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biochem lec > Enzymes > Flashcards

Enzymes Flashcards

1
Q

the enzyme that directly uses oxygen during respiration.

A

cytochrome c oxidase

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2
Q

A biological catalyst

A

Enzyme

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3
Q

With the exception of some ____ that catalyze their own self-cleavage, all enzymes are proteins.

A

RNAs

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4
Q

Enzymes can increase the _____ by a factor of 10^9 to 10^20 over an uncatalyzed reaction.

A

rate of a reaction

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5
Q

enzymes that catalyze the reactions of only L-amino acids.

A

stereoselective

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6
Q

Others catalyze reactions of specific types of compounds or bonds; for example, ________ catalyzes hydrolysis of peptide bonds formed by the carboxyl groups of Lys and Arg.

A

trypsin

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7
Q

Enzymes are classified into six major groups according to the type of reaction catalyzed:

A
  • Oxidoreductases
  • Transferases
  • Hydrolases
  • Lyases
  • Isomerases
  • Ligases
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8
Q

Oxidation-reduction reactions.

Classification of Enzymes

A

Oxidoreductases

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9
Q

Group transfer reactions.

Classification of Enzymes

A

Transferases

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10
Q

Hydrolysis reactions

Classification of Enzymes

A

Hydrolases

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11
Q

Addition of two groups to a C-C double bond, or removal of two groups to create a C-C double bond.

Classification of Enzymes

A

Lyases

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12
Q

Isomerization reactions

Classification of Enzymes

A

Isomerases

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13
Q

The joining to two molecules.

Classification of Enzymes

A

Ligases

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14
Q

The protein part of an enzyme.

A

Apoenzyme

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15
Q

A nonprotein portion of an enzyme that is necessary for catalytic function; examples are metallic ions such as Zn2+ and Mg2+.

A

Cofactor

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16
Q

A nonprotein organic molecule, frequently a B vitamin, that acts as a cofactor.

A

Coenzyme

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17
Q

The compound or compounds whose reaction an enzyme catalyzes

A

Substrate

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18
Q

The specific portion of the enzyme to which a substrate binds during reaction

A

Active site

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19
Q

What are the participating components?

Schematic of an Active Site

A
  • Apoenzyme
  • Substrate molecule
  • coenzyme molecule
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20
Q

Any process that initiates or increases the activity of an enzyme

A

Activation

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20
Q

Any process that makes an active enzyme less active or inactive.

A

Inhibition

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21
Q

A substance that binds to the active site of an enzyme thereby preventing binding of substrate.

A

Competitive inhibitor

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22
Q

Any substance that binds to a portion of the enzyme other than the active site and thereby inhibits the activity of the enzyme

A

Noncompetitive inhibitor

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23
Q

A measure of how much a reaction rate is increased.

A

Enzyme activity

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24
Q

We examine how the rate of an enzyme-catalyzed reaction is affected by:

A
  • Enzyme concentration.
  • Substrate concentration.
  • Temperature.
  • pH.
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25
Q

The effect of enzyme concentration on the rate of an enzyme-catalyzed reaction. Substrate concentration, temperature, and pH are constant

A

Directly proportional

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26
Q

The effect of substrate concentration on the rate of an enzyme-catalyzed reaction. Enzyme concentration, temperature, and pH are constant.

A

Rises and then stabilizes

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27
Q

The effect of temperature on the rate of an enzyme-catalyzed reaction. Substrate and enzyme concentrations and pH are constant

A

Rate increases between 30 to 40 degrees celcius

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28
Q

The effect of pH on the rate of an enzyme-catalyzed reaction. Substrate and enzyme concentrations and temperature are constant.

A

Rate increases between pH 6 - 7

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29
Q

The enzyme is a rigid three-dimensional body.

Mechanism of Action

A

Lock-and-key model

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30
Q

The enzyme surface contains the active site.

Mechanism of Action

A

Lock-and-key model

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31
Q

The active site becomes modified to accommodate the substrate

Mechanism of Action

A

Induced-fit model

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32
Q

When a competitive inhibitor enters the active site, the substrate cannot enter.

Mechanism of Action

A

The mechanism of competitive inhibition

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33
Q

The inhibitor binds itself to a site other than the active site (allosterism), thereby changing the conformation of the active site.

Mechanism of Action

A

Mechanism of noncompetitive inhibition

34
Q

The substrate still binds but there is no catalysis.

Mechanism of Action

A

Mechanism of noncompetitive inhibition

35
Q

What do you call it if the inhibitor binds itself to a site other than the active site

Mechanism of Action

A

allosterism

36
Q

Both the lock-and-key model and the induced-fit model emphasize the ____ of the active site

A

shape

37
Q

Both the lock-and-key model and the induced-fit model emphasize the shape of the active site. However, the _______ of the active site is the most important.

Mechanism of Action

A

chemistry

38
Q

The five amino acids that participate in the active site in more than 65% of the enzymes studied to date.

Mechanism of Action

A

His > Cys > Asp > Arg > Glu.

39
Q

These five are His > Cys > Asp > Arg > Glu.
Four of these amino acids have either ___________; the fifth has a __________

Mechanism of Action

A
  • acidic or basic side chains
  • sulfhydryl group (-SH).
40
Q

Enzymes provide an ______________ for reaction.

