Clinical Biochemistry Midterm

Front 1

If everything is the same, a molecule will migrate _________ (faster or slower) in a buffer with a higher viscosity than it will in a buffer with a lower viscocity?

Back 1

Slower

Front 2

Which of the following includes all of the key components of an electrophoretic system:

Back 2

electrical power source, the support medium, the buffer, the sample, and the detecting system

Front 3

In routine clinical electrophoresis, the most common means used to provide quantitative information about the zones that have separated involves the use of:

Back 3

densitometry

Front 4

An increase in which of the following would increase the movement of particles through a solution in electrophoresis?

Back 4

voltage applied to the electrophoretic system

Front 5

In capillary electrophoresis place the following chemical species in the order of their elution/detection time from quickest to slowest? Assume size and shape are equivalent for all species. 1-multiply charged cation 2-multiply charged anion 3-singly charged cation. 4-singly charged anion. 5-neutral molecule.

Back 5

1,3,5,4,2

Front 6

Ignoring endosmosis (electro-osmotic flow): At a pH equal to it’s pI a protein will:

Back 6

stop migrating

Front 7

Considering only the effect of time on electrophoretic separation, the separation of bands ________ with time, and diffusion of bands _______ with time.

Back 7

increases, increases

Front 8

At pH 3 an ampholyte with a pI of 5 will have what charge?

Back 8

Positive

Front 9

In two dimensional electrophoresis what two physical properties are usually used to separate a proteins in a complex mixture (such as serum)?

Back 9

pI and molecular weight

Front 10

If everything else is the same, larger molecules migrate ____________ (faster or slower) than smaller molecules in during electrophoresis?

Back 10

Slower

Front 11

To determine whether an increased alkaline phosphatase result in a teenager is due to bone growth or liver dysfunction, which of the following serum enzymes would provide the best information?

Back 11

Gamma-glutamyltransferase (GGT)

Front 12

The Michaelis constant (Km) of an enzyme represents the substrate concentration where the enzyme is ______.

Back 12

50% of the Vmax

Front 13

The International Unit (IU) for an enzyme is defined as the conversion of ____ of substrate per _____ under standard conditions.

Back 13

One micromole, minute

Front 14

Compared to the determined Km and Vmax for an enzyme without an inhibitor, when a competitive inhibitor is present the values would indicate ___.

Back 14

the Km would be increased and the Vmax would be unchanged

Front 15

A persistently increased Amylase over several days with a normal Lipase would most likely suggest _____.

Back 15

Macroamylasemia

Front 16

The ratio of ALT to AST is usually >1 in which of the following disease states?

Back 16

Viral hepatitis

Front 17

Clinical assays that measure enzyme activity are designed to follow _____.

Back 17

Zero order kinetics

Front 18

Strenuous exercise would result in an increase of which of the following enzymes?

1. Creatine kinase (CK)

2. Alanine aminotransferase (ALT)

3. Cholinesterase (PCHE)

4. Alkaline phosphatase (ALK)

Back 18

Creatine kinase (CK)

Front 19

Which fraction of Alkaline Phosphatase is least stable at 56 degrees?

Back 19

Bone ALK

Front 20

Considering the active site of an enzyme, which of the following statements is not correct?

Back 20

The active site is the location where allosteric inhibitors bind to the enzyme.

Front 21

Which of the following is NOT a branched chain amino acid?

leucine

isoleucine

valine

proline

Back 21

proline

Front 22

Which pair of aminoacidopathies are due to defects in the urea cycle?

Back 22

citrullinemia & argininosuccinic aciduria

Front 23

Which of the following chemicals is used for fixation following serum protein electrophoresis?

Back 23

dilute acetic acid

Front 24

The folding of portions of a polypeptide chain into a regionally stable three dimensional struture which then associates with other areas of stable three dimesional structure within the same polypeptide chain is known as a protein’s _____ structure.

