Med Tech Exam Review - Clinical Chemistry

centrifugal force depends on the 1. mass of the material being centrifuged 2. speed of rotation 3. radium of the centrifuge 4. temperature of the centrifuge cups

1, 2, 3 Centrifugal force depends on the mass and on the speed and radium of rotation. Since most material being centrifuged in the clinical lab have specific gravity close to 1.00, only the speed and radiu need be considered.

isolates light within a narrow region of the spectrum a. Tungsten lamp b. calomel electrode c. monochromator d. barrier layer cell e. hollow cathode lamp

C Photometric methods are based on the use of Beer's law, which is applicable only for monochromatic light. A monochromator is a device for selecting a narrow band of wavelengths from a continuous spectrum. The three kinds of monochromomators are filters, prisms, and gratings

epinephrine a. adrenal medulla b. alpha cells of the pancreas c. beta cells of the pancrease d. adrenal cortex e. anterior pituitary

A

breakdown of glycogen to form glucose and other intermediate products a. glycogenesis b. glycogenolysis c. gluconeogenesis d. glycolysis e. lipogenesis

B

glucagon a. adrenal medulla b. alpha cells of the pancreas c. beta cells of the pancrease d. adrenal cortex e. anterior pituitary

B

the column is packed with a resin. Separation dpends primarily on the sign and ionic charge density of the substances to be separated a. Paper chromatography b. Thin-layer chromatography c. Ion-exchange chromatography d. Gas-liquid chromatography e. High-performance liquid chromaography

C Ion-exchange chromatography utilizes synthetic ion exchange resins. They may be cation or antion exchange resins. They can be used either in a column or a thin layer. Separation of mixtures of substances by ion exchange chromatography depends primarily on the sign and the ionic charge density of the substances being separated

Insulin may be deescribed as 1. being synthesized from proinsulin 2. consisting of 51 amino acids 3. a two-chain polypeptide 4. being active in its C peptide form

1, 2, 3 Insulin, a two-chain polypeptide, consists of 51 amino acids. A single-chain preproinsulin is cleaved to proinsulin, which is the immediate precursor of insulin. When proinsulin is cleaved, it breaks down to form insulin, a two-chain polypeptide, and inactive C-peptide

type 1 idiopathic diabetes mellitus may be described as 1. insulin dependent 2 ketosis prone 3. Juvenile diabetes 4. Maturity-onset type

1, 2, 3 Idiopathic diabetes mellitus has been classified as insulin dependent (type 1) and non-insulin dependent (type 2). The insulin dependent type, formerly called juvenile diabetes, was renamed becasue it may occur at any age. Ketosis is . acommon occurrence with tis type. The non-insulin dependent type is not prone to ketosis and was formerly referred to as maturity onset diabetes

which of the following is characterisitc of severe hyperglycemia? 1. glycosuria 2. hyperglucagonemia 3. hyponatremia 4. ketonuria

1, 2, 3, 4 In uncontrolled diabetes mellitus, the blood glucose level exceeds the renal threshold of 160 to 180 mg/dl for glucose, leading to glycosuria and polyira. The excess secretion of glucagon stimulates lipolysis, with increased formation of acetoacetic acid. In the blood, the ketoacids dissociate, with the hydrogen ions being buffered by bicarbonate. This causes the bicarbonate to become depleted and leads to metabolic acidosis. The excretion of the ketoanions (ketonuria) is accompanied by the cations Na+, K+, and NH4+, which causes Na+ body and plasma levels to become decreased (hyponatremia).

separation depends on (1) the volatility of the sample, (2) its rate of diffusion into the stationary phase, which is a liquid layer adsorbed on the column packing, and (3) its solubility in the liquid layer a. Paper chromatography b. Thin-layer chromatography c. Ion-exchange chromatography d. Gas-liquid chromatography e. High-performance liquid chromaography

D. In GLC the stationary phase is a liquid adsorbed on particles packed in a column. The movig phase is a gas which passes through the column. Since the sample is carried in the moving phase, it must be volatile at the temperature of the solumn so that it can be carried by the gas HPLC is a form of column chromatography in which the moving phase is actively pumped through the column, thus speeding the separation process considerably

deficiency of glucose-6-phosphate resulting in hepatomegaly, lactic acidosis, and hyperlipidemia a. type I - von Gierke's disease b. type II - pompe's disease c. type III - Cori-Forbes disease d. type IV - Andersen's disease c. Type V - McArdle's disease

A type I - von Gierke's disease is clinically characterized by severe fasting hypoglycemia and lactic acidosis. This is due to a deficiency of the enzyme glucose 6 phosphatase. Glucose cannot be transported from the liver as glucose 6 phosphate during the breakdown of glycogen. It is metabolized to lactic acid and thus results in lactic acidosis

Provides radiant energy in the visible, near IR, and UV regions of the spectrum a. Tungsten lamp b. calomel electrode c. monochromator d. barrier layer cell e. hollow cathode lamp

A A tungsten lamp is the most common light source for photometry in the visible region. It provides a continuous spectrum from the near infrared (IR) through the visible to the near ultraviolet region. Most of the radiatn energy is in the near IR. Only about 15% is in the bisible region - the region usually used. Because of the large emission in the near IR, tungsten lamps generate a significant amount of heat. The effects of the heat should be considered in evaluating the design of an instrument (Is the detector protected from the heat of the lamp?) and in planning routine maintenance (Is the glass bulb opaque from consensation of vaporized tungsten on the inside or deposition of chemical fumes on the outside?)

quantity of material in an object a. mass b. weight c. sensitivity d. precision e. accuracy

A mass is the invariant measure of the quantity of mateial in an object

application of an uncharged substance such as dextran to an electrophoretic strip and observaion of the distance that it travels when a current is applied permits quantitation of this penomenon a. electrophoresis b. electroendosmosis c. rheophoresis d. mobility e. isoelectric point

B.

considered specific for beta-D-glucose; catalyzes the oxidation of glucose to cluconic acid and hydrogen peroxide; with the action of the enzyme peroxidase, forms a colored product that can be measured a. o-Toluidine b. glucose oxidase c. hexokinase d. somogyi-Nelson e. folin-Wu

B.

measures reagents and diluent and mixes them with sample a. sampler b. manifold and proportioning pump c. dialyzer d. heating bath e. colorimeter and recorder

B.

mercury covered by a layer of mercurous chloride in contact with satruated potassium chloride solution is a description of which of the following types of electrodes? a. antimony b. calomel c. hydrogen d. quinhydrone e. silver/silver chloride

B. In practical applications of potentiometry, it is desirable to use one half-cell with a known and constant potential that is not sensitive to the composition of th ematerial to be analyzed. This is called the reference electrode. One common reference electrode is the calomel electrode, which consists of mercury covered by a layer of mercurous chloride in contact with a saturated solution of potassium chloride. The other half-cell, called the indicator electrode, is selected on the basis of the change in its potential with change in the concentration of the analyte of interest

conversion of gluocse to glycogen a. glycogenesis b. glycogenolysis c. gluconeogenesis d. glycolysis e. lipogenesis

