Clin Chem (2) Exam 1

When a reaction is performed in zero-order kinetics:
The rate of the reaction is independent of the substrate concentration
The substrate concentration is very low
The enzyme level is always high
The rate of reaction is directly proportional to the substrate concentration

The rate of the reaction is independent of the substrate concentration

Activation energy is:
Increased by enzymes
The energy needed for an enzyme reaction to stop
Very high in catalyzed reactions
Decreased by enzymes

Decreased by enzymes

Examples of cofactors include
pyridoxal phosphate and coenzyme A
Zn+2, Mg+2, and Ni+2
biotin and thiamine pyrophosphate
b and c
a, b, and c

a, b, and c

Enzyme reaction rates are increased by increasing temperatures until they reach the point of
denaturation at:
100C
37C
25-35 C
40-60C

40-60C

Which of the following is true?
Enzymes alter the equilibrium of the reaction
Enzymes alter the standard free energy of the reaction
Enzymes force reactions to proceed in only one direction
All of the above
None of the above

None of the above

Which of the following is necessary for maximal enzyme velocity?
The enzyme concentration must be in excess of the substrate concentration.
The substrate concentration must be in excess of the enzyme concentration.
The substrate and enzyme concentrations must be equal.
The enzyme and substrate reaction must be reversible.

The substrate concentration must be in excess of the enzyme concentration.

What substrate concentration is typically utilized in enzymatic analyses to ensure zero-order kinetics?
substrate concentration of 10 – 100 X Km
substrate concentration of less than 10 X Km
substrate concentration equal to Km
substrate concentration equal to Km

substrate concentration of 10 – 100 X Km

A convenient method for assaying enzyme activity is based on measuring the conversion between the oxidized and reduced forms of nicotinamide adenine dinucleotide (NAD/NADH). Which form of nicotinamide adenine dinucleotide has a unique wavelength of absorption, and what is the wavelength at which is unique absorption is at its maximum?
Oxidized, 260 nm
Reduced, 340 nm
Reduced, 260 nm
Oxidized, 340 nm

Reduced, 340 nm

When substrate concentration is much greater than KM, the rate of catalysis is almost equal to
Vmax
kcat
Kd
All of the above
None of the above

Vmax

Activity of enzymes in plasma may be determined rather than concentration because:
The temperature is too high
There is not enough substrate
The amount of enzyme is too low to measure
The amount of enzyme is too high to measure

The amount of enzyme is too low to measure

Which CK isoenzyme is elevated in muscle diseases?
CK-MM
CK-BB
CK-MB
CK-NN

CK-MM

Elevation of serum amylase and lipase is commonly seen in:
Acid reflux disease
Acute pancreatitis
Acute appendicitis
Gallbladder disease

Acute pancreatitis

What type(s) of inhibition can be reversed?
Mixed
Noncompetitive
Competitive
All of the above
None of the above

All of the above

One of the enzymes involved in glycolysis, aldolase, requires Zn2+ for catalysis. Under conditions of zinc deficiency, when the enzyme may lack zinc, it would be referred to as the:
coenzyme
apoenzyme
substrate
holoenzyme
prosthetic group

apoenzyme

Vmax for an enzyme-catalyzed reaction
is unchanged in the presence of a uncompetitive inhibitor.
generally increases when pH increases.
is limited only by the amount of substrate supplied.
increases in the presence of a competitive inhibitor.
is twice the rate observed when the concentration of substrate is equal to the Km.

is twice the rate observed when the concentration of substrate is equal to the Km.

A physician orders several laboratory tests on a 55-year-old male patient who is complaining of generalized (all-over) pain, stiffness, fatigue, and headaches. Based on the following serum test results, what is the most likely diagnosis: ALP— significantly increased, GGT— normal?
Cirrhosis
Bone disease
Biliary obstruction
Primary metastatic cancer

Bone disease

Which is the most sensitive enzyme for monitoring chronic alcoholic liver disease?
NTP
ALP
GGT
AST

GGT

The recommended assay, because of its specificity and sensitivity for the measurement of the activity of the CK-MB isoenzyme, is the:
immunoinhibition assay
polyclonal competitive binding immunoassay
monoclonal sandwich immunoassay
isoenzyme electrophoresis.