Back 24

secondary

Front 25

Citrullinemia, homocystinuria, phenylketonuria, and maple syrup urine disease are all what type of disorders that are commonly included in newborn screening programs?

Back 25

amino acid disorders

Front 26

What is the physiochemical basis for the visible presence of an "M-spike" or "M-protein" upon serum protein electrophoresis?

Back 26

The M-protein represents a zone of molecularly identical antibodies. That is, each antibody has the same primary amino acid sequence and carries the same antigen recognition site and therefore migrates identically under electrophoresis.

Front 27

This aminoacidopathy has a defect in the metabolism of tyrosine and phenylalanine.

Back 27

alkaptonuria

Front 28

Which of the following cause serum albumin levels to increase?

Back 28

dehydration

Front 29

The overall three-dimensional structure and folding pattern of the complete protein that confers on the protein its specific biological properties is known as the protein’s _____ structure.

Back 29

tertiary

Front 30

What diseases are disorders of branched chain amino acid metabolism?

Back 30

Maple Syrup Urine Disease & isovaleric acidemia

Front 31

Mass Spectrometry measures an ion’s ___________________?

Back 31

mass to charge ratio

Front 32

Which scanning mode allows you to select a specific parent ion and detect ONLY a specific daughter ion produced after collision with the collision gas?

Back 32

Selected Reaction Monitoring

Front 33

You have an unknown sample from a syringe. You suspect that there are drugs in the syringe and you want to know what kind. You have access to a protocol which will ensure that all drugs can be ionized during your experiment. What type of experiment will detect all of the molecules (ions) present inside the syringe?

Back 33

Full Scan

Front 34

What type of ionization utilizes a source of electrons in the form of a filament to which an electric potential is applied?

Back 34

Electron ionization

Front 35

What is meant by “weak ionization” when used to describe Electrospray ionization and Atmospheric Pressure Chemical Ionization?

Back 35

the process of ionization does not lead to the destruction of the molecule into smaller molecular fragment ions

Front 36

Which of the following is a true description of the ionization mechanisms used in GC/MS and LC/MS?

Back 36

Electron Ionization is destructive (i.e. the ions produced almost immediately disintegrate into smaller molecular fragment ions) and is used in GC/MS

Front 37

Which scanning mode allows you to choose and detect ONLY a specific parent ion?

Back 37

Selected Ion Monitoring

Front 38

Which of the following is NOT one of the 4 basic components of a mass spectrometer?

Back 38

Chromatographic separation

Front 39

You have both GC/MS and LC/MS systems in your lab. You have a sample with a drug that has never been seen in your lab before. Which method would you use in order to compare daughter ions to a computerized index “library” of daughter ions of known drugs?

Back 39

GC/MS - Electron Ionization

Front 40

Which of the following is an advantage of immunochemical techniques over techniques using Mass Spectrometry?

Back 40

Speed of the analysis allows high throughput

Front 41

The distinguishing feature of competitive immunoassays is that:

Back 41

The antigen is in excess

Front 42

What is the principal advantage of most homogeneous immunoassays?

Back 42

They can be adapted to any routine chemistry analyzer

Front 43

Which is true of the kinetic interaction of microparticles homogeneous immunoassay?

Back 43

The signal, turbidity, is inversely proportional to the free antigen concentration

Front 44

What is the distinguishing feature of heterogeneous immunoassays?

Back 44

They require separation of bound and free antigen fractions

Front 45

Which of the following is an example of a chemiluminescent reaction?

A. Luciferin/luciferase

B. Luminol/peroxidase

C. Acridinium ester/hydrogen peroxide

D. Galactose/beta-galactosidase Correct

E. A, B, and C are chemiluminescent reactions

Back 45

E. A, B, and C are chemiluminescent reactions

Front 46

In an immunoassay, the function of the label is to

Back 46

Allow an antibody or antigen to be easily detected

Front 47

In comparison to heterogeneous immunoassays involving antibody-coated tubes, methods involving magnetic separation have what distinct advantage?

