Studied by 30 people
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
