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Clinical Chemistry > Enzymology Introduction > Flashcards

Enzymology Introduction Flashcards

1
Q

How enzymes act in reactions

A

Lower activation energy for reactions

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2
Q

Where enzymes are found

A

In all body tissues, appear in serum after cellular injury

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3
Q

Enzyme specificity - absolute specificity

A

Combines with one substrate and catalyzes one reaction

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4
Q

Enzyme specificity - group specificity

A

Combines with substrates containing a particular chemical group

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5
Q

Enzyme specificity - bond or reaction specificity

A

Forms or breaks one type of covalent bond

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6
Q

Enzyme specificity - stereoisomeric/geometric specificity

A

Combines with only one optical or geometric isomer

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7
Q

Main function of enzymes

A

Accelerates biochemical reactions; biological catalyst

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8
Q

Enzyme involvement in reactions

A

Enzyme is not a direct participant and does not change

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9
Q

Binding sites of enzymes

A

Active site (main), Allosteric site (for cofactors)

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10
Q

Role of cofactors

A

Activate enzyme; reaction won’t proceed without them

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11
Q

Types of cofactors

A

Activator (inorganic), Coenzyme (organic)

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12
Q

Apoenzyme + Cofactor

A

Holoenzyme

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13
Q

Inactive form of enzyme

A

Proenzymes/Zymogens

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14
Q

Common enzymes with proenzymes

A

Hydrolases

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15
Q

Enzyme classification EC code 1

A

Oxidoreductases - Redox reaction (hydrogen and oxygen)

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16
Q

Function of oxidoreductases

A

Addition of hydrogen and oxygen; oxidation removes hydrogen, adding oxygen replaces hydrogen

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17
Q

Examples of oxidoreductases

A

Dehydrogenase, oxidase, hydrogenase, oxygenase

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18
Q

Enzyme classification EC code 2

A

Transferases - Transfers functional group (not H and O)

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19
Q

Function of transferases

A

Transfers functional groups like carbohydrate, phosphate, hydroxy group, amino acid

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20
Q

Example of transferase reaction

A

Creatine kinase + ATP <-> CP + ADP

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21
Q

Examples of transferases

A

Transferase, kinase (phosphate extraction from ATP), phosphorylase (transfers phosphate)

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22
Q

Enzyme classification EC code 3

A

Hydrolases - Removes functional group with water

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23
Q

Examples of hydrolases

A

Amylase (destroys glycosidic bonds), Lipase (destroys ester bonds), Trypsin/Chymotrypsin (destroys peptide bonds)

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24
Q

Enzyme classification EC code 4

A

Lyases - Removes functional group without water (H2O)

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25
Q

Function of lyases

A

Products have double bond

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26
Q

Examples of lyases

A

Aldolase, decarboxylase

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27
Q

Enzyme classification EC code 5

A

Isomerases - Converts isomer from one orientation to another

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28
Q

Example of isomerase reaction

A

D to L orientation of glucose

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29
Q

Identification of isomerases

A

Isomerase in name; Example - triose phosphate isomerase

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30
Q

Enzyme classification EC code 6

A

Ligases - Bond formation coupled with ATP hydrolysis

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31
Q

Example of ligase

A

Glutathione synthetase

32
Q

Enzyme kinetics concept

A

Substrate needs specific energy to proceed with a reaction, called activation energy

33
Q

Enzyme’s role in reaction

A

Enzyme reduces energy barrier, accelerates reaction

34
Q

Equilibrium in enzyme kinetics

A

Same result, faster reaction

35
Q

Effect of heat on enzyme reactions

A

Heat accelerates reactions by increasing molecular movement

36
Q

Enzyme kinetics reaction mechanism

A

Enzyme + Substrate <-> ES <-> Product + Enzyme (free again)

37
Q

Zero order kinetics

A

Enzyme < Substrate, rate is constant, enzyme becomes rate-limiting when active site is saturated