A

deficiency of alpha-1,4-glucosidase resulting in cardiomegaly, muslce weakness, death in infancy a. type I - von Gierke's disease b. type II - pompe's disease c. type III - Cori-Forbes disease d. type IV - Andersen's disease c. Type V - McArdle's disease

B type II - Pompe's disease is caused by a deficiency of alpha-1,4- glucosidase

a chloride analyzer that generates silver ins as part of its reaction mechanism operates on the principle of 1. potentiometry 2. amperometry 3. polarography 4. coulometry

2, 4

the measurement of CO2 in blood by means of a PCO2 electrode is dependent on 1. the partial pressure of CO2 in the blood 2. the change in pH due to increased carbnoic acid in the electrolyte surrounding the electrodes 3. the selective permeability of the membrane between the sample and the electrodes 4. the passage of H+ ions through the membrane between the sample and the electrodes

1, 2, 3 In a blood gas analyzer, the PCO2 electrode is actually a pH electrode immersed in a bicarbonate solution. The bicarbonate solution is separated from the sample by a membrane that is permeable to gaseous CO2 but not to ionized substances such as H+ ions. When CO2 from the sample diffuses across the membrane, it dissolves, forming carbonic acid and thus lowering the pH. The pH is inversely proporitonal to the log of the PCO2. Hence the scale of the meter can be calibrated directly in terms of PCO2. It should be noted that whereas pH refers to the negative logarithm of the H+ ion concentration, PCO2. It should be noted that whereas pH refers to the negative logarithm of the H+ ion concentration, PCO2 refers to the partial pressure of CO2

In flame emission photometry, an internal standard is used to avoid errors caused by variations in the 1. flame temperature 2. gas pressure 3. degree of atomization 4. source of sample

1, 2, 3 In flame emission photometry, an internal standard is a substance that, on excitation by heat, emits light at a wavelength sufficeintly removed from that of the analyte to be easily detectable. The internal standard - for example, lithium for analysis of sodium or potassium - is added in known concentration to the solutions to be analyzed (standards and samples). The ratio of the light generated by the lithium to the light generated by the sodium or potassium in the sample is proportional to the sample concentration. Since variations in the flame temperature, the gas pressure, or the degree of atomization of the sample will all affect the signal from the lithiumand from the sodium or potassium in the same way, errors resulting from these variations are eliminated. Flmae photometers designed for use with an internal standard must have three detectors, one each to measure the characteristic wavelength of light emitted by Na+, K+, and Li+

The chemical components of the titration solution employed in the chloride coulometric-amperometric system include 1. nitric acid 2. gelatin 3. acetic acid 4. sulfuric acid

1, 2, 3 In the coulometric titration of chloride, the titration solution into which the sample is placed contains nitric acid, acetic acid, and gelatin. The nitric acid ensures good electrical conductivity. The acetic acid reduces the slight solubility of the silver chloride produced during the titration, providing a sharper end point. The gelatin increases the reproducibility of the titration curve

which of the following statements may be associated with the activity of insulin? 1. decreases blood glucose levels 2. stimulates glucose uptake by muscle and fat cells 3. increases cell membrane permeability to glucose 4. stimulates release of hepatic gluocse into the blood

1, 2, 3 Insulin may be described as an anabolic, polypeptide hormone. By increasing cell membrane permeability to glucose, it stimulates glucose uptake by muscle, fat, and liver cells. If cellular uptake of glucose is stimulated, the glucose concentration in the circulation decreases

which of the following are discrete analyzers? 1. dupont ACA 2. ektachem 3. abbot bichromatic analyzer 4. sequential multiple analzyer computer

1, 2, 3 The Dupont ACA, The Ektachem, and the Abbott Bichromatic Analyzer are all discrete analyzers because in each instrument, each specimen is separately analzyed in its own vessel. The Sequential Multiple Analyzer Computer (SMAC) is a continuous flow instrument in which all specimens travel through the same tubing. The addition of a computer permits rapid calculation of results and enables specimens to be read without debubbling, since the computer is able to compensate for the colorimeter readings when bubbles are passing through the colorimeter

problems inherent in turbidimetry include 1. variations in particle size of samples and standards 2. rate of aggregation or settling of particles 3. need for consistent timing of sample preparation and assay 4. need to maintain a constant temperature

1, 2, 3 Turbidimetry is the measurement of the amount of light blocked by particulate matter in passing through a turbid solution. The amount of light blocked depends on the number and the size of the particles. Hence the particle size in samples and standards mus be comparable. Consistent timing of sample preparation and assay helps to avoid errors resulting from aggregation or settling of particles. The procedure is usually carried out at rom temperature. Slight variations in temperature are not critical

the advantages of the angle-head centrifuge over the horizontal-head centrifuge include 1. less air friction 2. smaller increase in sample temperature during centrifugation 3. quicker centrifugation 4. less mixing of precipitate and sueprnatant

1, 2, 3, 4

which of the following statements about anodic stripping voltammetry (ASV) are true? 1. ASV is based on polarograpy 2. ASV is suitable for analytes present in very low concentrations 3. ASV occurs in an electrochemical cell 4. ASV involves preconcentration of the analyte by electroplating

1, 2, 3, 4

Which of the following statements about a photomultiplier tube are true? 1. converts radiant energy (light) to electrical energy (current) 2. amplifies the initial signal received 3. requires a high voltage power supply 4. has a very rapid response time

1, 2, 3, 4 A photomultiplier (PM) tube has two functions: 1. it is a transducer that converts light to electricity; 2. it ampifies the signal within the tube. Amplification can be as great as 1 million times. However, an internal high voltage, as much as 1500 V must be applied. The emissionof electrons by a light-sensitive surface, i.e., the conversion of light energy to electrical energy,is virtually instantaneous. Hence, PM tubes have a very rapid response time

At present, plasma or serum is used, rathe rthan whole blood, for glucose determination because 1. glucose is more stable in separated plasma or serum 2. glucose values in whole blood may vary with the hematocrit 3. specificity for glucose is higher with most mehtods when plasma or serum is used 4. it is convenient to use with automated instruments because whole blood requires mixing immediately before sampling

1, 2, 3, 4 Glucose determinations are generally performed on serum or plasma rather than whole blood. The volume of glucose tests performed in the lab has increased considerably, making automated instruments more convenient and practical to use presently. Serum or plasma is more convenient to use than whole blood in most automated systems because serum does not require mixing before sampling. Glucose stability is greater in separated plasma than whole blood because glycolysis does not occur. Specificity for glucose is higher when plasma or serum is used because variations attributable to interferring substances in the red clels are avoided. Glucose values in whole blood usually vary as the hematocrit varies

which of the following may be associated with fluorescence polarization? 1. polarized light used for sample excitation 2. large molecular complexes show a greater amount of polarization 3. emitted fluorescence measured in both the vertical and horizontal planes 4. homogenous technique employed in fluorophore-ligand immunoassays

1, 2, 3, 4 Instrumentation employing fluorescence polarization is used for measuring therapeutic drug levels. In these immunological assays, plane-polarized light excites fluorophors in the sample cuvet. The free fluorophore-labeled ligands rotate freely becasue of their small size and primarily emit depolarized light. The labeled ligand-antibody complexes rotate slower because of their large size and emit polarized fluorescent light. Because of the differences in emitted light, it is not necessary to separate free from bound fluorophore-labeled ligands, allowing for use of the homogenous assay technique. The emitted fluorescence intensity is measured by a polarization analyzer in the vertical plane, followed by its 90 degree movement for measurement in the horizontal plane. The amount of polarized light detected is inversely proportional to the concentration of ligand in the serum sample

standardization of a flame photometery should be rechecked in which of the following circumstances? 1. when a new batch of lithium diluent is used 2. after every five to ten samples 3. when the lithium balance is adjusted 4. when the potassium range is changed

1, 2, 3, 4 When any part of a procedure is changed, the standardization of the instrument involved must be rechecked. When a large group of samples is to be assayed, known stnadards must be frequently interspersed, usually after every five to tens amples in flame photometry. Since lithium is used as the internal standard, any variation in its concentration caused by a new batch of lithium diluent or by variation in the lithium balance indicator warrants the rechecking of both the sodium and potassium standards. When urine samples are assayed, it is common to electronically expand the potassium range enfold. This range change should be accompanied by restandardization of the instrument by means of a potassium standard of a representative concentration (e.g., 100 mmol/L)

which of the following may be associated with bioluminescence? 1. light emission produced with return of electron to ground state 2. less sensitive than direct fluorescent assays 3. as sensitive as radioimmunoassay 4. electron excitation caused by radiatn energy

1, 3 Bioluminescence is a type of chemiluminescence in which the excitation energy is supplied by a chemical reaction rather than by radiant energy, as in fluorescence and phosphorescence. Bioluminescence assays have been developed for alcohol, testosterone, creatine kinase, and lactate dehydrogenase employing either NAD(P)H oxidoreductase-bacterial luciferase or an adenosine triphosphate-firefly luciferase system. Bioluminescence assays are nonradioactive, having snesitivity levels in the picomole range, which makes them as sensitive as radioimmunoassays and more sensitive than direct fluorescence assays

Which of the following may be associated with reflectance spectrophotometry as it relates to the dry reagent slide technique? 1. light projected to the slide at 45-degree angle 2. dye concentration directly proportional to reflectance 3. photodetector positioned at 90 degree angle to reflected light 4. reflectance values linearly proporitonal to transmission values

1, 3 In the dry reagent slide technique, as light from a radiant energy source passes through an interference filter, it is projected to the slide at a 45 degree angle. The light then follows a path through the clear support material and reagent layer and hits a white spreading layer; the unabsorbed light is then reflected back through the reagent and support layers. This reflected light impinges on the photodetector, which is positioned at a 90 degree angle to the slide. Since reflectance values are neither linearly proportional to transmission values nor consequently to dye concentration, the microcomputer utilizes an algorithm as a linearizing transformation of reflectance values to transmission values so that concentration may be transmission values so that concentration may be calculated

which of the following statements about atomic absorption spectrophotometry are true? 1. it requires that the element to be measured be brought to a nonionized ground state 2. it is less sensitive than flame photometry 3. it uses a hollow cathode lamp as the light source 4. it uses a cathod emade of the elemtn lithium

1, 3 Atomic absorption spectrophotometry (AAS) is based on the principle that atoms in a basic ground state are capable of absorbing energy in the form of ight at a specific wavelength. Since most samples usually have the analyte in the form of a compound or an ion, the analyte must first be converted to nonionized atoms. This is achieved by heating in a flame. About 99% of the atoms of analyte in the flame are in the ground state and therefore, are capable of absorbing energy at the appropriate wavelength. Hence, light absorbed is essentially proportional to the concentration of the analyte. AAS is therefore about 100 times more sensitive than flame photometry, which depends on the emission of light from excited atoms that compose only about 1% of the total number of atoms of the analyte. The light source in AAS is a hollow cathode lamp in which the cathode contains the element that is to be measured

fluorometers are designed so that the path of the exciting light is at a right angle to the path of the emitted light. The purpose of this design is to 1. prevent light from the excitation lamp from reaching the detector that is positioned to receive the emitted fluorescent light 2. prevent loss of emitted light 3. permited placing baffles around the cuvet so that light from the source lamp will not be reflected from the surface of the cuvet to the detector 4. prevent loss of the excitation light

1, 3 In a fluorometer, light from the excitation lamp travels in a straight line, whereas the fluorescent light is radiated in all directions. If the detector for the emitted fluorescent light is placed at a right angle to the path of the excitation light, the excitation light will not fall on the detector. In addition, baffles can be palced around the cuvet to avoid reflection of the exciting light from the surface of the cuvet to the detector. The right-angle configuration does not prevent loss of the exciting or the emitted light

Interference in the quantitation of chloride by means of a coulometric-amperometric system may be caused by the presence in the test solution of 1. bromide ions 2. calcium ions 3. sulfhydryl ions 4. hydrogen ions

1, 3 In the quantitation of chloride by a coulometric-amperometric system, other substances that combine with the Ag+ ions generated by the coulometric circuit will cause falsely elevated results. Such substances include halogens other than chloride, for example, bromide. In addition, sulfhydryl groups and thiocyanate and cyanate ions also interfere

Gravitational force exerted on an object a. mass b. weight c. sensitivity d. precision e. accuracy

B weight is the gravitation force with which an object is attracted to the earth weight = mass x gravity

scintillation counters are used in the clinical laboratory to detect which of the following emissions? 1. beta 2. alpha 3. gamma 4. flame

1, 3 Radionuclides are quantitated by measuring the amount of energy that they emit. This can be in the form of alpha emission (4/2 He+2), beta emission (electrons ejected from the nucleus of a radioisotope during radioactive decay), or gamma emission (electromagnetic radiation emitted during radioactive decay). Beta and gamma emissions can be detected by scintillation counters. The sensing element of a scintillation counter is a fluor, a substance capable of converting radiation energy to light energy. The light energy is converted to electrical energy and amplified by a photomultiplier tube. A fluor commonly employed in solid scintillation counters is a large crystal of sodium iodide containing a small amount of thallium as an activator; it is used for gamma counting. Beta emission is counted by liquid scintillation counters using fluors dissolved in organic solvents. Alpha emission has very low penetrating power and is not measured in the clinical laboratory. Flame emission gives a continuous beam of light that scintillation counter is not desinged to measure

the function of the flame in atomic absorption spectroscopy is to: 1. serve as a sample cuvet for the specimen 2. absorb the energy emitted from the metal analyte in returning to the ground state 3. bring the metal analyte to its ground state 4. supply the thermal energy needed t excite the metal analyte

1, 3 The basis of AAS is the measurement of light, at a specific wavelength, that is absorbed by an element whose atoms are in a ground state. The flame in AAS serves two functions - to accept the sample, thus serving as a cuvet, and to supply heat for converting the element, which is usually present in the sample in molecular form, into its atomic form at ground state energy level

To calibrate the pH electrode in a pH/blood gas analyzer, it is necessary that 1. the temperature of the system be regulated to 37 C 2. the barometric pressure be known and used for adjustments 3. two buffer solutions of known pH be used 4. calibrating gases of known high and low concentrations be used

1, 3 a pH/blood gas analyzer contains a pH sensitive glass electrode, a PCO2 electrode, and a PO2 electrode. The glass electrode is calibrated by comparison with two buffers of known pH. Since pH readings are temperature sensitive, the calibration must be carried out at a constant temperature. pH readings are not appreciably sensitive to changes in barometric pressure. Note that if the PCO2 and PO2 electrodes were also to be calibrated, then it would be essential to know the barometric pressure, since that affects the PCO2 and PO2 callibrating gases

which of the following components would be associated with a high-performance liquid chromatography system? 1. sample introduction system 2. column 3. solvent-delivery system 4. detector

1,2,3,4 High-performance liquid chromatography systems are composed of four basic units: sample-introduction system, solvent-delivery system, column, and detector. The sample-introduction system is generally a fixed-loop injection valve, which allows the sample to be injected into a stainless steel external loop for flushing onto the column by the solvent. The solvent-delivery system may be composed of one or two pumps for the purpose of forcing the mobile phase and sample through the column. Photometric, fluorometric, and electrochemical detectors are available for monitoring the eluate as it emerges from the column

which of the following may be used to verify spectrophotometer wavelength accuracy? 1. didymium glass filter 2. nickel sulfate solution 3. holmium oxide glass filter 4. deuterium lamp

1,2,3,4 Wavelength calibration of a spectrophotometer is performed to verify that the radiant energy emitted from the monochromator through the exit slit is the same as the wavelength selector indicates. The glass filters holmium oxide, used in the UV and visible ranges, and didymium, used in the visible and near infrared (IR) regions, are employed to check wavelength accuracy. Solutions of stable chromogens such as nickel sulfate may be used. Source lamps may be replaced with mercury vapor or deuterium lamps. These lamps have strong emission lines and provide the most accurate method of wavelength calibration

Most atomic absorption spectrophotometers incorporate a beam chopper and a tuned amplifier. The purpose of these components is to avoid errors caused by 1. variations in flame temperature 2. measurement of light form the flame 3. deterioration of the hollow cathode lamp 4. measurement of light of the specific wavelength emitted by the analyte

2, 4 a beam chopper is a device for interrupting a beam of light so that a pulsed beam is produced. In an atomic absorption spectrophotometer, if the light enetering the flame from the hollow cathode lamp is pulsed, then the light leaving the flame will consist of unabsorbed pulsed light and unpulsed light from the flame and from a small amount of emission by excited atoms of the analyte. The detector has an amplifier that is tuned to recognize and amplify only the pulsed signal. Thus errors caused by light from the flame and light emitted by the analyte are avoided. However, the beam chopper and tuned amplifier do not compensate for errors introduced by variations in flame temperature or deterioration of the hollow cathode lamp

in the field of automated analytic instruments, notable differences between discrete analyzers and continuous flow analyzers include 1. carryover between one specimen and another cannot occur in continuous flow analyzers 2. discrete analyzers use semiautomatic or automated pipetting devices 3. continuous flow systems use semiautomated pipets 4. no cross-contamination occurs between specimen-reagent mixtures in a discrete analyzer

2, 4 Discrete analyzers are designed so that each specimen is analyzed separately in its own vessel. In continous flow analyzers, all specimens flow through the same tubing. Hence carryover or cross contamination can occur in continous flow anlayzers if suitable precautions are not taken. It cannot occur between specimens in a discrete analyzer because each specimen-reagent mixture is analyzed in a separate vessel. No pipets are used in continuous flow analysis. Samples and reagents are measured by means of a peristaltic pump drawing liquids through tubing of known inner diameter and length. Depending on the specific instrument, discrete analyzers use either semiautomatic or automated pipetting devices

which type of elution technique may be used in high-perfromance liquid chromatorgraphy? 1. amphoteric 2. isocratic 3. isoelectric 4. gradient

2, 4 In HPLC, the technique used for the mobile phase may be isocratic or gradient elution. With isocratic elution the strength of the solvent remains constant during the separation. With gradient elution the strength of the solvent is continually increased (percent per minute) during the separation process. The gradient elution technique is sometimes employed to improve HPLC resolution and sensitivity

the measurement of oxygen in blood by means of a PO2 electrode involves the use of which of the following? 1. A Wheatstone bridge arrangement of resisteive elements sensitive to oxygen concentration 2. a polypropylene membrane selectively permeable to oxygen 3. a change in current resulting from an increase of free silver ions in solution 4. a direct relationship existing between the amount of oxygen in the sample and the amount of current flowing in the measuring system

2, 4 In a blood gas analyzer, the electrode for measuring the partial pressure of oxygen (PO2) in the blood is an electrochemical cell consisting of a platinum cathode and a Ag/AgCl anode connected to an external voltage source, usually a 1.35 V mercry cell, that provides a polarizing voltage of about 650 mV. The cathode and anode are immersed in buffer containing KCl. A membrane selectively permeable to gases separates the buffer from the blood sample. When there is no oxygen diffusing into the buffer, there is practically no current flowing between the cathode and the anode because they are polarized. When oxygen diffuses into the buffer from a sample, it is reduced at the cathode. The electrons necessary for this reduction are produced at the anode. Hence a current flows; the current is directly proporitional to the PO2 in the sample

A flame photometer must have which of the following components? 1. Tungsten lamp 2. Atomizer 3. Cuvet holder 4. Flame

2, 4 In a flame photometer, the atomizer disperses the sample into very small droplets that are made accessible to the flame. The flame provides the heat necessary to excite the orbital electrons that subsquently give off the absorbed energy in the form of light of characterisitc wavelengths as they return to ground state. No cuvet is used becasue the sampls are sprayed directly into the flame

which of the following may be associated with the colloid osmotic pressure (COP) osmometer? 1. measurements expressed as milliosmoles per kilogram of H2O 2. known as a membrane osmometer 3. measures total serum osmolality 4. negative pressure on reference (saline solution) side equivalent to COP of sample

2,4 The colloid osmotic pressure (COP) osmometer is ocmposed of a semipermeable membrane that separates two chambers, a mercury manometer, a pressure transducer, and a meter. When a serum sapmle is introduced into the sample chamber, saline solution from the reference chamber moves across the membrane by osmosis. This causes the development of a negative pressure on the saline side that is equivalent to the COP, which represents the amount of protein in the serum sample. COP osmometers measure the serum protein contribution to the total osmolality in terms of millimeters of mercury. COP levels are helpful in monitoring intravenous fluid therapy

aspirates water and air between each specimen a. sampler b. manifold and proportioning pump c. dialyzer d. heating bath e. colorimeter and recorder