monoclonal sandwich immunoassay

The usefulness of analyzing lipoprotein-associated phospholipase A2 for the identification of individuals at risk for future cardiovascular events is because of its:
upregulation in atherosclerotic lesions, particularly complex plaque
ability to transform stable coronary artery plaques to unstable ones
release of granules that destabilize complex plaque
release during inflammatory events such as coronary artery blockage

upregulation in atherosclerotic lesions, particularly complex plaque

Which of the following products are formed from the forward reaction catalyzed by ALT?
Alanine and alpha ketoglutarate
Oxaloacetate and glutamate
Pyruvate and glutamate
Aspartate and alanine

Pyruvate and glutamate

The major cellular origin of acid phosphatase activity in serum is:
Pancreas
Bone
Prostate
Liver

Prostate

Which of the following methods of measuring enzyme activity utilizes an increase in absorbance at 340 nm as an indicator reaction?
ALT(GPT) reaction
"Reverse" LD reaction
AST (GOT) reaction
"Forward" LD reaction

"Forward" LD reaction

Which of the following enzymes has multiple molecular forms (isoenzymes) whose clinical significance is used in diagnosis?
Creatine kinase
Alkaline phosphatase
Lactate dehydrogenase
Lactate dehydrogenase and creatine kinase only
Lactate dehydrogenase, creatine kinase, and alkaline phosphatase

Lactate dehydrogenase, creatine kinase, and alkaline phosphatase

One extracellular enzyme whose serum activity is measured clinically is:
Lactate dehydrogenase
Creatine kinase
Alkaline phosphate
Amylase

Amylase

If you were asked by your laboratory director to set up an enzyme profile (group of tests) specifically to assess hepatobiliary (biliary obstruction) disease, which one of the following sets of enzymes would be most appropriate?
LD, CK, ALT, AST
NTP, ALP, and 0-glutamyltransferase (GGT)
ALP, GGT, and CK
CHE, NTP, and CK

NTP, ALP, and 0-glutamyltransferase (GGT)

Activators that are required for normal CK activity include:
magnesium, manganese, and cobalt
NAD and NADH
magnesium only
pyroxidal phosphate and magnesium.

magnesium only

Which of the following enzymes detects very early changes in liver cell damage?
SGPT
ALT
ALP
GGT

GGT

Which of the following enzyme tests is most affected by "hemolysis?
Creatine kinase
Gamma glutamyl transferase
Alkaline phosphatase
Lactate dehydrogenase

Lactate dehydrogenase

Heart tissue contains which of the following CK isoenzymes?
MM and MB
MB only
BB only
MM only

MM and MB

Why is heparin the only acceptable anticoagulant to use when obtaining blood samples for ALP analysis?
Heparin maintains the integrity of the ALP molecule through freeze-thaw cycles
Other anticoagulants bind ALP and reduce its ability to react with substrate in enzyme reactions.
Heparin contains necessary cofactors for ALP to reach full enzyme activity.
Other anticoagulants contain inhibitors of magnesium, which is a required cofactor for ALP activation.

Other anticoagulants contain inhibitors of magnesium, which is a required cofactor for ALP activation.

Which of the following enzymes requires chloride (Cl-) as an activator?
Gamma glutamyl transferase GGT
Cholinesterase
Amylase
Lipase

Amylase

The enzyme that is inhibited by hemoglobin is:
Alkaline phosphatase
Lipase
Creatine kinase
Cholinesterase

Lipase

Of the following, the only clinically analyzed enzyme in the urine is:
Alanine transferase
Acid phosphatase
Cholinesterase
Amylase

Amylase

Which one of the following enzymes catalyzes the transfer of an amino group to alpha- ketoglutarate with the formation of oxaloacetate and glutamate?
Aspartate aminotransferase (AST)
Alanine aminotransferase (ALT)
5'-Nucleotidase (NTP)
Alkaline phosphatase (ALP)

Aspartate aminotransferase (AST)

A reaction rate assay measures enzyme _______ ; an endpoint assay measures enzyme ______
Concentration; activity
Activity; concentration
Concentration; concentration
Activity; activity

