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Biochemistry LAB > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Enzymes Properties

A
  1. Almost all enzymes are proteins.
  2. They are heat labile.
  3. They are water-soluble.
  4. They can be precipitated
  5. They contain 16% weight as nitrogen
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2
Q

Almost all enzymes are proteins exception

A

ribozymes

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3
Q

few RNA molecules with enzymatic activity

A

ribozymes

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4
Q

enzymes are classified as

A

specialized proteins

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5
Q

They contain 16% weight as nitrogen because enzymes are made up of many

A

amino acids

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6
Q

Two general structural classes

A

Simple enzymes
Conjugated enzymes:

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7
Q

only of protein (amino acid chains)

A

Simple enzymes

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8
Q

nonprotein part + protein part

A

Conjugated enzymes

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9
Q

Parts of an enzyme molecule

A

Non-protein part
Protein part
Holoenzyme

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10
Q

Non-protein part

A

prosthetic group, cofactor or coenzyme

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11
Q

Protein part

A

apoenzyme

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12
Q

complete structure of apoenzyme and prosthetic group.

A

Holoenzyme:

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13
Q

enzymes that contain tightly bound metal ions are termed

A

metalloenzymes.

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14
Q

Prosthetic group examples

A

pyridoxal phosphate,
flavin mononucleotide (FMN),
flavin adenine dinucleotide (FAD),
thiamin pyrophosphate,
biotin,

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15
Q

tight, stable incorporation into a protein’s structure

A

Prosthetic group

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16
Q

bind in a transient, dissociable manner either to the enzyme or to a substrate such as ATP.

must be present/available in the medium surrounding the enzyme for catalysis to occur.

A

Cofactors

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17
Q

Enzymes that require a metal ion cofactor are termed

A

metal-activated enzymes

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18
Q

The most common cofactors also are

A

metal ions.

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19
Q

serve as substrate shuttles

A

Coenzymes

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20
Q

Coenzymes example

A

Dehydrogenases -Nicotinamide adenine dinucleotide

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21
Q

Specificity

A
  1. Absolute Specificity.
  2. Stereochemical Specificity.
  3. Group Specificity.
  4. Linkage Specificity
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22
Q

enzyme will catalyze (or speed up) a particular reaction for only one substrate.

A
  1. Absolute Specificity.
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23
Q

enzyme can distinguish between stereoisomers.

A

Stereochemical Specificity.

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24
Q

involves structurally similar compounds that have the same functional groups.

A

Group Specificity.

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25
Q

Group Specificity example

A

Carboxypeptidase

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26
Q

Stereochemical Specificity example

A

L-Amino-acid oxidase

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27
Q

Absolute Specificity example

A

Urease
glucose oxidase

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28
Q

Most general specificity Involves a particular type of bond, irrespective of the structural features in the vicinity of the bond.

A

Linkage Specificity

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29
Q

Linkage Specificity example

A

Phosphatases

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30
Q

takes the form of a cleft or pocket on the enzyme’s surface or, for some multimeric enzymes, at the interface between subunits.

A

The active site

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31
Q

The active site function

A
  1. provides a three-dimensional environment that both shields or protects substrates from solvent
  2. where a substrate binds with
  3. binds any cofactors and prosthetic groups that may be required for catalysis
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32
Q

substrate bind with the substrate-binding site

A

1st Substrate recognition site.
2nd Appropriate angle.
3rd Proximity.
4th Functional group.
5th Transition state complex.
6th Products.

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33
Q

Models for substrate binding

A

Lock-and-key model
Induced-fit model

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34
Q

Lock-and-key model proposed by

A

Fischer

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35
Q

active site already exists in proper conformation even in absence of substrate.

A

Lock-and-key model

36
Q

Induced-fit model proposed by

A

Koshland in 1963

37
Q

The substrate during its binding induces conformational changes in the active site to attain the final catalytic shape and form.

A

Induced-fit model

38
Q

Six classifications of enzymes

A
  1. Oxidoreductase.
  2. Transferases
  3. Hydrolases:
  4. Lyases
  5. Isomerases
  6. Ligases
39
Q

oxidoreductase requires a ________ that is ________ as the substrate is ________

A

coenzyme (a carrier) ; oxidized or reduced ; reduced or oxidized

40
Q

Oxidoreductase Examples:

A

alcohol dehydrogenase,
lactate dehydrogenase,
xanthine oxidase,
glutathione reductase,
glucose-6-phosphate dehydrogenase

41
Q

Alcohol + (NAD+) → Aldehyde + NADH + (H+)

A

Oxidoreductase; Alcohol dehydrogenase

42
Q

(IUB)

A

International Union of Biochemistry

43
Q

transfer of a functional group (except hydrogen) from one substrate to another

A

Transferases:

