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Biochem > EXAM 3 (2) > Flashcards

EXAM 3 (2) Flashcards

1
Q

A given enzyme has a range of specificity for its substrate that is…

A

Very narrow

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2
Q

T/F. Enzymes bind to their substrates at a region on the substrate called an active site.

A

False

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3
Q

Enzyme cofactors are _______ bound to the proteins?

A

Non-covalently

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4
Q

Enzyme prosthetic groups are _________ bound to the enzyme

A

Covalently

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5
Q

Binding of an enzyme to its substrate ________ its activation energy.

A

Lowers

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6
Q

T/F. Transition state analogs are structurally stable molecules with a very short half life.

A

False

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7
Q

The enzyme mechanism that yields only about 100 fold increase in reaction rate enhancement

A

Acid-base Catalysis

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8
Q

T/F. The pre-steady state is a period where ES build up equals the ES breakdown.

A

False

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9
Q

Kcat is an abbreviation for

A

Catalytic Rate

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10
Q

Combined constant rate

A

Km

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11
Q

T/F. When Vmax equals 2V, Km equals substrate concentration.

A

True

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12
Q

T/F. Up to a point, Vo increases the substrate concentration is increased.

A

True

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13
Q

Double reciprocal plot such as Lineweaver-Burk Plot are used in enzyme kinetics analysis to get a more accurate

A

Vmax

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14
Q

When an inhibitor of an enzyme binds on to ES complex, the inhibition is

A

Uncompetitive

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15
Q

_______________ is the alternative name given to the mechanism based inactivator.

A

Suicide Inhibitor

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16
Q

Two major types of Regulatory Enzymes

A

Covalent Modification or Allosteric Enzyme

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17
Q

The only known example of a nonprotein biological catalyst

A

rRNA

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18
Q

When every enzyme molecule in a reaction mixture is bound to a substrate, the enzyme is said to be __________.

A

Saturated

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19
Q

Method said to determine properties of enzymes of very hydrophobic substrates, such as lipids

A

Surface Dilution Kinetics

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20
Q

The period of time an enzyme catalyzed reaction and concentration of the enzyme substrate compile remains stable is called

A

The Steady-State

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21
Q

Michaelis and Menten assumed for a period of time the enzyme catalyzed reaction formation rate of the enzyme substrate complex is essentially equal to the breakdown of the enzyme substrate complex. This is known as

A

The Steady-State Assumption

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22
Q

Add phosphate

A

Kinases

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23
Q

Remove phosphate

A

Phosphatases

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24
Q

List the 6 classes of Enzymes in order with their EC number.

A

EC.1.X.X.X… OTHLIL

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25
Q

What does EC stand for?

A

Enzyme Commission

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26
Q

Specificity constant =

A

Kcat/Km = m^-1s^-1

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27
Q

Mole

A

Unit that describes the number of particles;

One gram molecular weight of a complex; A mole contains 6.02 X 10^23 atoms of any element

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28
Q

Molarity

A

Unit of concentration of mol/L

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29
Q

Active Site

A

Where the substrate binds to the enzyme; inhibitors may also bind here; site of catalysis

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30
Q

Transition State

A

Arrangement of unstable, highly energyed atoms in which bonds are being broken and formed

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31
Q

Acid-Base Catalysis

A

When a proton is transferred during the transition state; Glue, His, Tys, Cys R-groups can act as either an acid, protinated, or base, unprotinated

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32
Q

Allosteric Regulation

A

Reversible noncovalent binding of modulator molecule the occurs NOT at active site

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33
Q

Covalent Modification

A

Reversible, covalent addition of group to enzyme; Modification occurs to specific amino acid

34
Q

Inhibitor molecule resembles substrate molecule and competes for binding at active site

A

Competitive Inhibition
Same Vmax
High I = low Vmax

35
Q

The effect on Km with no observable effect on Vmax

A

Diagnostic Competitive Inhibition

36
Q

Inhibitor binds to a site located away from active site

A

Noncompetitive Inhibition

Same Km

37
Q

Inhibitor will bind only to ES complex

A

Uncompetitive Inhibitor

38
Q

Become reactive after binding to active site and instead of being converted to normal products it is converted to a highly reactive product that binds irreversibly to enzyme

A

Suicide Inhibitors

39
Q

Reaction product of one enzyme becomes the S of the next enzyme and so on

A

Regulatory Enzymes

40
Q

One enzyme sets the rate of the overall sequence because it catalyzes the slowest ______ ________ step

A

Rate Limiting

This is the regulatory enzyme aka rate limiting enzyme

41
Q

Each metabolic pathway is ______ _________ to meet changes in cellular demand

A

Constantly Adjusted

42
Q

Reversible, noncovalent binding of modulator molecule to change conformation

A

Allosteric Enzyme

43
Q

Many times the allosteric enzyme is inhibited by the ________ _______. Regulation of this type is ______________.

