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Proteins, Electrophoresis And Lipids – Questions & Answers (100% Correct)
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Proteins, Electrophoresis And Lipids – Questions &Answers (100% Correct)
Kjeldahl's procedure for total protein is based upon the premise that:
A. Proteins are negatively charged
B. The pKa of proteins is the same
C. The nitrogen content of proteins is constant
D. Proteins have similar tyrosine and tryptophan content Right Ans - C
Kjeldahl's method measures the nitrogen content of proteins as ammonium
ion by back titration following oxidation of proteins by sulfuric acid and heat.
It assumes that proteins average 16% nitrogen by weight. Protein in grams
per deciliter is calculated by multiplying protein nitrogen by 6.25. The
Kjeldahl method is a reference method for total protein that is used to assign a
protein assay value to calibrators.
Harr, Robert R. Medical Laboratory Science Review (Page 246). F.A. Davis
Company. Kindle Edition.
Upon which principle is the biuret method based?
A. The reaction of phenolic groups with CuIISO4
B. Coordinate bonds between Cu+2 and carbonyl and imine groups of peptide
bonds.
C. The protein error of indicator effect producing color when dyes bind
protein
D. The reaction of phosphomolybdic acid with protein Right Ans - B
Biuret is a compound with two carbonyl groups and three amino groups and
forms coordinate bonds with Cu +2 in the same manner as does protein.
Therefore, proteins and peptides are both measured in the biuret reaction.
The biuret reagent consists of an alkaline solution of copper II sulfate.
Tartrate salts are added to keep the copper in solution and prevent turbidity.
Potassium iodide prevents autoreduction of Cu +2.
Harr, Robert R. Medical Laboratory Science Review (Page 246). F.A. Davis
Company. Kindle Edition.
Which statement about the biuret reaction for total protein is true?
A. It is sensitive to protein levels below 0.1 mg/dL
,B. It is suitable for urine, exudates, and transudates
C. Polypeptides and compounds with repeating imine groups react
D. Hemolysis will not interfere Right Ans - C
The biuret reaction is not sensitive to protein levels below 0.1 g/dL and,
therefore, is not sensitive enough for assays of total protein in CSF, urine, or
transudates. Slight hemolysis does not cause falsely high results, if the
absorbance of the Cu +2-protein complexes is measured bichromatically.
However, frankly hemolyzed samples contain sufficient globin to cause
positive interference. The reagent reacts with peptides containing at least two
peptide bonds, but due to the high concentration of proteins in plasma
relative to peptides present this reactivity causes insignificant bias.
Harr, Robert R. Medical Laboratory Science Review (Page 246). F.A. Davis
Company. Kindle Edition.
Which of the following protein methods has the highest analytical sensitivity?
A. Refractometry
B. Folin-Lowry
C. Turbidimetry
D. Direct ultraviolet absorption Right Ans - B
The Folin-Lowry (Lowry's) method uses both biuret reagent and
phosphotungstic and molybdic acids to oxidize the aromatic side groups on
proteins. The acids oxidize the phenolic rings of tyrosine and tryptophan.
These, in turn, reduce the Cu +2 in the biuret reagent, increasing sensitivity
about 100-fold.
Harr, Robert R. Medical Laboratory Science Review (Page 246). F.A. Davis
Company. Kindle Edition.
Which of the following statements regarding proteins is true?
A. Total protein and albumin are about 10% higher in ambulatory patients
B. Plasma total protein is about 20% higher than serum levels
C. Albumin normally accounts for about one-third of the cerebrospinal fluid
total protein
D. Transudative serous fluid protein is about two-thirds of the serum total
protein Right Ans - A
Water pools in the vascular bed in nonambulatory patients, lowering the total
protein, albumin, hematocrit, and calcium. Plasma levels of total protein are
0.2-0.4 g/dL higher than serum (about 5%) owing to fibrinogen.
, Cerebrospinal fluid albumin levels are normally 10-30 mg/dL, which is
approximately two-thirds of the CSF total protein. Transudates have a total
protein below 3.0 g/dL and less than 50% of the serum total protein.
Harr, Robert R. Medical Laboratory Science Review (Page 247). F.A. Davis
Company. Kindle Edition.
Hyperalbuminemia is caused by:
A. Dehydration syndromes
B. Liver disease
C. Burns
D. Gastroenteropathy Right Ans - A
A high serum albumin level is caused only by dehydration or administration of
albumin. Liver disease, burns, gastroenteropathy, nephrosis, starvation, and
malignancy cause hypoalbuminemia.
Harr, Robert R. Medical Laboratory Science Review (Page 247). F.A. Davis
Company. Kindle Edition.
High serum total protein but low albumin is usually seen in:
A. Multiple myeloma
B. Hepatic cirrhosis
C. Glomerulonephritis
D. Nephrotic syndrome Right Ans - A
In multiple myeloma, synthesis of large quantities of monoclonal
immunoglobulin by plasma cells often results in decreased synthesis of
albumin. In glomerulonephritis and nephrotic syndrome, both total protein
and albumin are low owing to loss of proteins through the glomeruli. In
hepatic cirrhosis, decreased hepatic production of protein results in low total
protein and albumin.
Harr, Robert R. Medical Laboratory Science Review (Page 247). F.A. Davis
Company. Kindle Edition.
Which of the following conditions is most commonly associated with an
elevated level of total protein?
A. Glomerular disease
B. Starvation
C. Liver failure
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