44
Q

Alcohol dehydrogenase; IUB name

A

Alcohol-NAD-oxidoreductase;

45
Q

transfer of an amino group from one molecule to another

A

transaminases

46
Q

transfer of a phosphate group from adenosine triphosphate (ATP) to give adenosine diphosphate (ADP) and a phosphorylated molecule

A

kinases

47
Q

Transferases Examples:

A

aspartate and alanine transaminase (AST/ALT),
hexokinase,
phosphoglucomutase,
hexose-1-phosphate uridyltransferase,
ornithine carbamoyl transferase,

48
Q

Hexose + ATP → Hexose-6-phosphate + ADP

A

Transferases; Hexokinase

49
Q

Hexokinase systematic name is

A

ATP-Hexose–6-phosphatetransferase

50
Q

bring about hydrolysis

A

Hydrolases

51
Q

hydrolyze ester, ether, peptide or glycosidic bonds by adding water and then breaking the bond

A

Hydrolases:

52
Q

breaking of glycosidic bonds in oligo- and polysaccharides

A

carbohydrases:

53
Q

breaking of peptide linkages in proteins,.

A

proteases:

54
Q

effect the breaking of ester linkages in triacylglycerols

A

lipases

55
Q

Hydrolases Examples:

A

glucose-6-phosphatase,
pepsin,
trypsin,
esterases,
glycoside hydrolases

56
Q

Acetyl choline + H2O → Choline + acetate

A

Hydrolases; or Acetyl choline hydrolase

57
Q

All ________ enzymes are hydrolases.

A

digestive

58
Q

removal of small molecule from a large substrate

A

Lyases

59
Q

remove groups from substrates or break bonds by mechanisms other than hydrolysis

A

Lyases

60
Q

effects the removal of the components of water from a double bond

A

dehydratase:

61
Q

effects the addition of the components of water to a double bond.

A

dehydratase:

61
Q

effects the addition of the components of water to a double bond.

A

hydratase:

62
Q

One of the product of dehydratase

A

Water

63
Q

Lyases Examples:

A

fumarase,
arginosuccinase,
histidine decarboxylase.

64
Q

Lyases reverse reaction

A

Synthase

65
Q

Fructose-1,6-bisphosphate → Glyceraldehyde-3-phosphate + dihydroxy acetone phosphate

A

Lyases; Aldolase

66
Q

isomerization of substrate

A

Isomerases

67
Q

produce optical, geometric or positional isomers of substrates. Catalyzes the isomerization of a substrate in a reaction, converting it into a molecule isomeric with itself.

A

Isomerases

68
Q

Isomerases Examples:

A

UDP-glucose,
epimerase,
retinal isomerase,
racemases,
triosephosphate isomerase.

69
Q

Glyceraldehyde-3-phosphate → Di-hydroxy-acetone-phosphate

A

Isomerases; Triose phosphate isomerase

70
Q

joining together two substrates

A

Ligases

71
Q

link two substrates together, usually with the simultaneous hydrolysis of ATP

A

Ligases

72
Q

Ligases examples

A

alanyl-t. RNA synthetase, glutamine synthetase, DNA ligases

73
Q

Acetyl CoA + CO2 + ATP → Malonyl CoA + ADP + Pi

A

Ligases; Acetyl CoA carboxylase

74
Q

Factors affecting enzymatic activity

A

Temperature
pH
Substrate concentration
Enzyme concentration
Concentration of the end-products
Inhibition

75
Q

temperature at which an enzyme exhibits maximum activity

A

Optimum temperature

76
Q

higher than the optimum temperature → more the atoms vibrate →

A

breaking of hydrogen bonds and
other forces

77
Q

The enzymatic activity is maximum at a particular pH which is called its

A

optimum pH.

78
Q

Each human enzyme has a characteristic optimum pH, which usually falls within the physiological pH
range of _______ (EXCEPT digestive enzymes).

A

7.0–7.5

79
Q

the rate equation for one substrate-enzyme catalyzed reaction.

A

Michaelis-Menten equation

80
Q

Non-substrate molecules → decrease in enzymatic activity

A

Inhibition

81
Q

active site or catalytic site of an enzyme is occupied by a substance other than the substrate → activity is inhibited

A

Competitive inhibition (Reversible)

82
Q

the inhibitor can be removed from its site of binding without affecting the activity of the enzyme. Attaches but not to the active site

A

Reversible-Non-competitive Inhibition

83
Q

the inhibitor can be removed only at the loss of enzymatic activity.

A

Irreversible Non-competitive Inhibition:

84
Q

enzyme is used for estimation of “true glucose” in blood and body fluids.

A

“Glucose oxidase”

85
Q

used for estimation of serum uric acid.

A

“uricase”

86
Q

used for estimation of urea in blood and body fluids.

A

“urease”

Biochemistry LAB (5 decks)

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