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Biochemistry Broyles > Enzymes Kinetics, Inhibition, and Control Ch.12 > Flashcards

Enzymes Kinetics, Inhibition, and Control Ch.12 Flashcards

1
Q

What will reduce the amount of cholesterol that we make?

A

Atorvastatin (Lipitor)

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2
Q

What does kinetics refer to?

A

Rates

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3
Q

What doe enzyme kinetic rates refer to?

A

Reaction rates

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4
Q

What do reaction rates refer to?

A

the formation of product as a function of time.

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5
Q

What is the job of an enzyme?

A

To enhance the rate of the reaction.

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6
Q

If the Michaelis-Menten Equation for Enzyme Kineticas is determined early in its course what is considered?

A

products is considered to be low and K-2 ( rate constants) drops out of the equation. Back reaction is negligible.

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7
Q

What is KM?

A

A constant describing the affinity of an enzyme for its substrate.

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8
Q

In KM, the lower the constant what can be determined?

A

The higher the affinity for the substrate.

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9
Q

What gives half maximal VMAX?

A

KM is the S.

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10
Q

What is KM unique for?

A

each substrate of a given enzyme.

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11
Q

What is Kcat?

A

take the Vmax/ total enzyme concentration and it gives you the value of the turnover number.

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12
Q

What is the turnover number?

A

how fast the enzyme will come to a state that it can do it again.

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13
Q

What doe the most efficient reactions reflect a need for?

A

speed

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14
Q

KM should be what in vivo concentrations?

A

10^-2

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15
Q

Ethyl Ester is not something that happens in the cell normally what?

A

The 10^-1 is too big of a concentration to exist inside the cell naturally.

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16
Q

Why do enzyme inhibitors react reversably or irreversably with an enzyme?

A

to alter its Km and or Vmax values.

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17
Q

What alters the KM or Vmas values?

A

Enzymes inhibitors that interact reversibly or irreversibly with an enzyme

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18
Q

What does a competitive inhibitor bind to?

A

the enzymes active site

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19
Q

What does a competitive inhibitor increase?

A

the apparent Km for the reaction

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20
Q

What does an uncompetitive enzyme inhibitor affect?

A

catalytic activity such that both the apparent KM and the apparent Vmax decreases.

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21
Q

A mixed enzyme inhibitor alters both what?

A

catalytic activity and substrate binding.

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22
Q

What will occur with a mixed enzyme inhibitor?

A

Apparent Vmax decreases and the apparent KM may increase or decrease.

23
Q

What occurs in competitive inhibition?

A

The inhibitor binds to the enzyme’s substrate binding site.

24
Q

What does the inhibitor resemble in competitive inhibition?

A

the inhibitor structurally resembles the substrate but not always obvious to the eye.

25
Q

What is pyrazole?

A

a competitive inhibitor of alcohol dehydrogenase.

26
Q

What is tamiflu (oseltamivir)?

A

it is a competitive inhibitor of influenze neurominidase.

27
Q

What does Oseltamivir do?

A

Hydrolizes sialic acid.

28
Q

What is Adenosine Deaminase?

A

Transition State Analog Inhibitor.

29
Q

What two enzymes does HIV make?

A

reverse transcriptase and a protease.

30
Q

What is the reverse transcriptase that HIV makes do?

A

Replicate genome

31
Q

What does the protease that HIV makes do?

A

cleaves its polyprotein precursor into functional proteins.

32
Q

What is the most important point in regards to competitive enzyme inhibition?

A

inhibition can be overcome at high substrate concentration.

33
Q

What occurs in the uncompetitve enzyme inhibition?

A

inhibitor binds to the ES complex.

34
Q

What do allosteric effectors bind to?

A

multisubunit enzymes

35
Q

What are multisubunit enzymes?

A

aspartate transcarbamoylase

36
Q

What does the binding of allosteric effectors to multisubunit induce?

A

cooperative conformational changes that alter the enzyme’s catalytic activity.

37
Q

What can phosphorylation and dephosphorylation of an enzyme such as glycogen phosphorylase control?

A

its activity by shifting the equilibrium between more active and less active conformations.

38
Q

What is the first committed step in the biosynthesis of pyrimidines?

A

aspartate transcarbamoylase reaction.

39
Q

What is significant of the allosteric effectors: ATCase reaction graphs?

A

the curves are sigmoidal because the substrates bind cooperatively.

40
Q

Why does the pyrimidine biosynthesis ATCase feedback inhibition is activated by ATP?

A

To coordinate purine and pyrimidine biosynthesis (need equal amounts for RNA and DNA)

41
Q

What is the important point of ATCase: T-State vs R-state?

A

the regulatory subunits impose coopertivity on the catalytic subunits.

42
Q

What do regulatory subunits repress?

A

the catalytic subunits’ activity.

43
Q

Allosteric effects of a different molecule binds to an enzyme to what?

A

modify its activity

44
Q

CTP binds to what?

A

regulatory subunits to cause substrate binding site to close.

45
Q

Why does CTP cause substrate binding site to close?

A

inhibit enzyme activity

46
Q

What does CTP undergo this feedback inhibition?

A

it is the endproduct of the pathway

47
Q

What does ATP bind to in allosteric effect of enzyme activity?

A

To regulatory subunits to cause the substrate binding site to open and enhances activity.

48
Q

ATP is the product of what?

A

a parallel pathway.

49
Q

What does the parallel pathways mean when the ATP is the product of parallel pathways?

A

purine and pyrimidine nucleotides need to be present in nearly in equal amounts.

50
Q

Why do purines and pyrimidine nucleotides needs to be present in nearly equal amounts?

A

this serves to balance the levels of nucleotides in the cell.

51
Q

How is phosphorylation controlled?

A

by covalent modification.

52
Q

What is G1P a product of?

A

Glycogen phosphorylase

53
Q

Rabbit muscle glycogen phosphorylase causes a masking loop to do what?

A

move out of the way of the active site.

54
Q

What is atorvastatin (lipitor)?

A

inhibitor of HMG CoA reductase-rate limiting step in cholesterol synthesis.

Biochemistry Broyles (3 decks)

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