Activity; activity

Which of the following factors that influence enzymatic activity demonstrate a bell-shaped curve when relating the factor to enzyme activity?
Temperature
pH
Noncompetitive inhibitors
Both a and b

Both a and b

The principal source of serum cholinesterase (CHE) in blood is:
Pancreas
Bone
Skeletal muscle
Liver

Liver

Tartrate-resistant acid phosphatase (TR-ACP) that is present in unhemolyzed serum is synthesized mainly in:
Osteoclasts
Erythrocytes
Cells of the prostate gland
Hepatocytes

Osteoclasts

Increased enzyme activity is typically observed in serum or plasma:
only following mitochondrial damage.
only if a genetic abnormality is present.
following injury or damage to tissue.
only if hepatic damage has occurred.

following injury or damage to tissue.

Elevation of tissue enzymes in plasma may be used to detect:
Tissue necrosis or damage
Infectious diseases
Inflammation
Diabetes mellitus

Tissue necrosis or damage

What is the most sensitive enzyme to detect liver damage from chronic alcoholism?
Aspartate aminotransferase
Gamma-glutamyl transferase
Alkaline phosphatase
Alanine aminotransferase

Gamma-glutamyl transferase

When a myocardial infarction occurs, what is the first enzyme to reach peak elevation?
AST
Troponin
LD
CK

CK

Aspartate aminotransferase and alanine aminotransferase are both elevated in which of the following diseases?
Obstructive liver disease
Acute viral hepatitis
Muscular dystrophy
Myocardial infarction

Acute viral hepatitis

Increased lactate dehydrogenase activity, specifically LD4 and LD5, is associated with which of the following conditions?
Hemolytic anemia
Pernicious anemia
Acute viral hepatitis
Myocardial infarction

Acute viral hepatitis

In ion-exchange chromatography, solute mixtures are separated by virtue of the:
Partition coefficient between the two liquids
Steric exclusion based on pore sizes of the column
Magnitude and charge of ionic species
Hydrophilic beads of cross-linked dextran

Magnitude and charge of ionic species

Which one of the following statements concerning nephelometry is correct?
In a nephelometric measurement, light blocked by solutes in the solution at 180° from the incident light is measured by a photodetector.
Nephelometry is the measure of the concentration of particles by measuring the amount of incident light blocked by the particles.
In a nephelometric procedure, the measurement of scattered light that is not in the direct path of the transmitted light is made at right angles to the incident light.
The decrease in the intensity of scattered light is directly proportional to the number of particles in the solution, and the measurement of this decrease is called nephelometry.

In a nephelometric procedure, the measurement of scattered light that is not in the direct path of the transmitted light is made at right angles to the incident light.

In the clinical toxicology laboratory, it is common to use ______ to measure drugs of abuse.
Thin-layer chromatography
Gas chromatography coupled mass spectrometer
Electrophoresis
Atomic absorption

Gas chromatography coupled mass spectrometer

The term isocratic is used in high-performance liquid chromatography (HPLC) to mean that the:
Stationary phase is equilibrated with the mobile phase
Mobile phase consists of a constant solvent composition
Mobile phase is at constant temperature
Flow rate of the mobile phase is regulated

Mobile phase consists of a constant solvent composition

The most commonly used detector for clinical gas–liquid chromatography (GLC) is based on:
Flame ionization
Thermal conductance
Refractive index
UV light absorbance at 254 nm

Flame ionization

Because of the ability to identify and quantify proteins in a complex mixture, mass spectrometry combined with separation methods is an excellent analytical tool used specifically in the field of:
inborn errors of metabolism
proteomics
genomic research
trace metal analysis

proteomics

Mass spectrometry identifies analytes based on:
Molecular weight
Mass-to-charge ratio
Density of the band
Retention factor

Mass-to-charge ratio

In regard to mass spectrometry, what is a molecular ion?
It is the ion with the highest abundance in the mass spectrum of a compound
It is the sum of all ions produced displayed as a function of time
It is a component of a compound in solution
It is the unfragmented ion of the original molecule being studied