38
Q

First order kinetics

A

Enzyme > Substrate, rate is dependent on substrate concentration, increased substrate increases enzyme-substrate complex

39
Q

Rate limiting component in zero order kinetics

40
Q

Rate limiting component in first order kinetics

41
Q

Inhibitor type same structure as substrate, binds to active site, reversible

A

Competitive inhibitor:

42
Q

Inhibitor type Binds to enzyme (not active site), reversible, may destroy structure

A

Non-competitive inhibitor:

43
Q

Inhibitor type Binds to ES complex, increasing substrate concentration, no product formation

A

Uncompetitive inhibitor:

44
Q

Inhibitor type can bind to either substrate or enzyme

A

Mixed inhibitor:

45
Q

Michaelis-Menten equation

A

v = Vmax (S) / Km + (S)

46
Q

Lineweaver-Burke plot

A

Double reciprocal plot of Michaelis-Menten equation: y = mx + b

47
Q

Fixed-time/End point measurement

A

One-time measurement with stop solution (weak acid)

48
Q

Kinetic/Continuous measurement

A

Multiple measurements, checks actual activity and monitors linearity

49
Q

Measurement unit for enzyme activity

A

IU: Amount of enzyme that catalyzes 1 umol of substrate

50
Q

Measurement unit for enzyme concentration

51
Q

SI unit for enzyme activity

A

Katal: Number of moles per second (mol/sec)

52
Q

Conversion between IU and Katal

A

1 IU = 17 katals

53
Q

Conventional unit for enzyme activity

A

IU: Amount of enzyme that catalyzes 1 umol of substrate per minute

54
Q

SI unit for enzyme activity

A

Katal: Amount of enzyme that catalyzes 1 mol of substrate per second

55
Q

Conversion between IU and nkat

A

1 IU = 0.0161 ukat or 16.7 (17) nkat

56
Q

Conversion between IU and kat

A

1 kat = 6 x 10^7 IU

57
Q

Reactants combined, reaction proceeds for set time, reaction stopped, amount of reaction measured

A

Fixed-time endpoint method

58
Q

Multiple measurements of absorbance over time using a spectrophotometer

A

Continuous-monitoring kinetic method

59
Q

Factor affecting enzymatic reaction, pH range for most reactions

A

7.0-8.0 (except ACP: 4.5, ALP: 9-10)

60
Q

Effect of temperature on enzymatic reaction rate

A

Rate doubles for every 10°C increase

61
Q

Temperature range for denaturation in enzymatic reactions

62
Q

Incubation temperature deviation in enzyme assays

63
Q

Definition of cofactors

A

Nonprotein entities that bind to enzymes for reactions

64
Q

Activators as cofactors

A

Inorganic, metallic or non-metallic ions (e.g. Zn, Ca, Mg, Cl)

65
Q

Definition of coenzymes

A

Organic substances, serve as second substrates in enzymatic reactions

66
Q

Coenzymes bound tightly to enzymes

A

Prosthetic groups

67
Q

Example of coenzyme

A

NAD(P) for dehydrogenases, Pyridoxal PO4 for AST, ALT

68
Q

Effect of adding substrate in competitive inhibitor

A

Increased substrate reverses inhibition

69
Q

Effect of adding substrate in non-competitive inhibitor

70
Q

Effect of adding substrate in uncompetitive inhibitor

A

Increases inhibition

71
Q

Lineweaver-Burk plot in competitive inhibitor

A

Same Cmax, increased Km (rightward shift)

72
Q

Lineweaver-Burk plot in non-competitive inhibitor

A

Decreased Vmax, same Km

73
Q

Lineweaver-Burk plot in uncompetitive inhibitor

A

Decreased Vmax, decreased Km

74
Q

Macroenzyme definition

A

High-molecular-mass forms of serum enzymes bound to immunoglobulin or non-immunoglobulin substance

75
Q

Examples of enzymes with macroforms

A

CK, LD, ALT, AST, GGT, ACP, ALP, AMS, LPS

Clinical Chemistry (43 decks)

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