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Clinical Chemistry > Enzymes > Flashcards

Enzymes Flashcards

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1
Q

specific biologic proteins that catalyze biochemical reactions
without altering the equilibrium point of the reaction or being consumed or
changed in composition.

A

Enzymes

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2
Q

The different forms may be differentiated from each other based on
certain physical properties, such as electrophoretic mobility, solubility, or
resistance to inactivation.

A

isoenzyme

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3
Q

results when an enzyme is subject to posttranslational modifications.

A

isoform

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4
Q

a nonprotein molecule, called a

_____, may be necessary for enzyme activity.

A

cofactor

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5
Q

Inorganic cofactors, such as

chloride or magnesium ions, are called

A

activators.

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6
Q

is an organic

cofactor, such as nicotinamide adenine dinucleotide (NAD).

A

coenzyme

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7
Q

When bound tightly

to the enzyme, the coenzyme is called a

A

prosthetic group.

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8
Q

The enzyme portion ______, with its respective coenzyme, forms a complete and active
system, a ______.

A

apoenzyme; holoenzyme

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9
Q

Catalyze an oxidation–reduction reaction between two

substrates

A

Oxidoreductases.

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10
Q

Catalyze the transfer of a group other than hydrogen from

one substrate to another

A

Transferases.

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11
Q

Catalyze hydrolysis of various bonds

A

Hydrolases.

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12
Q

Catalyze removal of groups from substrates without hydrolysis; the
product contains double bonds

A

Lyases.

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13
Q

Catalyze the interconversion of geometric, optical, or

positional isomers

A

Isomerases.

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14
Q

Catalyze the joining of two substrate molecules, coupled with
breaking of the pyrophosphate bond in adenosine triphosphate (ATP) or a
similar compound

A

Ligases.

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15
Q

The excess energy, called
_________, is the energy required to raise all molecules in 1 mole of a
compound at a certain temperature to the transition state at the peak of the
energy barrier.

A

activation energy

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16
Q

refers to enzymes that predominantly combine

with only one optical isomer of a certain compound.

A

Stereoisomeric specificity

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17
Q

the reaction rate is

directly proportional to substrate concentration.

A

first-order kinetics

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18
Q

the reaction rate depends only on enzyme

concentration.

A

zero-order kinetics

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19
Q

is the substrate concentration at which

the reaction velocity is half of the maximum level.

A

Michaelis-Menten constant (Km)

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20
Q

more accurate and convenient
determination of Vmax and Km may be made through a ____________, a
double-reciprocal plot of the Michaelis-Menten constant,

A

Lineweaver-Burk plot

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21
Q

For each __ degree increase in temperature, the rate

of the reaction will approximately double

A

10

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22
Q

The rate of denaturation increases as the temperature

increases and is usually significant at

A

40°C to 50°C.

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23
Q

physically bind to

the active site of an enzyme and compete with the substrate for the active site.

A

Competitive inhibitors

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24
Q

binds an enzyme at a place other than the active
site and may be reversible in the respect that some naturally present metabolic
substances combine reversibly with certain enzymes.

A

noncompetitive inhibitor

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25
Q

the inhibitor
binds to the ES complex—increasing substrate concentration results in more ES
complexes to which the inhibitor binds and, thereby, increases the inhibition.

A

Uncompetitive inhibition

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26
Q

has the ability to bind to either the E or ES complex at a different site
from the substrate active site.

A

mixed

inhibitor

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27
Q

Vmax

unaltered; Km appears increased.

A

Competitive inhibition

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28
Q

Vmax decreased;

Km unchanged.

A

Noncompetitive inhibition

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29
Q

Vmax decreased; Km appears

decreased.

A

Uncompetitive inhibition

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30
Q

a convenient method of

enzyme quantitation is measurement of

A

catalytic activity.

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31
Q

One of two general methods may be used to measure the extent of an
enzymatic reaction:

A

fixed-time and continuous-monitoring or kinetic assay

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32
Q

the reactants are combined, the reaction
proceeds for a designated time, the reaction is stopped (usually by inactivating
the enzyme with a weak acid), and a measurement is made of the amount of
reaction that has occurred.