It is the unfragmented ion of the original molecule being studied

The soft ionization technique that uses a UV-absorbing compound upon which the analyte of interest is placed and eventually vaporized into a plume of ions directed into the mass analyzer is:
matrix-assisted laser desorption ionization
inductively coupled plasma ionization
electrospray ionization
atmospheric pressure photoionization

matrix-assisted laser desorption ionization

In a fluorometric measurement, the difference between the maximum wavelength of the excitation light and the maximum wavelength of the emitted fluorescence light is a constant referred to as:
polarization
the Stokes shift
chemiluminescence
Beer law

the Stokes shift

In which one of the following mass spectrometers does the fragmentation of ions take place after they have been separated by their m/z (mass/charge) value in a first stage?
In a tandem mass spectrometer
In a mass spectrometer interfaced with a gas chromatograph
In a quadrupole-trapping spectrometer
In an inductively coupled plasma mass spectrometer

In a tandem mass spectrometer

Which instrument requires a primary and secondary monochromator?
Atomic absorption spectrophotometer.
Fluorometer
Nephelometer
Spectrophotometer

Fluorometer

Which of the following statements about fluorometry is accurate?
Unsaturated cyclic molecules are often fluorescent
Fluorometry is less sensitive than spectrophotometry
Fluorescence is directly proportional to temperature
Fluorometry is less specific than spectrophotometry

Unsaturated cyclic molecules are often fluorescent

The polarization of light in fluorescent polarization immunoassay allows the measurement of which of the following?
Bound fraction in the presence of the free fraction
Only the bound fraction after the free fraction is removed
Both bound and free fractions
Antibodies to fluorescent label

Bound fraction in the presence of the free fraction

Which substance is used to generate the light signal in electrochemiluminescence?
Dioxetane phosphate
Luminol
Acridinium
Ruthenium

Ruthenium

A measure of peak separation in a chromatographic method that equals the difference in retention time for two components divided by the average of their peak widths is the definition of:
Affinity
Resolution
Retention factor
Derivatization

Resolution

A linear relationship between concentration and fluorescence intensity is seen as long as solutions being quantified have an absorbance of:
greater than .500
less than .500
greater than 1.000
less than .100

less than .100

_________ techniques measure light scattered by a particulate solution, and _______ techniques measure a decrease in light transmission through a particulate solution. ______ measurements can be performed on a basic UV/Visible spectrophotometer
turbidimetric, nephelometric, nephelometric
turbidimetric, nephelometric, turbidimetric
nephelometric, turbidimetric, nephelometric
nephelometric, turbidimetric, turbidimetric

nephelometric, turbidimetric, turbidimetric

A nanometer is equivalent to:
10^9 meters
10^-9 meters
One-ninth of a meter
Nine meters

10^ -9 meters

Turbidimetry is the measurement of the reduction in light transmission caused by:
Particle formation
Increase in excitation photon energy
Chelation of metals
Slowing of the spin rotation of electrons

Particle formation

Which of the following set of wavelengths is most representative of the visible region?
Greater than 950 nm
190-350 nm
350-750 nm
600-950 nm

350-750 nm

What component is used to isolate a wavelength in a spectrophotometer?
Light source
Readout
Photodetector
Monochromator

Monochromator

Which of the following analytic techniques separates molecules according to their mass-to-charge ratio?
High performance liquid chromatography
Mass spectrometry
Ion-selective electrodes
Isoelectric focusing

Mass spectrometry

Which of the following set of wavelengths is most representative of the visible light region?
600-750 nm
400-700 nm
150-400 nm
750-950 nm

400-700 nm

Which of the following equations represents Beer’s law?
E = hv
%T = 1/10 x 100
A = ε × b × c
ε = ΔpH × 0.59 V

A = ε × b × c

Which of the following correctly ranks electromagnetic radiation from low energy to high energy?
UV, visible, infrared, microwaves, x-rays, cosmic, gamma
Cosmic, gamma, x-rays, UV, visible, infrared, microwaves
UV, visible, infrared, cosmic, gamma, microwaves, x-rays
Microwaves, infrared, visible, UV, x-rays, gamma, cosmic

Microwaves, infrared, visible, UV, x-rays, gamma, cosmic

What is the purpose of a monochromator?
To process electrical signals into absorbance readings
To isolate a single wavelength or band of wavelengths of light
To emit a steady stream of radiant energy
To detect photons passing through a sample cell

To isolate a single wavelength or band of wavelengths of light

Which of the following is true concerning fluorometry?
All compounds undergo fluorescence
Emission wavelengths are always shorter than excitation wavelengths
The detector is always placed at a 70° angle to the excitation beam
Fluorescence is an inherently more sensitive technique than absorption

Fluorescence is an inherently more sensitive technique than absorption

Which of the following is true of chemiluminescence
Tungsten lamps are usually used as light sources for chemiluminescence assays
Energy is absorbed at one wavelength and then emitted at a lower wavelength
Light is emitted by molecules in excited states produced by chemical reactions
Chemiluminescence detectors measure absorbance at characteristic wavelengths

Light is emitted by molecules in excited states produced by chemical reactions

Mass spectrometry identifies analytes based on
Retention factor
Solubility in the mobile phase
Density of the band
Mass-to-charge ratio

Mass-to-charge ratio

Which one of the following cardiac biomarkers is elevated about 50 times the upper limit of normal at 24 hours after onset of an acute myocardial infarction?
Total CK
CK-2 (CKMB)
Troponin
Myoglobin

Troponin

Why would high-sensitivity C-reactive protein (CRP) be an indicator of a potential myocardial infarction?
It is an acute phase reactant plasma protein that rises in response to inflammation and the atherosclerotic process
It is an enzyme found in skeletal muscle and cardiac muscle that is released upon muscle damage
CRP levels rise in response to decreased ATP generation in the heart
It is a myocardial protein that regulates muscle contraction through interaction with myosin and actin

It is an acute phase reactant plasma protein that rises in response to inflammation and the atherosclerotic process

In which of the following disorders is measurement of brain type natriuretic peptide (BNP clinically useful?
Congestive heart failure
Tachycardia
Pericarditis
Acute myocardial infarctions (AMIs)

Congestive heart failure

Myoglobin is a good cardiac marker because it:
Is an extremely large protein and therefore does not diffuse into the blood very easily
Diffuses into the blood more slowly than CK-MB
Diffuses into the blood more quickly than CK-MB
Doesn't diffuse into the blood at all when cardiac tissue dies

Diffuses into the blood more quickly than CK-MB

The troponin complex consists of which of the following?
Troponin A, troponin C, and troponin T
Troponin M1, troponin M2, and troponin K
Troponin M and troponin H
Troponin T, troponin I, and troponin C

Troponin T, troponin I, and troponin C

Which one of the following is considered to be the most specific marker for adverse ventricular remodeling following an acute myocardial infarction?
Myoglobin
CK-2
Brain natriuretic peptide (BNP)
Troponin

Brain natriuretic peptide (BNP)

Which one of the following cardiac markers is elevated for the longest period of time after a myocardial infarction?
Troponins
CK-2 (CK-MB)
hs-CRP
Myoglobin

Troponins

Which one of the following specimen types and collection methods is best for laboratory assessment of brain natriuretic peptide (BNP) in the evaluation of congestive heart failure?
Serum in glass blood collection tubes only
EDTA-anticoagulated whole blood or plasma in plastic blood collection tubes only
Urine in sterile collection container for analysis of BNP metabolites only
Heparinized plasma in any type of blood collection tube

EDTA-anticoagulated whole blood or plasma in plastic blood collection tubes only

Laboratory measurements for brain natriuretic peptide (BNP) be reported in:
picomoles/milliliter
nanograms/liter
grams/deciliter
millimoles/liter

nanograms/liter

A cardiac marker that increases progressively with increasing severity of disease and is not increased (or decreased) in conditions that mimic congestive heart failure is:
myoglobin
B-type natriuretic peptide
troponin I
CK-2

B-type natriuretic peptide

The most common laboratory method used to assess brain natriuretic peptides is:
nephelometry
serum electrophoresis
immunoassay
HPLC

immunoassay

In a point-of-care (POC) test for a cardiac biomarker used in the evaluation of an individual with possible acute coronary syndrome, which one of the following is a Laboratory Medicine Practice guideline of the National Academy of Clinical Biochemistry (NACB)?
POC testing must be performed with a maximum turnaround time of 24 hours.
Laboratories that use qualitative POC biomarker assays should confirm results with a quantitative biomarker test.
Quality control and quality assurance are not required when using POC assays.
POC assays should provide quantitative results.

