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2ND SEM BIOCHEMISTRY > PPT Enzyme: Regulation Of Activity - Dr. Bonleon > Flashcards

PPT Enzyme: Regulation Of Activity - Dr. Bonleon Flashcards

1
Q

Cannot respond to an increase in substrate concentration

A

Maximal rate

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2
Q

Average intracellular concentration of their substrates tends to be close to the __________.

A

Km value

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3
Q

Changes in substrate concentration generate corresponding changes in ___________.

A

Metabolic flux

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4
Q

Coordinating metabolite flow and maintaining homeostasis in quiescent cells

A

Passive

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5
Q

Limited scope for responding to changes in environmental variables

A

Passive

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6
Q

Responses to changes

A

Passive

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7
Q

Mean concentrations of metabolic intermediates remain relatively constant over time

A

Dynamic steady state

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8
Q

With overall change in free energy that favors UNIDRECTIONAL metabolite flow

A

Coupled metabolic reactions

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9
Q

Pathway with a large overall negative charge in free energy

A

Unidirectional flow

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10
Q

Bends or kink (enzyme cat steps)

A

Unidirectional flow

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11
Q

Ability to maintain a constant intracellular environment despite changes in the external environment

A

Homeostasis

*Organisms respond to changes (external and internal)

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12
Q

Balanced, coordinated changes in the rates of specific metabolic reactions

A

Homeostasis

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13
Q

Ensures metabolic efficiency

A

Compartmentation

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14
Q

Simplifies regulation

A

Compartmentation

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15
Q

Anabolic and catabolic pathways that interconvert common products may take place in specific subcellular compartments

A

Compartmentation

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16
Q

Segregation of metabolic pathways

A

Compartmentation

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17
Q

One or more unique intermediates can permit opposing pathways to coexist even in the absence of physical barrier

A

Physical compartmentation

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18
Q

Enzymes discriminate between the structurally similar conezymes

A

Compartmentation

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19
Q

Quantity or catalytic efficiency dictates that the reaction or catalysis is slow relative to all others in the pathway

A

Ideal enzyme

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20
Q

Reduces metabolite flux through the entire pathway

A

Rate-limiting reaction

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21
Q

Increase in either its quantity of catalytic efficiency enhances flux through the pathway as a whole

A

Ideal enzyme

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22
Q

Catalyze the rate-limiting steps

A

Ideal enzyme

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23
Q

Constitute efficient targets for regulatory intervention

A

Ideal enzyme

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24
Q

Product of the concentration of enzyme molecules and their intrinsic catalytic efficiency.

A

Catalytic capacity of the rate-limiting reaction in a metabolic pathway

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25
Q

Influenced by both changing the quantity of enzyme present and by altering its intrinsic catalytic efficiency

A

Catalytic capacity

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26
Q

Enzymes whose concentrations remain constant over time.

A

Constitutive enzymes

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27
Q

Substrates or structurally related compounds that initiate their syntheis and depended on by other enzymes

A

Inducers

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28
Q

Way by which an excess of a metabolite may curtail synthesis of its cognate enzyme

A

Repression

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29
Q

Absolute quantity of an enzyme reflects the net balance between enzyme synthesis and enzyme degradation

A

Enzyme degradation

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30
Q

Net result of enzyme synthesis and degradation

A

Protein turnover

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31
Q

Body is in a state of ______________

A

Dynamic equilibrium

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32
Q

__________ and ___________ is a continuous process.

A

Synthesis and degradation

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33
Q

Enzyme levels respond to:

A
  1. Physiologic
  2. Hormonal
  3. Dietary
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34
Q

Proteolytic degradation influenced by presence of ___________, substrates, coenzymes or metal ions that alter protein conformation.

A

Ligands

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35
Q

Changes in ______ can alter ionization state of the substrate or the enzyme-binding site for substrate.

A

pH

36
Q

Changes in _______ can alter ionization state at the catalytic site on the enzyme

A

pH

37
Q

Changes in pH can alter _________ so that their conformation and catalytic activity change

A

Protein molecules

38
Q

Rate of an enzyme-catalyzed reaction __________ in temperature up to an optimum point then it _______ because enzymes are THERMOLABILE.

A

Increase

Decrease

39
Q

If the product accumulates, it can inhibit some enzymes.

A

Product inhibition

40
Q

Limits the rate of formation of the product when the product is underused.

A

Product inhibition

41
Q

Inhibition of an enzyme in a biosynthetic pathway by end products of that pathway not by “backing-up” of intermediates but from the ability of the end product to bind to and inhibit the enzyme.

