?

A

[S] at 1/2 Vmax

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Filled sites = ?

A

Vo/Vm = [S] / Km+[S]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is Km indicative of?

A

Enzyme-substrate affinity (higher Km, lower affinity)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

In the special condition of k2&raquo_space;> k3, what does that mean?

A

Making the product is the slowest reaction

Km = Kd ~ [E][S]/[ES]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

A low Km means what?

A

High binding affinity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

A high Km means what?

A

Low binding affinity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

To judge affinity, what must be true?

A

k2 must be much greater than k3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Increasing your enzyme concentration will ________ your maximum velocity (reaction rate)

A

Increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Turnover number = ? = ?

A

= k3 = kcat

“Catalytic ability” Typically 1-10^4

Higher value = higher catalytic ability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is catalytic ability?

A

Number of S molecules converted to P by one E molecule in unit time under saturation conditions

(the best your enzyme can be functioning)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What does kcat / Km indicate?

A

The catalytic efficiency of how well an enzyme reacts with dilute amount of substrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What type of enzymes have the higher kcat / Km values?

A

“Perfect” enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the equation of a Lineweaver-Burk plot?

A

1/Vo = ( Km/Vm * 1/[S] ) + 1/Vm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the slope of a lineweaver-burk plot?

A

Km/Vm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

The value of the slope in a lineweaver-burk plot is ______ proportional to the catalytic efficiency.

A

Inversely

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the y intercept of a lineweaver-burk plot?

A

1/Vm

33
Q

What is the x intercept of a lineweaver-burk plot?

A

-1/Km

34
Q

What is the advantage of lineweaber-burk?

A

Provides easy-to-interpret visual display

35
Q

What is the disadvantage of lineweaver-burk?

A

Distorts errors at low [S], compresses data at high [S]

36
Q

What are the two main classes of two-substrate (or bi-substrate) reactions?

A

Sequential (ternary)

Ping-pong (double-displacement)

37
Q

What is a sequential two substrate reaction? What are the kinds?

A

All substrates bind (ternary complex) before any product releases

Essentially, both come down before both come off.

Can be ordered (specific) or Random order

38
Q

What is a ping-pong or double replacement mechanism?

A

For two-substrate reactions, this describe when one substrate binds and released product before the second substrate binds and releases product.

39
Q

What enzyme is a classic ping pong enzyme?

A

Chymotrypsin - peptide bonds and releases product before water binds and releases water

40
Q

What is an enzyme inhibitor?

A

A small molecule or ion that binds an enzyme and decreases its activity.

41
Q

What are the two types of inhibitors?

A
  1. Reversible inhibitors

2. Irreversible inhibitors

42
Q

What are the features of reversible inhibitors?

A

Bind the enzyme with noncovalent interactions
Dissociate rapidly
Allow the enzyme to recover its original activity

43
Q

What are the features of irreversible inhibitors?

A

Bind the enzyme with covalent interactions

Result in permanent inactivation of the enzyme

44
Q

What are competitive inhibitors?

A

Binds only to free enzyme and competes with the active site

  • thus usually resembles the shape and structure of the substrate
  • reduces number of ES complexes by taking up enzymes as part of their EI complexes
45
Q

How do competitive inhibitors affect Vm?

A

They don’t!

46
Q

How do competitive inhibitors affect Km?

A

Increases it! (i.e. decreases the apaprent binding affinity)

47
Q

How do competitive inhibitors affect the catalytic efficiency?

A

Decrease!

48
Q

Can the effects of competitive inhibitors be overcome?

A

Yes! By increasing the amount of substrate

49
Q

When are competitive inhibitors most effective?

A

When substrate concentration is low

50
Q

Many drugs are ______ or ________ analogs

A

Substrate or transition-state

51
Q

Are substrate or transition-state analogs more potent inhibitors?

A

Transition-state because they bind more tightly

52
Q

How do uncompetitive inhibitors work?

A

Bind to the ES complex NOT at the active site/enzyme alone

53
Q

How do uncompetitive inhibitors affect Vm?

A

Decreases

54
Q

How do uncompetitive inhibitors affect Km?

A

Decreases

55
Q

How do uncompetitive inhibitors affect catalytic efficiency (kcat)?

A

No change

56
Q

Can increasing substrate concentration overcome the effects of uncompetitive inhibition?

A

No

57
Q

Do rate constants change in the presence of inhibitors?

A

NO! They just APPEAR to change (hence the term “apparent Km/Vm etc.”)

58
Q

At very low substrate concentrations, are uncompetitive inhibitors successful?

A

No, but it becomes more and more powerful as you increase your substrate concentration

59
Q

What is a noncompetitive inhibitor?

A

Binds to free enzymes or ES complex at a site different than the active site.

Hinders the reaction by distorting enzyme structure and preventing alignment of the catalytic center

60
Q

How do noncompetitive inhibitors affect Vmax?

A

Decrease

61
Q

How do noncompetitive inhibitors affect Km?

A

No change…the substrate doesnt really care if the inhibitor is there or not. Itll bind fine regardless

62
Q

How do noncompetitive inhibitors affect catalytic efficiency (Kcat)?

A

Decrease

63
Q

Does increasing the substrate concentration overcome the effects of noncompetitive inhibitors?

A

No

64
Q

What common antibiotic is an example of a noncompetitive inhibitor?

A

Doxycycline

65
Q

What type of inhibitor decreases both Vm AND Km?

A

Uncompetitive

66
Q

How does allosteric control work?

A

Allosteric enzymes operate by positive cooperativity: binding of substrate to one active site increases activity of other active sites.

67
Q

What effect do allosetic enzymes have on Km?

A

Usually decreases with increasing substrate concentration

68
Q

How do binding curves of allosteric enzymes appear?

A

S-shaped

69
Q

Allosteric enzymes are typically ______-______ enzymes

A

Rate-determining

70
Q

What is allosteric control?

A

Noncovalent binding of a ligand (effector) to a site other than the active site, thereby affecting the activity of the active site

71
Q

What is a homotropic effector?

A

Effector is the same as the substrate

Site is usually adjacent to active site

Interaction almost always increases activity

72
Q

What is heterotropic effector?

A

An effector that is the different than the substrate

Usually distant from the active site

Can increase or decrease activity

73
Q

Allosteric control operates by effector- induced conformational changes that alter activity by changing ___, ____, or both.

A

Km (K class) or Vm (V class)

74
Q

Are allosteric enzymes generally oligomers with multiple subunits and active sites?

A

Yes

75
Q

How is ATCase affected by allosteric control?

A

Aspartate will bind to the enzyme when in the tense state, pushing it into the relaxed state and increasing the reaction rate in an exponential way (S-shaped curve)

OR

CTP can also bind and stabilize the tense state, pushing the curve to the right

76
Q

How is PKA an example of allosteric regulation?

A

Examples of protein binding increasing or decreasing activity:

2 subunits are regulatory
2 subunits are catalytic

cAMP binds to the active sites and pulls the regulator units away, allowing PKA to become active

77
Q

How do reversible covalent modifications affect enzyme activity?

A

Charged groups such as phosphate, sulfate, or acetate, can bind enzymes and cause conformational changes that alter function.

78
Q

What is the most common form of reversible covalent modifications to regulate enzyme activity?

A

Phosphorylation/dephosphorylation
via kinases and phosphatases

Each step is considered IRREVERSIBLE even if the process as a whole is reversible (i.e. there are 2 different enzymes/2 different reactions to complete the cycle).

Molecules to Cells (34 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions