CHEM01 - Instrumentation and Methods

The measure of oxygen in blood by means of the Clark O2 electrode involves which of the following?

A)  Measurement of current as O2 is reduced by a platinum electrode.
B)  Measurement of current resulting from an increase of free silver ions formed by O2 oxidation of silver metal
C)  Oxidation of H2O to H2O2 followed by a peroxidasecoupledmeasurement of the H2O2.
D)  Ionselectiveelectrode sensitive to free silver ions generated by O2 oxidation of silver metal

Measurement of CO2 in blood by means of the Severinghaus pCO2 electrode is best described by which ofthe following?

A)  Measurement of pH and calculation of pCO2 from the linear relationship between pCO2 and pH insolution
B)  Biosensor that measures H2CO3 formed when carbonic anhydrase combines CO2 and H2O.
C)  Measurement of bicarbonate by an HCO3- ion selective electrode
D)  Change in pH as CO2 reacts with a bicarbonate/carbonic acid buffer after passing through asemipermeable membrane

Gas chromatography would be best used for measurement of:

A) carbohydrates
B) cancer antigens
C) serum proteins
D) drugs of abuse

An ionselective electrode that incorporates the antibiotic valinomycin into its polymer membrane is sufficiently specific for the measurement of

A) K+
B) None of these
C) Na+
D) Ca++
E) Li+

Which of the following isolates light within a narrow region of the spectrum?

A)  Monochromator
B)  Photomultiplier
C)  Photovoltaic cell
D)  Detector

In spectrophotometry, which of the following is a mathematical expression of the relationship between absorbance and transmittance?

A)  A=log%T
B)  A=abc (or A=Ecl)
C)  Au/Cu=As/Cs
D)  A=2log%T

(T/F) Freezing point is decreased in direct proportion to the concentration of dissolved particles of a solution.
True False

(T/F) The hexokinase method for detection of glucose is a coupled enzyme reaction and measures the increase inabsorption of NADPH at 340nm.
True False

Atomic Absorption Spectrophotometry is most commonly used for analysis of

A) enzyme activators
B) porphyrins
C) heavy metals
D) vitamins

The purpose of the sample blank in spectrophotometric measurement is to 

A)  to determine the zero point of the calibration curve
B)  prevent colors inherent in the sample from contributing to measurement of an analyte
C)  to minimize crossreactivity
D)  compensate for reagent color changes

The source of monochromatic light in an atomic asorption spectrophotometer is a

A) argon laser
B)  hollow cathode lamp
C) flame
D) heated graphite tube

(T/F) The hook effect, a disadvantage in sandwich immunoassays, is due to antigen excess in a sample. This can be detected and remedied by diluting the sample and reassaying.
True False

Homogeneous immunoassays are so named because

A)  They detect a single class of compounds.
B)  They only use a single reagent
C)  Several different molecules can be detected in a single assay
D)  There is no need to separate bound from free label

A competitive inhibitor of an enzyme acts by

A)  binding to the active site of the enzyme
B)  binding to the enzyme:substrate complex
C)  combining with the substrate
D)  binding to a site on the enzyme distinct from the active site

Advantages of the "sandwich" (noncompetitive,twosite,immunometric) immunoassay include all of the following EXCEPT

A)  Can measure both small molecules (e.g., steroids) and proteins
B)  Have a greater dynamic range
C)  Can have higher specificity
D)  Can use higher antibody concentrations to drive reaction kinetics

An example of an clinical assay that might be done by affinity chromatography is

A)  measurement of glycated hemoglobin
B)  quantitation of serum IgG
C)  separation of abnormal hemoglobin species
D)  fractionation of CK isoenzymes

You calibrate a spectrophotometric assay for albumin with a saline blank and a 4.3 gm/dL calibrator. The absorbances from these the reactions are blank: 0.050 and calibrator: 0.480. Your QC sample reads 0.510. Calculate its concentration.

A)  4.6 gm/dL
B) 4.8 gm/dL
C) 5.1 gm/dL
D) None of the above
c) Cannot determine with available data

The Beer(Lambert)law can be stated as:

A)  A = 2log(%T)
B)  A = abc (or A=Ecl)
C)  %T = I/I(sub 0) x 100
D) None of the above

In gasliquidchromatography or HPLC, compounds are characterized by their

A)  Rf value
B)  signal:noise ratio
C)  relative retention time
D)  peak area or height

Clinically important (diagnostically) enzyme classes include the following EXCEPT:

A) Isomerases
B) Transferase
C) Oxidoreductases
D) Hydrolases

In an enzyme reaction, the reaction rate is linear over time when:
[E] = Enzyme concentration
[S] = Substrate concentration

A)  [E] ~ [S]
B) Always
C)  [S] greatly exceeds [E]
D)  [E] greatly exceeds [S]
E) Rarely

+Multiple forms of an enzyme derived from different genes
+Multiple forms of an enzyme derived from post translational modification

-Isobars
-Isoforms
-Isoenzymes
-Isotopes

Most clinically important enzymes are reported in what units?

A) ng
B) katal
C) IU
D) pmol

For each of the following analytes or analyte classes, choose the chromatographic technique that would be most useful in separation. No technique is used twice.

+Abnormal hemoglobins
+Drugs of Abuse
+Hemoglobin A1c
+Immunosuppressant drugs

-Size-exclusion
-HPLC
-Affinity
-Ion-exchange
-Gas-liquid

For each of the following, select the technique most commonly used in its measurement

+Blood pCO2
+Blood pO2
+Serum sodium
+Sweat chloride

-Coulometry
-Potentiometry
-Voltammetry
-Amperometry
-Atomic absorption

Vapor pressure osmometry is not recommended for use in the clinical lab because:

A)  it is affected by ambient humidity
B)  it is valid only for nonproteinaceoussamples, e.g., urine.
C)  it gives misleadingresults when used for alcohol surrogate testing
D)  it is inherently less accurate than freezing point methods

The relative retention time for a gas-liquid chromatographic peak is based upon its position relative to

A)  the internal standard
B) end of the run
C) the injection point
D)  the largest peak

(T/F) Radioimmunoassay (RIA) is seldom used currently due to health and safety issues requiring onerous handling and disposal requirements.
True False

(T/F) The LineweaverBurkplot graphs 1/[S] vs 1/Vo and allows determination of Vmax, Km.

Enzymes are measured in plasma/serum primarily as a means of assessing

A) None of these
B)  the source of increased or decreased metabolites in plasma/serum
C)  the presence of inherited enzyme deficiencies or excesses
D)  the patient's current metabolic status
E)  damage to specific tissues

For each of the following photometric techniques, match with the terms that describe:
1) how the detected light wavelength compares to the instrument monochromator output and
2) whether the photodetector is in line with the sample and light source (on axis) or at some angle to it (off axis)

+(Spectro)photometry
+Fluorimetry
+Chemiluminescence
+Nephelometry
+Turbidimetry

-shorter wavelength, on axis
-shorter wavelength, on axis
-same wavelength, off axis
-same wavelength, on axis
-longer wavelength, on axis
-longer wavelength, on axis
-no light source, no axis

The most common detection label for automated immunoassay is currently

A) fluorescence
B)  chemiluminescence
C) fluorescence polarization
D) enzyme

An advantage of competitive immunoassay is that

A) both large and small molecules can be measured
B)  it usually has a very wide dynamic range
C)  does not require separation of bound and free
D)  none of the above, noncompetitveassays are always advantageous

The presence of heterophile antibodies or HAMA in a sample would be most likely to cause a problem in which assay?

A) Glucose
B) Lactate deydrogenase
C) IgG
D) serum hCG