Question 1

Urea:&#10;A) biosynthesis is carried out exclusively in the renal system.&#10;B) is 100% reabsorbed (thus not excreted)by the kidney.&#10;C) is decreased in plasma by a variety of renal diseases.&#10;D) concentration in plasma is increased by a high-protein diet.

Accepted Answer

Urea is a waste product formed from the breakdown of proteins and amino acids in the liver. It is then filtered by the kidneys and excreted in the urine. A high-protein diet increases the amount of urea formed in the liver, leading to an increase in its concentration in plasma. Therefore, choice D is the correct answer. Choices A and B are incorrect as urea is synthesized in the liver and only partially reabsorbed by the kidneys. Choice C is also incorrect as renal diseases can result in an increase in urea concentration in plasma.

Question 2

Uricase is used in the assay of uric acid to:&#10;A) decarboxylate uric acid to form tungsten blue.&#10;B) oxidize uric acid to form allantoin.&#10;C) reduce uric acid to form allantoin.&#10;D) reduce uric acid to form tungsten blue.

Accepted Answer

Uricase is an enzyme that oxidizes uric acid to allantoin. Therefore, the correct answer is B.

Question 3

Why do values obtained with the Jaffe reactions for creatinine measurement overestimate creatinine concentration by ~20%?&#10;A) The components of the reaction mixture often continue to react at endpoint and synthesize excess creatinine.&#10;B) The rate of Jaffe complex formation is temperature dependent,and excess heat formed by the reaction leads to increased absorptivity and falsely increased creatinine value.&#10;C) Noncreatinine chromogens in the reaction that react with the picrate in the end-point Jaffe methods overestimate true plasma creatinine concentration.&#10;D) Hydroxide concentrations above 0.5 mmol/L produce a decreased degradation of the Jaffe complex.

Accepted Answer

Noncreatinine chromogens in the reaction that react with the picrate in the end-point Jaffe methods overestimate true plasma creatinine concentration. These noncreatinine chromogens can be present in urine due to medications or other substances in the diet or environment. This can lead to a falsely elevated creatinine measurement.

Question 4

Creatininase reactions for creatinine assessment:&#10;A) yield sarcosine and urea.&#10;B) require the addition of potassium ferricyanide to reduce interference.&#10;C) catalyze the conversion of creatinine to creatine.&#10;D) catalyze the conversion of creatinine to N-methylhydantoin and ammonia.

Accepted Answer

Creatininase catalyzes the conversion of creatinine to creatine, which is then further broken down in subsequent reactions for assessment.

Question 5

Creatinine clearance is used to assess the _____ of a patient.&#10;A) glomerular filtration rate&#10;B) creatine concentration&#10;C) renal threshold&#10;D) renal hormonal function

Accepted Answer

Creatinine clearance measures the rate at which creatinine is filtered from the blood by the kidneys, which reflects the glomerular filtration rate (GFR). GFR is used to assess the overall function of the kidneys. This test is commonly used to diagnose and monitor chronic kidney disease.

Question 6

In the measurement of urea,urea is initially hydrolyzed by urease to form ammonium ions.This assay combined with the spectrophotometric measurement of the resulting ammonia is referred to as the:&#10;A) ammonia-selective electrode method.&#10;B) Berthelot reaction.&#10;C) Jaffe reaction.&#10;D) urea method.

Accepted Answer

The mentioned method involves the hydrolysis of urea by urease to form ammonium ions which are then measured using spectrophotometric measurement to determine ammonia. This method is commonly known as the Berthelot reaction. Option A is incorrect as it refers to a different method that measures ammonia using a selective electrode. The Jaffe reaction (option C) is a colorimetric method performed on serum or plasma to measure creatinine levels, not urea. Option D is too generic and does not refer to a specific method.

Question 7

Which one of the following statements regarding creatinine is correct?&#10;A) Most intraindividual variation in serum creatinine is due to muscle mass.&#10;B) Serum creatinine levels are not affected by renal disease.&#10;C) Creatinine production increases when serum creatinine is elevated.&#10;D) Creatinine is completely reabsorbed (not excreted)by the renal tubules.

Accepted Answer

Serum creatinine levels are primarily influenced by muscle mass, hence the intraindividual variation in serum creatinine is mainly due to muscle mass. B is incorrect as renal disease can increase or decrease serum creatinine levels depending on the severity of the disease. C is incorrect as elevated serum creatinine levels indicate decreased renal function and therefore decreased creatinine production. D is incorrect as creatinine is filtered and excreted by the renal tubules.