A

fixed-time method,

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33
Q

multiple measurements, usually
of absorbance change, are made during the reaction, either at specific time

intervals (usually every 30 or 60 seconds) or continuously by a continuous-
recording spectrophotometer.

A

continuous-monitoring or kinetic assays,

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34
Q

the amount of enzyme that will catalyze the reaction of 1 μmol of
substrate per minute under specified conditions of temperature, pH, substrates,
and activators.

A 
international
unit (IU)
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35
Q

specific. Enzyme concentration is
usually expressed in units per liter (IU/L). The unit of enzyme activity
recognized by the International System of Units (Système International d’Unités
[SI]) is the

A

katal (mol/s).

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36
Q

are chemically bonded to adsorbents, such as agarose

or certain types of cellulose, by azide groups, diazo, and triazine.

A

Immobilized enzymes

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37
Q

widely distributed in tissue, with highest activities found in skeletal
muscle, heart muscle, and brain tissue.

A

CK

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38
Q

Total serum CK levels have also been used as an early diagnostic tool to identify
patients with_____ infections.

A

Vibrio vulnificus

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39
Q

useful in the diagnosis of ectopic pregnancies.

A

and

CK/progesterone ratio

40
Q

The major isoenzyme in the sera of healthy people is the

A

MM form.

41
Q

<6% of total CK

A

CK-MB

42
Q

atypical forms are

generally of two types (CK)

A

macro-CK and mitochondrial CK.

43
Q

appears to migrate to a position midway between CK-MM and
CK-MB. comprises CK-BB complexed with
immunoglobulin.

A

macro-CK

44
Q

bound to the exterior surface of the inner
mitochondrial membranes of muscle, brain, and liver. It migrates to a point
cathodal to CK-MM and exists as a dimeric molecule of two identical subunits.

A

Mitochondrial CK (CK-Mi)

45
Q

is an enzyme released from
erythrocytes in hemolyzed samples and appearing as a band cathodal to CK-
MM.

A

adenylate kinase (AK).

46
Q

the most

commonly performed method in the clinical laboratory for CK

A

Oliver-Rosalki (reverse method)

47
Q

enzyme that catalyzes the interconversion of lactic and pyruvic acids.

A

Lactate Dehydrogenase

48
Q

occur most frequently with pulmonary

involvement and are also observed in patients with various carcinomas.

A

Elevations of LDH-3

49
Q

isoenzymes are found primarily in liver and skeletal muscle

tissue

A

LDH-4 and LDH-5

50
Q

functions as a coenzyme in SGOT/SGPT

A

Pyridoxal phosphate (B6)

51
Q

Half-life of AST

A

16hrs

52
Q

Half-life of ALT

A

24hrs

53
Q

belongs to a group of enzymes that catalyze the hydrolysis of various
phosphomonoesters at an alkaline pH.

A

Alkaline Phosphatase

54
Q

ALP requires ___ as an activator

A

Mg2+

55
Q

Migration pattern of ALP: fastest to slowest

A

Liver
Bone
Placental
Intestine

56
Q

Most heat stable to heat labile

A

Placental
Intestinal
Liver
Bone

57
Q

Placental ALP will resist heat denaturation at

A

65°C for 30 minutes.

58
Q

ALP activity is measured

before and after heating the serum at

A

56°C for 10mins

59
Q

The most frequently seen are the Regan

and Nagao isoenzymes. They have been referred to as

A

carcinoplacental alkaline

phosphatases

60
Q

migrates to the same position as the bone fraction and
is the most heat stable of all ALP isoenzymes, resisting denaturation at 65°C for
30 minutes. Its activity is inhibited by phenylalanine.

A

Regan isoenzyme

61
Q

may be considered a variant of the Regan isoenzyme.
Its electrophoretic, heat stability, and phenylalanine inhibition properties are
identical to those of the Regan fraction.

A

Nagao isoenzyme

62
Q

Nagao also can be inhibited by

A

L-leucine

63
Q

A continuous monitoring
technique based on a method devised by _______ allows
calculation of ALP activity based on the molar absorptivity of p-nitrophenol.

A

Bowers and McComb

64
Q

ALP Activity in serum increases approximately _____ on standing at 25°C or 4°C for several hours.