A

alternative pathway

41
Q

An enzyme-regulation process where the product of a series of enzyme-catalyzed reactions inhibits an earlier reaction in the sequence.

Enzyme Regulation

A

Feedback control

42
Q

In Feedback control, The inhibition may be __________ or ____________

A

competitive or noncompetitive

43
Q

An inactive form of an enzyme that must have part of its polypeptide chain hydrolyzed and removed before it becomes active

A

Proenzyme (zymogen)

44
Q

An example of Proenzyme (zymogen):

A

trypsin, a digestive enzyme.

45
Q

Trypsin is synthesized and stored as _________-, which has no enzyme activity.

A

trypsinogen

46
Q

trypsinogen becomes active only after a _______________ is hydrolyzed and removed from the N-terminal end of its chain.

A

six-amino acid fragment

47
Q

Removal of the six-amino acid fragment changes not only the primary structure but also the _______, allowing the molecule to achieve its active form.

A

tertiary structure

48
Q

Enzyme regulation based on an event occurring at a place other than the active site but that creates a change in the active site.

A

Allosterism

49
Q

An enzyme regulated by allosterism is called an ____________

A

allosteric enzyme.

50
Q

Allosteric enzymes often have __________

A

multiple polypeptide chains

51
Q

Inhibition of an allosteric enzyme.

A

Negative modulation

52
Q

Stimulation of an allosteric enzyme.

A

Positive modulation

53
Q

A substance that binds to an allosteric enzyme.

A

Regulator

54
Q

Binding of the regulator to a site other than the active site changes the shape of the active site.

A

The allosteric effect.

55
Q

The process of affecting enzyme activity by covalently modifying it.

A

Protein modification

56
Q

The best known examples of protein modification involve ________________

A

phosphorylation/
dephosphorylation.

56
Q

Pyruvate kinase (PK) is the active form of the enzyme; it is inactivated by ____________to pyruvate kinase phosphate (PKP).

A

phosphorylation

57
Q

An enzyme that occurs in multiple forms; each catalyzes the same reaction.

A

Isoenzyme (Isozymes)

58
Q

Example of an Isoenzyme - ________________ catalyzes the oxidation of lactate to pyruvate.

A

lactate dehydrogenase (LDH)

59
Q

The enzyme is a tetramer of H and M chains.

A

lactate dehydrogenase (LDH)

60
Q

is present predominately in heart muscle.

A

H4

60
Q

is present predominantly in the liver and in skeletal muscle.

A

M4

61
Q

Hepatitis

Enzyme Assays in medicine

A

Alanine amino transferase (ALT)

62
Q

Prostate cancer

Enzyme Assays in medicine

A

Acid Phosphatase

63
Q

Liver or Bone disease

Enzyme Assays in medicine

A

Alkaline phosphatase (ALP)

64
Q

Pancreatic disease or mumps

Enzyme Assays in medicine

A

Amylase

65
Q

Heart Attack or Hepatitis

Enzyme Assays in medicine

A

Aspartate aminotransferase (AST)

66
Q

Heart Attack

Enzyme Assays in medicine

A
  • Lactate dehydrogenase (LDH)
  • Creatine phosphokinase (CPK)
  • Phosphohexose isomerase (PHI)
67
Q

A molecule whose shape mimics the transition state of a substrate.

A

Transition state analog

68
Q

Pyrrole-2-carboxylate mimics the planar transition state of the reaction

A

The proline racemase reaction

69
Q

An antibody that has catalytic activity because it was created using a transition state analog as an immunogen.

A

Abzyme

70
Q

Trypsin catalyzes the hydrolysis of peptide bonds formed by the carboxyl group of ___________ and __________-/

A

lysine and arginine.

71
Q

What enzyme turns Pyruvate to Lactate?

Oxidoreductase

A

lactate dehydrogenase

72
Q

What enzyme turns Aspartate
a-Ketoglutarate to Oxaloacetate + Glutamate?

Transferase

A

Aspartate amino transferase

73
Q

What enzyme turns Acetylcholine to Acetate + Choline

Hydrolase

A

Acetylcholinesterease

74
Q

What enzyme turns cis-Aconitate to Isocitrate

Lyase

A

Acotinase

75
Q

What enzyme turns
a-D-Glucose-6-phospate to a-D-Fructose-6-phosphate

Isomerase

A

Phosphohexose Isomerase

76
Q

What enzyme turns ATP + L-tyrosine + t-RNA to L-tyrosyl-tRNA + AMP + PP

Ligase

A

Tyrosine-tRNA synthetase

77
Q

The 5 tetramers of lactate dehydrogenase

A
  • M4
  • M3H
  • M2H2
  • MH3
  • H4
77
Q

Can exist in either of two states: R0 orT0

A

Dimeric Protein

78
Q

Pyrrole-2-carboxylate mimics the planar transition state of what reaction?

A

L-Proline to D-Proline

79
Q

The abzyme is then used to catalyze the reaction D-Alaninw + Pyridoxial 5’-P to Pyruvate + Pyridoxamine 5’-P

A

N^a-(5’-Phosphopyridoxyl)-L-lysine moiety (antigen)

biochem lec (10 decks)

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