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CLINICAL CHEM > Enzymes > Flashcards

Enzymes Flashcards

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1
Q

T or F: All enzymes are proteins but not all proteins are enzymes

A

T

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2
Q

how do enzymes speed up a rxn

A

they lower the activation energy

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3
Q

def? non-protein chemical compound that is bound tightly to an enzyme and is required for catalysis.

A

cofactor

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4
Q

are cofactors organic or inorganic

A

inorganic

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5
Q

are coenzymes organic or inorganic

A

organic

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6
Q

what is it called when a coenzyme is bound tightly to an enzyme

A

prothetic group

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7
Q

def? enzyme (apoenzyme) + COEnzyme (prothetic)

A

holoenzyme

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8
Q

t or F: The enzyme shifts the equilibrium of the reaction to the right.

A

F

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9
Q

T or F: The enzyme alters the equilibrium constant of the reaction.

A

F

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10
Q

T or F: The enzyme increases the rate of the reaction.

A

T

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11
Q

T or F: The enzyme alters the energy difference between reactants and products

A

F

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12
Q

if the substrate and inhibitor bind to the same place what kind of inhibition is this

A

competitive

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13
Q

T or F: A competitive inhibitor will alter the apparent Km of the reaction

A

T

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14
Q

T or F: An enzyme alters the Gibb’s free energy of the reaction.

A

F

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15
Q

T or F: Enzymes cause a reaction with a positive free energy to occur spontaneously.

A

F

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16
Q

T or F: An enzyme’s natural substrate has the highest Km.

A

F

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17
Q

what is used to measure enzymatic activity

A

spectrophotometric

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18
Q

what form of NADPH and NADH does UV light get absorbed

A

reduced

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19
Q

if an enzyme rxn does not result in a change in absorbance what can be used

A

coupled assay

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20
Q

an enzyme using NADH as a substrate can be assayed at what nm of light

A

340 nm

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21
Q

I unit of enzyme activity =

A

1 mol of molecules production / min

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22
Q

what is beers law

A

the absorbance of a sample is proportional to the concentration

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23
Q

what is lamberts law

A

the absorbance of a sample is proportional to the sample thickness

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24
Q

what is the formula for absorbance

A

= molar absorptivity x path length x conc

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25
Q

what is the fomula for conc

A

= (absorption x molar absorptivity x path length) dilution factor

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26
Q

what is measured in biological samples for diagnosis, prognosis, assessment of treatment, and monitoring the progression of the disease.

A

enzymes

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27
Q

what is the clinical significance of measuring ALP (alkaline phosphatase)

A

hepatic disorder

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28
Q

what is the clinical significance of measuring CK (creatine kinase) and LD (lactate dehydrogenase)

A

myocardial infarction

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29
Q

what cofactor does CK require

A

Mg 2+

30
Q

Creatine + ATP =

A

phosphocreatine

31
Q

where do you mostly find CK

A

skeletal muscles

32
Q

function of phosphocreatine

A

energy reservoir

33
Q

what tissue has CK-MM

A

skeletal

34
Q

what tissue has CK-MB

A

cardiac

35
Q

what tissue has CK-BB

A

brain

36
Q

which CK enzyme is the most specific marker of a heart attack

A

CK-MB

37
Q

what is a sensitive indicator of acute myocardial infarction and muscular dystrophy.

A

CK

38
Q

what kind of sample is needed for measuring CK

A

serum or heparinized plasma

39
Q

T or F: it is ok for a CK sample to be collected with EDTA, citrate, or oxalate

A

F

40
Q

_____ samples should be avoided with testing for CK

A

hemolyzed

41
Q

what tissues have LD-1

A

heart and RBC

42
Q

what tissues have LD-2

A

heart and RBC

43
Q

what tissue has LD-3

A

lungs

44
Q

what tissues have LD-4 and LD-5

A

liver and skeletal muscle

45
Q

which LD enzyme is usually the highest

A

LD-2

46
Q

A physician calls to request a CK on a sample already sent to the laboratory for coagulation studies. The sample is 4-hour-old citrated/EDTA blood and has been stored at 4oC. The plasma shows very slight hemolysis. What is the best course of action and the reason for it?

A

Reject the sample because the citrate/EDTA will interfere

47
Q

True or false? CK Highest levels are seen in Duchenne’s muscular dystrophy.

A

T

48
Q

T or F? Ck Levels are unaffected by strenuous exercise

A

F

49
Q

T or F? CK Levels are unaffected by repeated intramuscular injections

A

F

50
Q

t or f? The enzyme is highly specific for heart injury (CK)

A

F

51
Q

t or F? An LD-1:LD-2 ratio greater than 1.0 is specific evidence of AMI.

A

F

52
Q

t or F? Malignancy usually causes an increase in LD-2, LD-3, LD-4.

A

F

53
Q

T or F? LD-3 is normally the isoenzyme in highest concentration in serum.

A

F

54
Q

t or f? Hepatic injury is associated with increases in LD-4 and LD-5.

A

T

55
Q

what conditions will interfere with the measurement of LD?

A

Slight hemolysis during sample collection

56
Q

t or f? The formation of pyruvate from lactate (forward reaction) generates NAD1. (when measuring LD)

A

F

57
Q

t or F? The pyruvate to lactate reaction proceeds at about twice or 3 times the rate as the forward reaction. (when measuring LD)

A

T

58
Q

t or F? The lactate to pyruvate reaction is optimized at pH 7.4.
(when measuring LD)

A

F

59
Q

T or F: The lactate to pyruvate reaction is optimized at pH 8.4 (when measuring LD)

A

T

60
Q

t or F: when measuring LD the negative rate reaction is preferred.

A

F

61
Q

t or f (enzymatic rxn): NADH has absorbance maxima at 340 and 366nm.

A

T

62
Q

t or f (enzymatic rxn): Enzyme concentration must be in excess to achieve zero-order kinetics.

A

F

63
Q

t or f (enzymatic rxn): Rate is proportional to substrate concentration in a zero-order reaction.

A

F

64
Q

t or f (enzymatic rxn): Accumulation of the product increases the reaction rate.

A

F

65
Q

what is the coupling enzyme used in the kinetic AST reaction of Henry.

A

Malate dehydrogenase

66
Q

t or f: Hemolysis will cause positive interference in both AST and ALT assays.

A

T

67
Q

t or f: in the methods of Henry Loss of activity occurs if samples are frozen at -200C.

A

F

68
Q

t or f: in the method of Henry The absorbance at the start of the reaction should not exceed 1.0 A.

A

F

69
Q

t or F: in the method of Henry Reaction rates are unaffected by addition of P-5’-P to the substrate.

A

F

70
Q

T or F: amylase requires Ca2+ for full activity.

A

T

71
Q

what is the most sensitive marker for alcoholic liver disease.

A

g-Glutamyltransferase (GGT)

72
Q

what mineral do parathyroid hormone regulate

A

calcium, phosphorus and magnesium

CLINICAL CHEM (7 decks)

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