Back 47

They are faster

Front 48

Which of the following is the best description of the enzyme-multiplied immunoassay technique (EMIT)?

Back 48

Antigen is attached to an enzyme, and when an antibody binds to the enzyme-labeled antigen, enzyme activity is lost

Front 49

Oligonucleotides (short sequences of RNA or DNA) that bind to specific amino acid sequences in proteins are called:

Back 49

Aptamers

Front 50

Which is the best description of a typical enzyme-linked immunosorbent assay (ELISA),

Back 50

Heterogeneous, non-competitive, and 2-site

Front 51

The principal difference between immunoelectrophoresis (IEP) and immunofixation electrophoresis (IFE) is

Back 51

In IEP, serum proteins and antibodies diffuse toward one another, whereas in IFE, serum proteins are stained with specific antibodies

Front 52

Of the following, which is most likely to be susceptible to a high-dose "hook effect"?

Back 52

Serum human chorionic gonadotropin (hCG, used to detect pregnancy and trophoblastic tumors)

Front 53

Select the best description of light scattering:

Back 53

Electromagnetic radiation interacts with molecules or complexes that are about the same size as the wavelength of the radiation, causing the emission of radiation in, mostly, the forward and side directions

Front 54

The "zone of equivalence" refers to:

Back 54

When antigen and antibody concentrations are nearly equal, and cross-linked complexes can form

Front 55

Rate nephelometry is a modification of nephelometric methods that has what advantage?

Back 55

Since it measures the rate at which antigen-antibody complexes form, interference from background scattering, which is mostly constant, can be eliminated.

Front 56

In competitive immunoassays, the % bound antigen is not linear with antigen concentration, but the relationship can be made linear by:

Back 56

Applying the logistic function, the logit transformation, and the log of antigen concentration

Front 57

Which of the following is a property of an antibody-antigen bond?

Back 57

It may involve hydrogen bonds and London forces

Front 58

In precipitation, or particle, methods,

Back 58

No label is involved; the antigen-antibody complex is detected based on its size and/or solubility

Front 59

The most common way that HAMA interferes with immunoassays is by:

Back 59

Binding to capture and signal antibodies to form a "bridge" in the absence of antigen

Front 60

The principal advantage of electroimmunodiffusion, or "rocket electrophoresis," compared to single radial immunodiffusion, is

Back 60

Electroimmunodiffusion is faster than radial immunodiffusion

Front 61

A pH electrode includes what type of ion selective membrane?

Back 61

Glass

Front 62

Why does the "sodium error" occur in indirect potentiometric methods?

Back 62

Because proteins and lipids normally exclude water from about 5% of the total volume of serum or plasma

Front 63

The principal difference between potentiometry and voltammetry (or amperometry) is:

Back 63

Potentiometry involves measurement of potential without current flow, whereas voltammetry involves measurement of current when an external potential is applied

Front 64

What fraction of total calcium concentration in serum does a calcium ion selective electrode measure?

Back 64

Only the unbound ("ionized," or "free") fraction

Front 65

A carbon dioxide gas (pCO2) electrode:

Back 65

Is a pH electrode separated from the sample by a gas-permeable membrane

Front 66

Although it is usually ignored, the "sodium error" can be significant when:

Back 66

Protein or lipids are highly elevated

Front 67

Which type of ion selective electrode is ordinarily used to measure chloride?

Back 67

silver chloride/silver sulfide solid state electrode

Front 68

One way to eliminate the "sodium error" is to:

Back 68

Use a direct potentiometric method

Front 69

In voltammetric methods, the concentration of the electrochemically active species (analyte) is proportional to the

Back 69

Limiting current

Front 70

Potassium is ordinarily measured using a:

Back 70

Valinomycin electrode

Front 71

Oxidation and reduction (or, redox) reactions involve:

Back 71

Transfer of electrons from one atom or molecule to another

Front 72

In an ion selective electrode, changes in potential are detected when the analyte ions interact with:

Back 72

The ion-selective membrane

Front 73

The relationship between the electrochemical potential for a reaction, the concentrations of reduced and oxidized species, and the temperature, is established by:

Back 73

The Nernst equation

Front 74

Why is the electrochemical activity of an element or compound often less than its total concentration?