A

chemical reaction involves the condensation of gluocse with this aromatic amine in hot glacial acetic acid solution to produce a colored product a. o-Toluidine b. glucose oxidase c. hexokinase d. somogyi-Nelson e. folin-Wu

A

In the analytic technique of potentiometry, a comparison is made between the voltage of one half-cell connected to another half-cell. It is customary that all half-cell potentials be compared to the potential generated by a standard electrode. This standard electrode is: a. A hydrogen electrode b. a calcium electrode c. a potassium electrode d. a copper electrode e. an iron electrode

A. a half-cell, also called an electrode, is composed of a single metallic conductor surrounded by a solution of electrolyte. An electrochemical cell consists of two half-cells. If two different kinds of half-cells are connected in such a way as to make a complete circuit, a current will flow because of the potential difference between the two electrodes. The connection must be between the two electrolyte solutions, usually by means of a salt bridge. The universally accepted standard half-cell with which all other half-cells are compared is the hydrogen electrode, arbitrarily assigned a potential E of 0.000 volt

which of the following carbohydrates is a polysaccharide? a. starch b. sucrose c. lactose d. glucose e. dextrose

A. there are three major classifications of carbohydrates: monosaccharides, disaccharides, and polysaccharides. Starch is classified as a polysaccharide because its structure is composed of many molecules of glucose (a monosaccharide) condensed together. Monosacharides are carbohydrates with the general molecular formula Cn(H2O)n that can not be broken down to simpler substances by acid hydrolysis. Disaccharides are condensation products of two molecules of monosaccharide with loss of one molecule of water

glucose concentration in whole blood is a. less than the concentration in plasma or serum b. greater than the concentration in plasma or serum c. equal to the concentration in plasma or serum d. unmeasureable because of a high concentraiton of red blood cells e. meaningless because it is not stable

A. when highly specific analytic methods are used, the normal gluocse concentration in human whole blood is 65 to 95 mg/dl. In human plasma or serum, the normal gluocse concentration is higher, 70 to 105 mg/dl. the difference occurs because glucose diffuses freely between plasma and red cells, and there is a higher concentration of water in plasma than in red cells. the water content of whole blood depends on the hematocrit

the stationary phase is silica gel spread on a piece of glass or plastic. The moving phase is a liquid that penetrates the solid phase by capillary action a. Paper chromatography b. Thin-layer chromatography c. Ion-exchange chromatography d. Gas-liquid chromatography e. High-performance liquid chromaography

B TLC is similar to paper chromatography, but the stationary phase is a thin layer of some sorbent such as silica gel uniformly spread on a piece of glass or plastic

if a paper strip saturated with water is placed in an electrophoresis chamber with water in each of the buffer reservoirs and a current is passed through the aper, water flows from the anode reservoir to the cathode reservoir a. electrophoresis b. electroendosmosis c. rheophoresis d. mobility e. isoelectric point

B if a paper strip saturated with water is placed in an electrohporetic chamber contaiing only water in the buffer reservoir sand a current is applied, some water will flow from the anode to the cathode. this phenomenon is called electroendosmosis. It occures because the paper is intself negatively charged as a result of the adsorption of some hydroxyl ions on the surface of the paper. These fixed negative charges attract a layer of residual positively charged ions that are free to move within the water. These positively charged ions are themselves highly hydrated. Hence when a current is applied, the positively charged ions move twoard the cathode, carrying water molecues with them. electroendosmosis can be observed and quantitated by applying an uncharged substance such as dextran to an electrophoretic strip, applying a current, and observing the migration of the uncharged dextran, which is swept along with the moving water

given the following information on a particular compound that has been visualized by means of thin-layer chromatography, calculate the Rf of the compound - distance from origin to spot center = 48 mm - distance from spot center to solvent front = 93 mm - distance from origin to solvent front = 141 mm a. 3 b. 34 c. 52 d. 66 e. 294

B. In thin-layer chromatography (TLC) the Rf describes the distance traveled by the solute (compound of interest) in relation to the distance traveled by the solvent (mobile phase). Measurements of the TLC plate are made from the origin or point of sample application to the center of the developed spot and from the origin to the solvent front. An Rf may be calculated by means of the following formula: Rf = (distance from origin to spot center/ distance from origin to solvent front) x 100 The Rf o fthe compoound of interest, along with chromogenic spray characteristics, may then be compared with standards for identification of the unknown compound

in flame emission photometry, a photon of light with a wavelength specific for a given element is emitted when a. an orbital electron is raised to a higher energy state b. an excited orbital eelctron returns to the ground state c. the element absorbs ultraviolet light d. the bonds in the molecule vibrate e. light of a wavelength that is any multiple of the wavelength specific for the given element falls on the given element

B. Many metallic elements can absorb enegy in the form of heat. This moves their orbital electrons from the ground state to a higher energy level that is unstable. As the excited electrons drop back to the ground state, they give off their energy in the form of light at specific wavelengths unique for each element. The amount of light given off can be correlated to the amount of element present. This phenomenon provides the basis for flame emission photometry. Flame photometry is most commonly used for determination of Na+, K+, and Li+

nephelmoetry is a method of assay based on the measurement of the light that is a. absorbed by particles in suspension b. scattered by particles in suspension c. produced by fluorescence d. produced by excitation of ground state atoms e. not blocked by passage through an opaque suspension

B. Nephelometry is the measurement of the amount of light scattered by particles in suspension. The amount of light scattered depends on the size and shape of the particles and on the wavelength of the incident light. Ultraviolet light should not be used because it might produce some fluorescence, which would lead to erroneously high results

an oral glucose tolerance test is administered to a patient. the following values are obtained fasting - 80 mg/dl; 30 mintues - 90 mg/dl; 1 hour - 87 mg/dl; 2 hours - 85 mg/dl/ and 3 hours - 80 mg/dl the tolerance test is repeated on the same patient by the intravenous method and the following values are obtained: fasting - 80 mg/dl; 30 minutes - 145; 1 hour - 130; 2 hours - 75; and 3 hours - 80 the most likely explanation for the differences is a. values obtianed were done by two different methods b. poor absorption of the orally administered glucose c. specimens were interchanged on the oral glucose toelrance test d. results on the intravenous glucose tolerance test are not reasonable or reliable e. results on the oral glucose tolerance test are not reasonable or reliable

B. The glucose tolerance test is performed to assess the body's response to glucose. In the "norma" glucose tolerance curve, the highest level of blood gluocse is usually found at 1 hour. The level then falls to slightly below the fasting value at 2 hours and returns to the fasting value in about 3 hours. In a "diabetic" glucose tolerance curve, the most significant finding in the diagnosis of diabetes is the failure of elevated gluocse levels to fall within 2 hous. The peak level is above normal, and fasting levels may or may not be elevated. In a "flat" glucose tolerance curve, the blood glucose level fails to rise normally following a glucose load. This type of curve is sometimes considered to indicate malabsorption

given the following information, calculate the plasma osmolality in milliosmoles per kilogram: sodium - 142; glucose - 130; urea nitrogen - 18 a. 278 b. 287 c. 290 d. 298 e. 299

B. When the osmolality has been both measured in the laboratory and calculated, the osmolal gap may then be determined by substracting the calculated osmoality from the measured. Plasma osmolality may be calculated whne the plasma sodium, glucose, and urea nitrogen values are known. Use the following equation. Note that glucose, Na, and urea are all mmol/L calculated osmolality = 1.86 (Na+) + glucose + urea nitrogen +9

glucose is stored in muscle and the liver as a. triglyceride b. glycogen c. maltose d. lactose e. starch

B. glycogen is a polysaccharide composed of many glucose molecules. In contrast to the amylopectin molecule, a glycogen molecule is more highly branched and more compact.Glycogen is found in a variety of animal tissues, particuarly in the liver, providng the storage form for carbohydrates in the body. When energy requirements warrant it, glycogen may be broken down to glucose by a series of phosphorylating and related enzymes

the following glucose tolerance test results are indicative of what state? glucose values as assayed by glucose oxidase method are fasting - 130 mg/dl; 30 min - 165 mg/dl; 60 minues - 225 mg/dl; 90 minutes - 170 mg/dl; and 120 minutes - 150 mg/dl a. normal b. diabetes c. addisons disease d. hyperinsulinism e. hypothyroidism

B. most clinicians use the gluocse tolerance test to confirm or define diabetes chemically. the glucose tolerance test is used to observe the response of the patient to a gluocse load or challenge. This can be done by either an oral or an intravenous load of gluocse. There are many crieria for the diangosis of diabetes mellitus. These have been evaluated by committe on statisitcs of the american diabetes association. Widely used criteria are those provided by the Wilkerson point system or the Fajans-Conn criteria

in an electrolytic cell, the half-cell where reduction takes place is known as the a. anode b. cathode c. inidcating electrode d. reference electrode e. standard electrode

B. oxidation involves the loss of electrons, and reduction the gain of electrons. In an electolytic cell composed of two different half-cells - for example, zinc in zinc sulfate and copper in copper sulfate - electrons will flow from the anode to the cathode. thus reduction takes place at the cathode

generates an electric current when light falss on it a. Tungsten lamp b. calomel electrode c. monochromator d. barrier layer cell e. hollow cathode lamp

D Barrier layer cells are transducers that convert light energy into electrical energy. They are based on the fact that when light falls on certain metals and smeiconductros, e.g., selenium, electrons will flow to a suitable receptor in proportion to the intensity of the light. A layer of iron provides the receptor; a layer of selenium covered with transparent electrical conductive material provides the surface that receives the light. When these two layers are connected through a galvanometer, the electrical energy generated by the light can be directly measured, usually without any amplification

the test commonly used as a reliable index of intestinal carbohydrate absorption is a. glucose fasting b. D-xylose c. insulin d. glucose tolerance test .e maltose

B. the D-xylode absorption test is significant in distinguishing two types of malabsorption: intestinal malabsorption and malabsorption resulting from pancreatic insufficiency. When D-xylose is administered orally, it is absorbed by passive diffusion into the portal vein from the proximal portion of the small intestine. Since D-xylose is not metabolized by the liver, it is excreted unchanged by the kidneys. Inintestinal malabsorption, the amount of D-xylose excreted, as measured in a 5 hour urine specimen, is less than normal because of decreased absorption of D-xylose. In malabsoption caused by pancreatic insufficiency, the absorption of D-xylose is normal

catalyzes the phosphorylation of gluocse by adenosine triphospahte, forming glucose-6-phosphate and adenosine diphosphate; the absorbance of NADPH produced is read at 340 nm a. o-Toluidine b. glucose oxidase c. hexokinase d. somogyi-Nelson e. folin-Wu

C

formation of gluocse from noncarbohydrate sources a. glycogenesis b. glycogenolysis c. gluconeogenesis d. glycolysis e. lipogenesis

C

insulin a. adrenal medulla b. alpha cells of the pancreas c. beta cells of the pancrease d. adrenal cortex e. anterior pituitary

C

removes large molecular weight substances and some of the analyte a. sampler b. manifold and proportioning pump c. dialyzer d. heating bath e. colorimeter and recorder

C

deficiency of the debrancer enzyme, resulting in hepatomegaly and muscle weakness a. type I - von Gierke's disease b. type II - pompe's disease c. type III - Cori-Forbes disease d. type IV - Andersen's disease c. Type V - McArdle's disease

C Type III - Cori-Forbes disease is caused by the absence of a debrancer enzyme. This disease is characterized by hypoglycemia, hepatomegaly, seizures, and growth retardation

when buffer evaporates from a paper strip during electrophoeresis, buffer flows from both reservoirs toward the center of the paper strip a. electrophoresis b. electroendosmosis c. rheophoresis d. mobility e. isoelectric point

C electrophoresis is a method of separating charged particles by their rates of migration in an electric field. An electrophoretic chamber consists of two reservoirs to hold buffer, a means of supporting a strip in the chamber so that one end is dpping into each of the reservoirs, and a means of applying an electric current to the strip. The whole chamber is sealed to make it vaporproof. If buffer evaporates from a paper strip during electrophoresis, buffer will flow from both reservoirs toward the center of the pape strip. this phenomenon is called rheophoresis

consists of a layer of dielectric material between two thin-silvered pieces of glass a. Tungsten lamp b. calomel electrode c. monochromator d. barrier layer cell e. hollow cathode lamp

C An interference filter consists of who thin-silvered pieces of glass that are semitransparent. A layer of transparent dielectric material is sandwiched between the pieces of glass. The thickness of the layer of dielectric determines the wavelength of light that will be transmitted

in an analytic balance, the number of scale divisions deflected by a weight of 1 mg a. mass b. weight c. sensitivity d. precision e. accuracy

C sensitivity of an analytic balance is the number of sclae divisions deflected by a weight of 1 mg

the main advantages of fluorometric over spectroscopic methods of analysis are a. decreased specificity and decreased sensitivity b. decreased specificity and increased sensitivity c. increased specificity and increased sensitivity d. increased specificity and decreased sensitivity e. ease of obtaining suitable quality of reagents

C. Fluorescence occurs when a molecule absorbs light of a particular wavelength and is thereby stimulated to emit light of a longer wavelength. The emitted light has a characteristic spectrum, the emission spectrum, that is unique for each fluorescing molecule. Hence, fluorometric methods are extremely sensitive and highly specific. Becasue of this extreme sensitivity, reagents used must be of a higher degree of purity than is required for spectroscopy since even slight traces of impurities may fluoresce

to achieve the best levels of sensitivity and specificity, a type of detector system that a gas chromatograph may be coupled to is a (an) a. UV spectrophotometer b. bicrhomatic spectrophotometer c. mass spectrometer d. fluorescence detector e. electrochemical detector

C. The column and carrier gas flow rate used in gas chromatography are important aspects of the separation and resolving power of the system. When the column eluent is introduced into a mass spectrometer, additional information pertaining to elemental composition, position of functional groups, and molecular weight may be determined for the purpose of identifying compounds, e.g., drugs, in biologic samples. Mass spectrometers consist of a vacuum system, ion source, mass filter, and detector

deficiencyof brancer enzyme, resulting in cirrhosis and hepatic failure a. type I - von Gierke's disease b. type II - pompe's disease c. type III - Cori-Forbes disease d. type IV - Andersen's disease c. Type V - McArdle's disease

D type IV - Andersen's disease is caused by a deficiency of brancher enzyme. It is a rare disease characterized by progressive liver enlargement or cirrhosis and muscular weakenss by the age of 2 months. Storage glycogen is not usually found, but unbranched amylopectin accumulates i this disease

Colligative properties of solutions include all of the following except: a. boiling point b. freezing point c. pH d. osmotic pressure e. vapor pressure

C. colligative properties of a solution are those properties that depend only on the number of particles in solution, not on the nature of the particles. The colligative properties are boiling point, freezing point, osmotic pressure, and vapor pressure. Terms used to describe the concentration of particles in solution are osmole (the number of particles, 6.0224x10^23, that lowers the freezing point 1.86C) and osmolal (the concentration of 1 osm of solute per kilogram of water). One mole of an unionized solute dissolved in 1 kg of water lowers the freezing pont 1.86C. thus it is an osmolal solution. For un-ionized substances such as glucose, 1 mol equals 1 osm. For substances that ionize, such as sodium chloride, werein each molecule in solution becomes two ions and thus two particles, 1 mol of sodium chloride theoretically equals 2 osm. In practice, howerever, this is not always the case; an osmotic activit coefficient factor is used to correct for the deviation

when the pH-sensitive glass electrode is not actively in use, it should be kept in a. distilled or deionized water b. physiologic saline solution c. the medium recommended by the manufacturer d. a buffer solution with a pH near the pH of the internal solution in the electrode e. a buffer solution with a pH near the pH at which the electrode is to be used

C. for optimum performance, pH-sensitive glass electrodes that are not actively in use should be kep timmersed in an aqueous medium. Since the exact composition of the pH-sensitive glass varies from one manufacturer to another, the glass electrode should be maintained in the medium recommended by the manufacturer. Usual media are water, dilute HCl, and buffer with a pH near the pH of the solution to be measured. The functioning of a glass electrode depends on the properties of the pH-sensitive glass. A typical glass electrode is made by sealing a thin piece of pH-sensitive glass at the end of a piece of glass tubing and filling the tube with a solution of hydrochloric acid saturated with silver chloride. A silver wire is immersed in the solution in the tube with one end extending outside the tube for external connection. This is essentially a silver/silver chloride reference electrode sealed within the tube with the pH-sensitive glass tip. This pH-sensitive glass functions appropriately only when it is saturated with water. Then eac surface of the glass develops a hydrated latice, where exchange of alkaline metal ions in the lattice for hydrogen ions in the test solution can occur

the ferricyanide method requires a reuding sugar. the disaccharide that would not be suitable for use i this test is a. maltose b. lactose c. sucrose d. amylose e. amylopectin

C. the alkaline ferricyanide test for glucose is based on the reducing properites of glucose. Hence, other reducing substances will interfere with the test. The reducing properties of monsaccharides are attributable to the presence of a free aldehyde or ketone group. When two monosaccharides combine through their aldehyde or ketone groups to form a disaccharide that has no free aldehyde of ketone group, the disaccharide formed is not a reducing surgar. sucrose is a nonreducing disacchardie. It consists of glucose and fructose, combined through their aldehyde and ketone groups. Similarly, amylose and amylopectine both consist of long chains of gluocse molecules with a linkage between the aldehyde group of on molecule and a hydroxyl group of the next molecule. Consequently, amylose and amylopectin do not react in the ferricyanide methode; however, they are not disaccairdes

centrifugal analyzers utilize centrifugal force for the purpose of a. aspirating sample b. aspirating reagents c. mixing sample and reagents d. separating proteins and high molecular weight substances e. intensifying color development in colorimetric procedures

C. the heart of a centrifugal analyzer is the disk that contains an inner ring of compartments into which the reagent is placed (either manually or by automated pipets) and an adjacent ring of compartments into which the sample is placed. In systems that utilize plastic disposable disks, this second ring of compartments also serves as cuvets. A third ring of compartments is available in some instruments into which a second reagent is placed. Systems that utilize nondisposable Teflon disks are quipped with a fourth ring in which the compartments serve as part of the outer periphery of the spinning rotor assembly. In this case the ring of cuvets is separate from the disk but concentric with it. When the loaded disk is spun at high speed, centrifugal action drives the reagent into the sample and then drives this mixture directly into the cuvet. A single light source and detector are aligned in such a way that the spinning cuvets all pass through the beam of light. Microprocessors are used to program the instruments and make all necessary calculations

conversion of glucose or other hexoses into lactate or pyruvate a. glycogenesis b. glycogenolysis c. gluconeogenesis d. glycolysis e. lipogenesis

D

hydrocortison a. adrenal medulla b. alpha cells of the pancreas c. beta cells of the pancrease d. adrenal cortex e. anterior pituitary

D

proteins are precipitated in the presence of zinc sulfate and barium hydroxide; non-sugar-reducing compounds are precipitated and adsorbed on barium sulfate a. o-Toluidine b. glucose oxidase c. hexokinase d. somogyi-Nelson e. folin-Wu

D

a detector that cannot be used in instruments that have a chopper a. Tungsten lamp b. calomel electrode c. monochromator d. barrier layer cell e. hollow cathode lamp

D A barrier layer cell has too slow a response time to be used in instruments that have a chopper. A chopper is a device for interrupting a beam of light so that the detector is alternately exposed to incident light and no light. A typical frequency for chopping is 60 times/sec

in assaying an analyte with a single-beam atomic absorption spectroscope, what the instrument actually measures is the a. intensity of light emitted by the analyte on its return to the ground state b. intensity of light that the analyte absorbs from the hollow cathode lamp c. intensity of light that the analyte absorbs from the flame d. intensity of the beam from the hollow cathode lamp after it has passed through the analyte containing flame e. intensity of light emitted by the analyte when it is raised to a higher energy orbital

D. In a single-beam atomic absorption spectroscope, the amount of light that the analyte absorbs from the hollow cathode lamp is what we wish to know. However, what is actually measured is the intensity of the beam after it has passed through the flame. This measurement is made with and without sample in the flame. In this way the instrument calculates the amount of light absorbed because of the presence of the analyte in the flame

The bile salts aid in the emulsification of dietary fats in the intestines. The bile salts are composed of bile acids that have been conjugated with a. albumin b. glucuronic acid c. glucose d. amino acids e. sulfate

D. cholic acid and chenodeoxycholic acid are the two principal primary bile acids produced by the liver. The bile acids are synthesized as excretory products of cholesterol catabolism and are composed of a carbon 24 steroid nucleus. After formation in the liver, the bile acids are conjugated with the amino acids glycine and taurine for secretion into the bile and storage in the gallbladder. With fat ingestion, the bile salts are released into the intestines, where they aid in the emulsification of dietary fats. A majority of the bile acids are reabsorbed from the intestines into the enterohepatic circulation for reexcretion into the bile

the freezing point osmometer is based on the principle that a. the freezing point depression is inversely proportional to the amount of solute in the solution b. the freezing point depression varies as the logarithm of the concenration of solute c. the freezing point is raised by an amount that is inversely proportional to the concentration of dissolved particles in the solution d. the freezing point is lowered by an amount that is directly proportional to the concentration of dissolved particles in the solution e. there is no relationship between freezing point depression and the concentration of dissolved particles in the solution

D. the freezing point of an aqueous solution is lowered 1.86C for every osmole of dissolved particles per kilogram of water. These particles may be ions, for example. Na+ and Cl-, or undissociated molecules such as glucose. The freezing point osmometer is an instrument designed to measure the freezing point of solutions. It uses a thermistor that is capable of measuring very small changes in temperature

the distance that a charged particle moves during electrophoresis depends on many variables, including net charge, type of buffer, time, etc a. electrophoresis b. electroendosmosis c. rheophoresis d. mobility e. isoelectric point

D. the mobility is the distance that a charged particle moves in the electric field during electrohporesis. It depends on many variables such as net charge, type of buffer, time, and applied potential difference

Which of the following may be associated with the prostaglandins? a. 16-Carbon fatty acid b. Tetracyclin skeleton C. only found in kidney tissue D. derived from prostanoic acid E. subdivided into groups A and C

D. the term "prostaglandins" encompasses a variety of lipid compounds that are derived from the 20 carbon fatty acid, prostanoic acid. The prostaglandins are characterized by a cyclopentane ring structure. The varied attachment of functional groups on the ring allows for the differentiation of the prostalandins into the four principal naturally occurring groups, A, B, E, and F. A number of tissues, including the kidney, lung, spleen, gastrointestinal tract, thyroid, skin, and brain, possess the ability to synthesize the prostaglandins. Radioimmunoassay methods employing either an iodine-125 or a tritium label are commercially available for the quantitation of several prostaglandins

Hydrolysis of sucrose yeilds a. glucose only b. galactose and glucose c. maltose and glucose d. fructose and glucose e. lactose and glucose

D. when two monsaccharides condense with loss of a molecule of water, a disaccharide is formed. Disaccharides, therefore, can be hydrolyed into two monosaccharides. The most important disaccharides are maltose, lactose, and sucrose. On hydrolysis, sucrose will yield one molecule of glucose and one molecule of fructose. Maltose can be hydrolyzed into two molecules of glucose. Lactose can be hydrolyzed into glucose and galactose

ACTH a. adrenal medulla b. alpha cells of the pancreas c. beta cells of the pancrease d. adrenal cortex e. anterior pituitary

E

growth hormone a. adrenal medulla b. alpha cells of the pancreas c. beta cells of the pancrease d. adrenal cortex e. anterior pituitary

E

measures the reaction and presents the result in the form of a graph a. sampler b. manifold and proportioning pump c. dialyzer d. heating bath e. colorimeter and recorder

E

should be checked regularly with National Bureau of Standards Class S weights a. mass b. weight c. sensitivity d. precision e. accuracy

E

The stationary phase is a liquid adsorbed on particles packed in a column. The moving phase is pumped through the column a. Paper chromatography b. Thin-layer chromatography c. Ion-exchange chromatography d. Gas-liquid chromatography e. High-performance liquid chromaography

E Chromatography provides a variety of means of separating mixtures of substances on the basis of their physicochemical properties, primarily their solubility in a variety of solvents. Chromatographic methods always involve a stationary phase and a moving phase. The sampe containing the substances to be separated is carried in the moving phase; the moving phase passes over the stationary phas at different rates depending on their relative solubilities in the two phases. In paper chromatography, the solid phase is paper on which the sample is placed directly. The moving phase is any suitable solvent that travels along the paper by capillary action. the amount of separation depends on (1) the rate of diffusion, (2) the solubility of the substances being separated, and (3) the nature of the solvent. TLC is similar to paper chromatography, but the stationary phase is a thin layer of some sorbent such as silica gel uniformly spread on a piece of glass or plastic

a protein molecule in the form of a zwitterion carries a net charge of zero a. electrophoresis b. electroendosmosis c. rheophoresis d. mobility e. isoelectric point

E protein molecules can exist as anions, cations, or zwitterions, depending on the pH of a solution in which they are placed. The pH at which they exist in the form of zwitterions andhence have no net charge is called the isoelectric point. Electrophresis must be carried out at some pH othe rthan the isoelectric point

Which test may be performed to assess the average plasma glucose level that an individual maintaned during a previous 2- to 3- month period? a. plasma glucoe b. urine glucose c. two hour postprandial glucoe d. oral gluocse tolerance e. glycosylated hemoglobin

E.

when measuring K+ with an ion-selective electrode by means of a liquid ion-exchange membrane, what antibiotic will be incorporated into the membrane? a. monactin b. nonactin c. penicillin d. streptomycin e. valinomycin

E. The ion-exchange electrode is a type of ion-selective electrode that consists of a liquid ion-exchange membrane that is made of an inert solvent and an ion-selective neutral carrier material. A collodion membrane may be used to separate the membrane solution from the sample solution being analyzed. Because of its ability to bind K+, the antibiotic valinomycin is used as the neutral carrier for the K+-selective membrane. The antibiotics nonactin and monactin are used in combination as the neutral carrier for the NH4+-selective membrane

a sample of blood is collected for glucose in a sodium fluoride tube before the patient has had breakfas. the physician calls 2 hours later and requests that detemrinations of blood urea nitrogen (BUN) by urease method and of creatine kinase (CK) be performed on the same sample rather than obtaining another specimen. What would you tell the physician? a. you will gladly do the tests if there is enough specimen left from doing glucose b. you chould use micromethods c. you chould do the CK but not the BUN determination d. you could do the BUN but not the CK determination E. you cannot do either procedure

E. sodium floride is the anticoagulant of choice for glucose testing. It acts as a glucose preservative by inhibiting glycolysis. However, it is not suitable for use with many enzyme procedures. In the determination of CK and BUN, where urease activity is utilized, the high concentration of fluoride in the plasma acts as an enzyme inhibitor, preventing the necessary chemical reaction