A

3%

to 10%

65
Q

ALP Values

may be ___ higher following ingestion of a high-fat meal.

A

25%

66
Q

3 approaches to identify ALP isoenzymes

A

Electrophoresis
Heat Inactivation
Chemical inhibition

67
Q

One of the most specific substrates for prostatic ACP is

A

thymolphthalein

monophosphate.

68
Q

Chemical inhibition methods used to differentiate the prostatic
portion most frequently use ____ as the inhibitor.

A

tartrate

69
Q

Vaginal washings are examined for seminal fluid–ACP

activity, which can persist for up to __ days

A

4

70
Q

includes incubation with an antibody to

prostatic ACP followed by washing and incubation with p-nitrophenylphosphate.

A

immunoenzymatic assay (Tandem E)

71
Q

Serum activity decreases within
____ if the sample is left at room temperature without the addition of a
preservative.

A

1 to 2 hours

72
Q

If not assayed immediately, serum should

be

A

frozen or acidified (<6.5)

73
Q

involved in peptide and protein synthesis,
regulation of tissue glutathione levels, and the transport of amino acids across
cell membranes.

A

GGT

74
Q

GGT levels will be increased in patients receiving enzyme-

inducing drugs such as

A

warfarin, phenobarbital, and phenytoin.

75
Q

TRUE/FALSE: GGT Levels usually return to normal within 2 to 3 weeks
after cessation but can rise again if alcohol consumption is resumed.

A

TRUE

76
Q

most widely accepted substrate for use in GGT analysis is

A

γ-glutamyl-p-

nitroanilide.

77
Q

TRUE/FALSE: Hemolysis
does not interfere with GGT levels because the enzyme is lacking in
erythrocytes.

A

TRUE

78
Q 
an enzyme belonging to the class of hydrolases that catalyze
the breakdown of starch and glycogen.
A

Amylase (AMY)

79
Q

condition that results when the AMY molecule combines
with immunoglobulins to form a complex that is too large to be filtered across
the glomerulus.

A

Macroamylasemia

80
Q

2 major bands of amylase

A

P-type and S-type isoamylase

81
Q

derived from pancreatic tissue;

A

P isoamylase

82
Q

derived from salivary gland tissue, as well as the fallopian tube
and lung.

A

S isoamylase

83
Q

TRUE/FALSE: The isoenzymes of salivary origin (S1, S2, S3) migrate most quickly,
whereas those of pancreatic origin (P1, P2, P3) are slower.

A

TRUE

84
Q

The most commonly observed fractions of amylase are

A

P2, S1, and S2.

85
Q

Amylase methodologies: Measures the disappearance of starch substrate

A

Amyloclastic

86
Q

Amylase methodologies: Measures the appearance of the product

A

Saccharogenic

87
Q

Amylase methodologies: Measures the increasing color from production of product coupled with a chromogenic dye

A

Chromogenic

88
Q

Amylase methodologies: Coupling of several enzyme systems to monitor amylase activity

A

Continuous monitoring

89
Q

TRUE/FALSE: plasma triglycerides
suppress or inhibit serum AMY activity, AMY values may be normal in acute
pancreatitis with hyperlipemia.

A

TRUE

90
Q

enzyme that hydrolyzes the ester linkages of fats to produce

alcohols and fatty acids.

A

Lipase (LPS)

91
Q

used an olive oil substrate and measured the liberated fatty acids by
titration after a 24-hour incubation.

A

Cherry-Crandall

method

92
Q

an oxidoreductase that
catalyzes the oxidation of glucose-6-phosphate to 6-phosphogluconate or the

corresponding lactone.

A

Glucose-6-phosphate dehydrogenase (G-6-PD)

93
Q

ACP,

ALP, ALT, amylase, AST, CK, GGT, LDH, lipase

A

Macroenzymes

94
Q

are high-molecular-mass forms of the serum enzymes that can be bound to either an immunoglobulin (macroenzyme type 1) or a nonimmunoglobulin substance
(macroenzyme type 2).

A

Macroenzymes

95
Q

superfamily of isoenzymes that are involved in the

metabolism of more than 50% of all drugs.

A

450 enzymes

Clinical Chemistry (9 decks)

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