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Biochem > EXAM 3 (2) > Flashcards

EXAM 3 (2) Flashcards

(80 cards)

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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
What does EC stand for?
Enzyme Commission
26
Specificity constant =
Kcat/Km = m^-1s^-1
27
Mole
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
28
Molarity
Unit of concentration of mol/L
29
Active Site
Where the substrate binds to the enzyme; inhibitors may also bind here; site of catalysis
30
Transition State
Arrangement of unstable, highly energyed atoms in which bonds are being broken and formed
31
Acid-Base Catalysis
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
32
Allosteric Regulation
Reversible noncovalent binding of modulator molecule the occurs NOT at active site
33
Covalent Modification
Reversible, covalent addition of group to enzyme; Modification occurs to specific amino acid
34
Inhibitor molecule resembles substrate molecule and competes for binding at active site
Competitive Inhibition Same Vmax High I = low Vmax
35
The effect on Km with no observable effect on Vmax
Diagnostic Competitive Inhibition
36
Inhibitor binds to a site located away from active site
Noncompetitive Inhibition | Same Km
37
Inhibitor will bind only to ES complex
Uncompetitive Inhibitor
38
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
Suicide Inhibitors
39
Reaction product of one enzyme becomes the S of the next enzyme and so on
Regulatory Enzymes
40
One enzyme sets the rate of the overall sequence because it catalyzes the slowest ______ ________ step
Rate Limiting | This is the regulatory enzyme aka rate limiting enzyme
41
Each metabolic pathway is ______ _________ to meet changes in cellular demand
Constantly Adjusted
42
Reversible, noncovalent binding of modulator molecule to change conformation
Allosteric Enzyme
43
Many times the allosteric enzyme is inhibited by the ________ _______. Regulation of this type is ______________.
End Product | Feedback Inhibition
44
Reversible, covalent addition of a group to enzyme and modification occurs to specific amino acids
Covalent Modification
45
Vmax
Max Velocity
46
Km
Michaelis-Menten Constant | Combine Rate Constant
47
Kcat
Turnover number Catalytic Rate Product Formation Rate
48
Specificity Constant
kcat/Km = m^-1s^-1
49
Catalytic Rate
kcat
50
Modulate Enzyme activity
Effectors (Activators or Inhibitors)
51
__________ depends on how efficiently reactants can reach a transition state.
Rate of Reaction
52
Stable structures that resemble transition state structures
Transition State Analogs (inactivates enzymes)
53
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
Facilitation of Proximity
54
Mechanism that raises the effective concentration of reactants
Facilitation of Proximity
55
A means to artificially raise reactant concentration so the reaction is faster
Facilitation of Proximity
56
Amino acid in active site with nucleophilic R-groups attack electrophilic parts of the substrate forming covalent bonds between E and S
Covalent Catalyst
57
Usually happens with transferases
Covalent Catalyst
58
Transfer of a proton in the transition state
Acid-Base Catalysis
59
Rate enhancement is only about 100
Acid-Base Catalysis
60
Groups that can act as acid or base in Acid-Base Catalysis
Glu, His, Tyr, Cys
61
This mechanism is dependent on pKa of the R-groups that are in the active site and on pH optimum of the enzyme
Acid-Base Catalysis
62
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
Molecular Distortion/Strain
63
When enzyme binds to active site, strain is placed on reactant
Molecular Distortion/Strain
64
Molecular Distortion/Strain
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
Typically employed in assaying lipid-dependent enzyme activity
Mixed Micelle System
66
Mixed micelle system is composed of
Nonionic detergent Triton X-100 and lipid
67
Alternative enzyme kinetics for hydrophobic enzymes and substrates
Surface Dilution Kinetics
68
3-D bulk interactions
Clumps of insoluble material | Interactions between enzyme and substrate where substrate is not associated with micelle
69
2-D Surface Interactions
Occur on the membrane
70
Lineweaver Burk Plot
Double Reciprocal Plot x-int = 1/-Km (same units as substrate) y-int = 1/Vmax (same units as Velocity)
71
Eadie-Hofstee Plot
``` y-int = Vmax/Km x-int = Vmax ```
72
Competitive Inhibition Graph
Same Vmax | Slope = Km/Vmax
73
Noncompetitive Inhibition Graph
Same Km | x-int = 1/-km
74
Uncompetitive Inhibition Graph
3 Parallel Lines | S and I (not S1 and S2 like Ping Pong)
75
Ternary Complex Formation
Random Binding = Doesn't matter | Ordered Binding = Conformation of Enzyme is altered with substrate which allows S2 to bind
76
Ping Pont
Three parallel lines S1 and S2 Enzyme catalyzes before substrate comes in Enzyme can only bind to S2 in modified form
77
A direct measure of reaction efficiency
kcat/Km
78
Substrate Specificity
kcat/Km | High if Enzyme and substrate like to bind
79
Per-steady state
ES builds up
80
Steady state
ES remains constant

Biochem (11 decks)

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