A

End Product

Feedback Inhibition

44
Q

Reversible, covalent addition of a group to enzyme and modification occurs to specific amino acids

A

Covalent Modification

45
Q

Vmax

A

Max Velocity

46
Q

Km

A

Michaelis-Menten Constant

Combine Rate Constant

47
Q

Kcat

A

Turnover number
Catalytic Rate
Product Formation Rate

48
Q

Specificity Constant

A

kcat/Km = m^-1s^-1

49
Q

Catalytic Rate

A

kcat

50
Q

Modulate Enzyme activity

A

Effectors (Activators or Inhibitors)

51
Q

__________ depends on how efficiently reactants can reach a transition state.

A

Rate of Reaction

52
Q

Stable structures that resemble transition state structures

A

Transition State Analogs (inactivates enzymes)

53
Q

Reaction rate between two molecules is enhanced when enzyme removes them from dilute solution and holds them in close proximity to each other in the active site

A

Facilitation of Proximity

54
Q

Mechanism that raises the effective concentration of reactants

A

Facilitation of Proximity

55
Q

A means to artificially raise reactant concentration so the reaction is faster

A

Facilitation of Proximity

56
Q

Amino acid in active site with nucleophilic R-groups attack electrophilic parts of the substrate forming covalent bonds between E and S

A

Covalent Catalyst

57
Q

Usually happens with transferases

A

Covalent Catalyst

58
Q

Transfer of a proton in the transition state

A

Acid-Base Catalysis

59
Q

Rate enhancement is only about 100

A

Acid-Base Catalysis

60
Q

Groups that can act as acid or base in Acid-Base Catalysis

A

Glu, His, Tyr, Cys

61
Q

This mechanism is dependent on pKa of the R-groups that are in the active site and on pH optimum of the enzyme

A

Acid-Base Catalysis

62
Q

Strain is induced in the bond system of the reactants and the release of the strain as the transition state converts to products provides the rate enhancement when the substrate is removed and converts into product

A

Molecular Distortion/Strain

63
Q

When enzyme binds to active site, strain is placed on reactant

A

Molecular Distortion/Strain

64
Q

Molecular Distortion/Strain

A

When enzyme binds to active site, strain is placed on reactant and substrate is highly energized. Enzyme lets go and that releases the energy in the transition state to push the substrate into product

65
Q

Typically employed in assaying lipid-dependent enzyme activity

A

Mixed Micelle System

66
Q

Mixed micelle system is composed of

A

Nonionic detergent Triton X-100 and lipid

67
Q

Alternative enzyme kinetics for hydrophobic enzymes and substrates

A

Surface Dilution Kinetics

68
Q

3-D bulk interactions

A

Clumps of insoluble material

Interactions between enzyme and substrate where substrate is not associated with micelle

69
Q

2-D Surface Interactions

A

Occur on the membrane

70
Q

Lineweaver Burk Plot

A

Double Reciprocal Plot
x-int = 1/-Km (same units as substrate)
y-int = 1/Vmax (same units as Velocity)

71
Q

Eadie-Hofstee Plot

A 
y-int = Vmax/Km
x-int = Vmax
72
Q

Competitive Inhibition Graph

A

Same Vmax

Slope = Km/Vmax

73
Q

Noncompetitive Inhibition Graph

A

Same Km

x-int = 1/-km

74
Q

Uncompetitive Inhibition Graph

A

3 Parallel Lines

S and I (not S1 and S2 like Ping Pong)

75
Q

Ternary Complex Formation

A

Random Binding = Doesn’t matter

Ordered Binding = Conformation of Enzyme is altered with substrate which allows S2 to bind

76
Q

Ping Pont

A

Three parallel lines S1 and S2
Enzyme catalyzes before substrate comes in
Enzyme can only bind to S2 in modified form

77
Q

A direct measure of reaction efficiency

A

kcat/Km

78
Q

Substrate Specificity

A

kcat/Km

High if Enzyme and substrate like to bind

79
Q

Per-steady state

A

ES builds up

80
Q

Steady state

A

ES remains constant

Biochem (11 decks)

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