Question 8

Which of the following is the primary reagent used in the Jaffe reaction for creatinine?&#10;A) Alkaline copper sulfate&#10;B) Phosphotungstic acid&#10;C) Alkaline picric acid&#10;D) Diacetyl monoxime

Accepted Answer

The primary reagent used in the Jaffe reaction for creatinine is alkaline picric acid. The Jaffe reaction involves the formation of a yellow-orange complex between creatinine and picric acid in an alkaline solution. The intensity of the color is proportional to the amount of creatinine present in the sample.

Question 9

Why does persistently acidic urine lead to formation of uric acid renal stones?&#10;A) Uric acid has a pKa of 5.57,which makes it insoluble in acidic solutions.&#10;B) At a pH of 10,uric acid is insoluble and aggregates to form stones.&#10;C) Elevated urine purines cause uric acid crystals to aggregate and form stones.&#10;D) Supersaturation of acidic urine causes calcium to form complexes with uric acid,which is the initial step in stone formation.

Accepted Answer

Uric acid has a pKa of 5.57, which means it is insoluble in acidic solutions. Therefore, persistently acidic urine would cause uric acid to remain insoluble and crystallize, leading to the formation of renal stones.

Question 10

A practicing physician at a university student healthcare facility often recommends to student patients that they take large doses of vitamin C (ascorbic acid)to fend off colds during the semester.As director of the chemistry laboratory that serves this facility,you notice a trend in that many of this physician's students' serum creatinine levels are unusually high.You are currently using a type of analysis based on the Jaffe reaction.What might be the cause of the elevated values?

A) High doses of ascorbic acid cause increased hepatic synthesis of bilirubin,which interferes with the enzymes used in the assay.
B) Elevated ascorbic acid in serum produces a Jaffe-like chromogen in this analysis that can be interpreted as increased serum creatinine.
C) It may be that this physician's patients all are exhibiting increased muscle breakdown.
D) The ketones and ketoacids produced from the breakdown of creatinine in the students' serum are interfering with the development of the color reaction.

Accepted Answer

Elevated levels of ascorbic acid in the serum can interfere with the Jaffe reaction, leading to a Jaffe-like chromogen that appears to be increased serum creatinine. This interference can result in falsely elevated serum creatinine levels.

Question 11

All of the following conditions are associated with hyperuricemia except:&#10;A) excessive cell turnover as in malignancy treated with chemotherapy.&#10;B) deficiency of hypoxanthine-guanine phosphoribosyl transferase.&#10;C) preeclampsia toxemia.&#10;D) severe hepatocellular disease.

Accepted Answer

The answer of All of the following conditions are associated...

Question 12

Urea is produced from:&#10;A) catabolism of purine nucleosides.&#10;B) phosphorylation of creatine in muscle.&#10;C) reduction of bilirubin.&#10;D) catabolism of proteins and amino acids.

Accepted Answer

The answer of Urea is produced from:&#10;A) catabolism of purine...

Question 13

Primary gout is distinguished from secondary gout by:&#10;A) decreased renal excretion (increased renal retention)of uric acid.&#10;B) its polygenic basis.&#10;C) having increased dietary intake of purines.&#10;D) the increased catabolism of purines due to chemotherapy.

Accepted Answer

The answer of Primary gout is distinguished from secondary gout...

Question 14

A hemolyzed serum sample from an individual is assayed for creatinine and a result is obtained that is decreased compared to the normal reference interval.If this individual has a normal glomerular filtration rate,which one of the following statements is true?

A) The individual's diet contains high levels of protein.
B) The individual must be receiving chemotherapy.
C) The assay must be subject to interference from bilirubin.
D) The assay must be subject to interference from ketones.

Accepted Answer

The answer of A hemolyzed serum sample from an individual...

Question 15

The major nonprotein nitrogen degradation product of endogenous purines is:&#10;A) urea.&#10;B) creatinine.&#10;C) uric acid.&#10;D) ammonia.

Accepted Answer

The answer of The major nonprotein nitrogen degradation product of...

Question 16

Plasma urea concentration:&#10;A) is a more reliable indicator of renal function than creatinine.&#10;B) can increase because of decreased renal perfusion.&#10;C) is decreased in intrinsic renal failure.&#10;D) is not affected by diet.

Accepted Answer

The answer of Plasma urea concentration:&#10;A) is a more reliable...

Question 17

An individual's laboratory results indicate increased serum creatinine and urea values,and his physician's diagnosis indicates a postrenal obstruction.What would the glomerular filtration rate in this individual likely be?

A) Decreased
B) Increased
C) No change

Accepted Answer

The answer of An individual's laboratory results indicate increased serum...

Deck 21: Kidney Function Test-Screatinine, Urea, and Uric Acid