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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
We examine how the rate of an enzyme-catalyzed reaction is affected by:
- Enzyme concentration. - Substrate concentration. - Temperature. - pH.
25
The effect of enzyme concentration on the rate of an enzyme-catalyzed reaction. Substrate concentration, temperature, and pH are constant
Directly proportional
26
The effect of substrate concentration on the rate of an enzyme-catalyzed reaction. Enzyme concentration, temperature, and pH are constant.
Rises and then stabilizes
27
The effect of temperature on the rate of an enzyme-catalyzed reaction. Substrate and enzyme concentrations and pH are constant
Rate increases between 30 to 40 degrees celcius
28
The effect of pH on the rate of an enzyme-catalyzed reaction. Substrate and enzyme concentrations and temperature are constant.
Rate increases between pH 6 - 7
29
The enzyme is a rigid three-dimensional body. | Mechanism of Action
Lock-and-key model
30
The enzyme surface contains the active site. | Mechanism of Action
Lock-and-key model
31
The active site becomes modified to accommodate the substrate | Mechanism of Action
Induced-fit model
32
When a competitive inhibitor enters the active site, the substrate cannot enter. | Mechanism of Action
The mechanism of competitive inhibition
33
The inhibitor binds itself to a site other than the active site (allosterism), thereby changing the conformation of the active site. | Mechanism of Action
Mechanism of noncompetitive inhibition
34
The substrate still binds but there is no catalysis. | Mechanism of Action
Mechanism of noncompetitive inhibition
35
What do you call it if the inhibitor binds itself to a site other than the active site | Mechanism of Action
allosterism
36
Both the lock-and-key model and the induced-fit model emphasize the ____ of the active site
shape
37
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
chemistry
38
The five amino acids that participate in the active site in more than 65% of the enzymes studied to date. | Mechanism of Action
His > Cys > Asp > Arg > Glu.
39
These five are His > Cys > Asp > Arg > Glu. Four of these amino acids have either ___________; the fifth has a __________ | Mechanism of Action
- acidic or basic side chains - sulfhydryl group (-SH).
40
Enzymes provide an ______________ for reaction.
alternative pathway
41
An enzyme-regulation process where the product of a series of enzyme-catalyzed reactions inhibits an earlier reaction in the sequence. | Enzyme Regulation
Feedback control
42
In Feedback control, The inhibition may be __________ or ____________
competitive or noncompetitive
43
An inactive form of an enzyme that must have part of its polypeptide chain hydrolyzed and removed before it becomes active
Proenzyme (zymogen)
44
An example of Proenzyme (zymogen):
trypsin, a digestive enzyme.
45
Trypsin is synthesized and stored as _________-, which has no enzyme activity.
trypsinogen
46
trypsinogen becomes active only after a _______________ is hydrolyzed and removed from the N-terminal end of its chain.
six-amino acid fragment
47
Removal of the six-amino acid fragment changes not only the primary structure but also the _______, allowing the molecule to achieve its active form.
tertiary structure
48
Enzyme regulation based on an event occurring at a place other than the active site but that creates a change in the active site.
Allosterism
49
An enzyme regulated by allosterism is called an ____________
allosteric enzyme.
50
Allosteric enzymes often have __________
multiple polypeptide chains
51
Inhibition of an allosteric enzyme.
Negative modulation
52
Stimulation of an allosteric enzyme.
Positive modulation
53
A substance that binds to an allosteric enzyme.
Regulator
54
Binding of the regulator to a site other than the active site changes the shape of the active site.
The allosteric effect.
55
The process of affecting enzyme activity by covalently modifying it.
Protein modification
56
The best known examples of protein modification involve ________________
phosphorylation/ dephosphorylation.
56
Pyruvate kinase (PK) is the active form of the enzyme; it is inactivated by ____________to pyruvate kinase phosphate (PKP).
phosphorylation
57
An enzyme that occurs in multiple forms; each catalyzes the same reaction.
Isoenzyme (Isozymes)
58
Example of an Isoenzyme - ________________ catalyzes the oxidation of lactate to pyruvate.
lactate dehydrogenase (LDH)
59
The enzyme is a tetramer of H and M chains.
lactate dehydrogenase (LDH)
60
is present predominately in heart muscle.
H4
60
is present predominantly in the liver and in skeletal muscle.
M4
61
Hepatitis | Enzyme Assays in medicine
Alanine amino transferase (ALT)
62
Prostate cancer | Enzyme Assays in medicine
Acid Phosphatase
63
Liver or Bone disease | Enzyme Assays in medicine
Alkaline phosphatase (ALP)
64
Pancreatic disease or mumps | Enzyme Assays in medicine
Amylase
65
Heart Attack or Hepatitis | Enzyme Assays in medicine
Aspartate aminotransferase (AST)
66
Heart Attack | Enzyme Assays in medicine
- Lactate dehydrogenase (LDH) - Creatine phosphokinase (CPK) - Phosphohexose isomerase (PHI)
67
A molecule whose shape mimics the transition state of a substrate.
Transition state analog
68
Pyrrole-2-carboxylate mimics the planar transition state of the reaction
The proline racemase reaction
69
An antibody that has catalytic activity because it was created using a transition state analog as an immunogen.
Abzyme
70
Trypsin catalyzes the hydrolysis of peptide bonds formed by the carboxyl group of ___________ and __________-/
lysine and arginine.
71
What enzyme turns Pyruvate to Lactate? | Oxidoreductase
lactate dehydrogenase
72
What enzyme turns Aspartate a-Ketoglutarate to Oxaloacetate + Glutamate? | Transferase
Aspartate amino transferase
73
What enzyme turns Acetylcholine to Acetate + Choline | Hydrolase
Acetylcholinesterease
74
What enzyme turns cis-Aconitate to Isocitrate | Lyase
Acotinase
75
What enzyme turns a-D-Glucose-6-phospate to a-D-Fructose-6-phosphate | Isomerase
Phosphohexose Isomerase
76
What enzyme turns ATP + L-tyrosine + t-RNA to L-tyrosyl-tRNA + AMP + PP | Ligase
Tyrosine-tRNA synthetase
77
The 5 tetramers of lactate dehydrogenase
- M4 - M3H - M2H2 - MH3 - H4
77
Can exist in either of two states: R0 orT0
Dimeric Protein
78
Pyrrole-2-carboxylate mimics the planar transition state of what reaction?
L-Proline to D-Proline
79
The abzyme is then used to catalyze the reaction D-Alaninw + Pyridoxial 5'-P to Pyruvate + Pyridoxamine 5'-P
N^a-(5'-Phosphopyridoxyl)-L-lysine moiety (antigen)

biochem lec (10 decks)

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