POC assays should provide quantitative results.

Chest pain that is associated with a decrease in oxygen supply to the heart muscle but that exhibits no cellular necrosis based on cardiac troponin value and is considered a less severe event is referred to as:
thrombolysis
congestive heart failure
acute myocardial infarction
angina

angina

The protein in cardiac muscle fibers that regulates contraction is?
troponin
actin
myosin
B-type natriuretic peptide

troponin

In your clinical chemistry laboratory, you use an immunoassay to detect blood levels of NT-proBNP. You receive a filled green-top anticoagulant-containing plastic blood collection tube with a request for NT-proBNP. What is your next step?
Because this is an incorrect specimen type, contact the physician/nurse immediately and request a serum specimen.
Proceed, because this tube contains heparin and provides plasma after centrifugation, which is acceptable for the NT-proBNP assay.
Because only whole blood is acceptable, go ahead and run the test on the green-top tube.
Proceed, because this tube will provide serum after centrifugation, which is acceptable for the NT-proBNP assay.

Proceed, because this tube contains heparin and provides plasma after centrifugation, which is acceptable for the NT-proBNP assay.

What are the laboratory results for CK-MB and cardiac troponin in the following conditions: muscular dystrophy, polymyositis, and extreme physical activity?
CK-MB normal, troponin normal
CK-MB normal, troponin elevated
CK-MB elevated, troponin elevated
CK-MB elevated, troponin normal

CK-MB elevated, troponin normal

Regarding assessment of congestive heart failure, NT-proBNP can be measured. This protein is:
an isoenzyme that migrates separately from BNP on an electrophoresis
the N-terminal fragment of pro-BNP
the C-terminal portion of the prepro-hormone natriuretic peptide (BNP)
degraded by circulating proteases to form the final form of BNP

the N-terminal fragment of pro-BNP

An increased level of which of the following analytes serves as laboratory evidence of cardiac ischemia?
lactate
cTnT
CK-MB
BNP

lactate

Cardiac muscles use a series of enzymes to maintain a high energy reserve. The enzyme _____ functions to regenerate ATP by combining a phosphate group from an energy-reserve molecule with ADP. The enzyme _____ also ensures adequate ATP levels by combining two ADP molecules into ATP and AMP. The enzyme _____ functions to prevent
MK, AD, CK
AD, MK, CK
CK, MK, AD
AD, CK, MK

CK, MK, AD

The resting heart’s fuel of choice is _______ but upon the imposition of a heavy workload, the heart will greatly increase its rate of ______ consumption.
lactate, free fatty acids
free fatty acids, glucose
glucose, free fatty acids
glucose, lactate

free fatty acids, glucose

An ideal cardiac marker should be elevated in the circulation for how long following a cardiac event?
1 to 2 months
1 to 3 years
At least several days
1 to 3 hours

At least several days

Which of the following laboratory tests would be the most useful in assisting the physician in differentiating congestive heart failure from other conditions that have similar clinical presentations?
cTnI
BNP
lactate
CK-MB

BNP

Of the drugs used to treat cardiac muscle disease, which of the following requires the closest laboratory monitoring of drug concentration in the body?
quinidine
digoxin
procainamide
lidocaine

digoxin

The first myocardial marker to elevate following the onset of MI symptoms is ________ . The concern with this marker is ______
myoglobin, this marker is considered nonspecific
CK-MB, this may return to normal before a blood sample can be collected
cTnT, this marker is considered nonspecific
cTnI, this may return to normal before a blood sample can be collected

myoglobin, this marker is considered nonspecific

Usually ______ are required after the onset of chest pain before CK-MB or the troponins become elevated in the serum of patients suffering from a myocardial infarction
1 to 2 hours
6 to 8 hours
4 to 6 hours
2 to 4 hours

4 to 6 hours

Troponin remains elevated in blood for how long after a myocardial infarction?
3 to 7 days
4 to 10 days
3 to 7 hours
4 to 10 hours

4 to 10 days