A

Feedback inhibition

42
Q

Intrinsic catalytic efficiency effected by binding of dissociable ligands.

A

Allosteric regulation

43
Q

Serve long-term adaptive requirements

A

Changes in protein level

44
Q

For rapid and transient alterations in metabolite flux

A

Changes in catalytic efficiency

45
Q

Key regulatory enzymes (committed steps) subjected

A

Allosteric regulation

46
Q

Activity modulated by binding of allosteric effectors to a site on the enzyme distinct from the active site

A

Allosteric regulation

47
Q

Negative modulation of the committed step of a metabolic pathway by its end product.

A

Feedback inhibition

48
Q

Prevents unnecessary production of an excess of end product by shutting down the pathway until more is needed

A

Feedback inhibition

49
Q

End product binds at an ___________.

A

Allosteric site

*Distinct from the catalytic site of the target enzyme

50
Q

If they enhance the rate of a reaction

A

Positive

51
Q

Activators

A

Positive

52
Q

If they decrease the rate of reaction

A

Negative

53
Q

Inhibitors

A

Negative

54
Q

Bear little or no structural similarity to the substrates of the enzymes they inhibit

A

Allosteric effectors

55
Q

End product may acts as “______________”

A

Negative allosteric effector

56
Q

Small molecule building blocks of macromolecules

A

Allosteric effectors

57
Q

Typically inhibit the 1st committed step in a biosynthetic sequence

A

Allosteric effectors

58
Q

End product typically only partially inhibits catalytic activity

A

Cooperative feedback inhibition

59
Q

Effect of an excess of 2 or more end products may be strictly additive or greater than their individual effect

A

Cooperative feedback mechanism

60
Q

Effectors are not isosteric with a substrate

A

Allosteric regulation

61
Q

Lack of structural similarity between a feedback inhibitor and the substrate for the enzyme whose activity it regulates.

A

Allosteric regulation

62
Q

Occupy another space

A

Allosteric

63
Q

Physically distinct from the catalytic site

A

Allosteric regulation

64
Q

Those whose activity at the active site may be modulated by the presence of effectors an allosteric site

A

Allosteric enzymes

65
Q

Substrate saturation kinetics are competitive

A

K-series

66
Q

The Km is raised without an effect in Vmax

A

K-series

67
Q

Conformational change may weaken the bonds between substrate and substrate-binding residues

A

K-series

68
Q

Allosteric inhibitor lowers Vmax without affecting the Km

A

V-series

69
Q

Alterations in Km and Vmax result from conformational changes at the catalytic site induced by binding of the allosteric effector at the allosteric site

A

V-series

70
Q

Primary effect may be to alter the orientation or charge of catalytic residues, lowering vmax

A

V-series

71
Q

The addition of a phosphate group to a specific amino acid residue (Ser, Tyr, Thr) by specific protein kinases dramatically enhance or depress activity

A

Phosphorylation

72
Q

May be dephosphorylated by specific phosphatases and reversible

A

Phosphorylation

73
Q

Activities of some enzymes are regulated by the reversible addition of a nucleotide to a specific amino acid.

A

Nucleotidylation

74
Q

An adenylated enzyme may be deadenylated by a specific enzyme and reversible.

A

Nucleotidylation

75
Q

Some enzymes are synthesized as proenzymes or zymogens (inactive forms)

A

Proteolytic cleavage

76
Q

Activated by being cleaved at a specific site in their polypeptide chain by specific proteases

A

Proteolytic cleavage

77
Q

Digestive enzymes that hydrolyze proteins

A

Proteolytic cleavage

78
Q

Blood clotting mediated by proteolytic zymogen activities of several serum enzymes

A

Proteolytic cleavage

79
Q

Devoid of mechanistic implications

A

Feedback regulations

80
Q

Mechanism for regulation of enzyme activity

A

Feedback inhibition

81
Q

Virtually all reactions in the body are mediated by____________.

A

enzymes

82
Q

____________ are protein catalysts that increase the rate of reactions without being changed in the overall process.

A

Enzymes

83
Q

Enzymes selectively channel reactants (__________) into useful pathways.

A

substrates

84
Q

Enzymes are ___________ increase the velocity of a chemical reaction.

A

catalysts

85
Q

_____________ isolate the reaction substrate or product from other competing reactions m provide purposeful pathways.

A

Compartmentalization

2ND SEM BIOCHEMISTRY (33 decks)

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