Back 74

Some of the element or compound may be bound to other compounds, and therefore does not interact with the electrode

Front 75

When an element or compound is oxidized,

Back 75

Its charge becomes more positive

Front 76

Dilution of a specimen prior to electrochemical measurements serves to:

Back 76

Make the activity coefficient closer to unity

Front 77

By convention, all standard electrochemical potentials are expressed relative to:

Back 77

The standard hydrogen electrode

Front 78

What is the purpose of a reference electrode

Back 78

Reference electrodes provide a stable reference potential against which the potential of electrochemical reactions can be measured

Front 79

If zinc and copper electrodes are attached in an electrical circuit, electrons will flow from the zinc to the copper electrode because:

Back 79

Copper is more electronegative than zinc

Front 80

In an electrochemical cell, cations (positive charges) are attracted to the:

Back 80

Cathode

Front 81

Which is the most common method for measuring serum total protein in clinical laboratories?

Back 81

The biuret method

Front 82

Direct photometric measurement of protein is based on:

Back 82

UV absorption by tyrosine and tryptophan residues in proteins

Front 83

Cholesterol is often measured using an enzymatic method. In these methods, what end-product is usually measured?

Back 83

Hydrogen peroxide (H2O2)

Front 84

The enzyme cofactor nicotinamide adenine dinucleotide is useful for monitoring dehydrogenation reactions because:

Back 84

It's oxidized and reduced forms have different UV absorption spectra

Front 85

The reference method for measuring total protein is:

Back 85

The Kjeldahl method

Front 86

Which of the following can result in an abnormally high serum protein concentration?

Back 86

B-cell malignancies such as multiple myeloma

Front 87

The key difference between atomic absorption and atomic emission methods is:

Back 87

In atomic absorption, excitation of electrons is by radiation, whereas in atomic emission, excitation is thermal

Front 88

Why isn't total protein in serum always measured by absorbance at 280 nm?

Back 88

There are many non-protein substances in serum that also absorb at 280 nm

Front 89

In the biuret method for measuring protein, the function of sodium potassium tartrate is to

Back 89

Stabilize Cu++ (cupric) ions

Front 90

Atomic absorption methods are typically used to measure:

Back 90

Metallic elements vaporized in a flame

Front 91

The velocity at which electromagnetic radiation moves through a vacuum is:

Back 91

The speed of light (c)

Front 92

The energy of electromagnetic radiation is:

Back 92

Proportional to frequency and inversely proportional to wavelength

Front 93

Which of the following has the shortest wavelength?

Back 93

Ultraviolet radiation

Front 94

The energy of ultraviolet (UV) and visible electromagnetic radiation corresponds to:

Back 94

Electronic transitions between bonding, non-bonding, and anti-bonding outer-shell molecular orbitals

Front 95

What three factors determine Beer's law absorbance?

Back 95

Concentration, pathlength, and the molar absorptivity constant (or extinction coefficient

Front 96

If the transmittance is 30%, then the absorbance is:

Back 96

0.523

Front 97

The relationship between absorbance (A) and % transmittance (T) is:

Back 97

A = 2 - log(%T)

Front 98

Fluorescence differs from emission in what respect?

Back 98

Fluorescence involves non-radiative energy loss by vibrational relaxation; emission does not

Front 99

Spectrophotometric methods are based on:

Back 99

Interaction of electromagnetic radiation with matter

Front 100

In electromagnetic radiation, what is the relationship between wavelength and frequency?

Back 100

They are inversely proportional