91344 MEDICAL and DIAGNOSTIC BIOCHEMISTRY. REVISION SESSION . Q.1. In a serum ur
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Question
91344 MEDICAL and DIAGNOSTIC BIOCHEMISTRY.
REVISION SESSION .
Q.1. In a serum urea estimation using diacetyl monoxime reagent, the procedure is as follows :
Protein Pptation Step :
Mix the following : 0.1 mL serum
0.1 mL 0.5 M NaOH
3.8 mL Zn SO4 / Na2 SO4 pptation reagent
Stand and centrifuge. Separate supernatant.
Colour Development Step :
Stock Standard urea : 0.6 g/ L urea = 10.0 mM
Working Standard : Prepare by diluting 2.0 mL Stock Standard to 100 mL . This corresponds to 8.0 mmol/ L serum.
Take 1.0 mL of sample supernatant , or Working Standard, mix with 3.0 mL Diacetylmonoxime reagent in a test tube. Stand 20 minutes and read absorbances.
(a). Prove that the Working Standard corresponds to 8.0 mmol/ L serum.
(b). Calculate the concentration of an unknown serum sample which gave an absorbance of 0.180, when the Standard gave an absorbance of 0.240.
Q.2.
a. What are the three processes involved in urine formation and where do they occur?
b. Give examples of what can be normally found in the filtrate from which urine is formed.
c. Give examples of what is normally excluded from the filtrate.
Q.3.
a. What is meant by renal clearance?
b. What is it its clinical significance?
c. Which of the following substances would be useful in studies of renal clearance and why/why not?
i. Proteins like albumin:
ii. Glucose
iii. Creatinine
Q. 4.
Physiologically MetHb is constantly being formed within erythrocytes because of spontaneous oxidation of haemoglobin but is prevented from accumulating within the red cells by the reduction of oxidised heme. What is the mechanism?
Q. 5
a. What is methaemalbumin?
b. What is the Soret absorbance peak of methaemalbumin?
c.Under what circumstances will increased levels of methaemalbumin be detected in a patient's blood?
Q.6.
Outline the steps a clinical biochemist would perform to investigate a paraprotein.
Q.7.
a. Define hyponatraemia
b. What is the principal mechanism behind hyponatraemia?
c. The most significant consequence of hyponatraemia is hypovolaemia. What is the mechanism behind this and in turn the major consequences of this?
Q. 8
a. What is the basis for the anion gap?
b. A man turns up at casualty after a heavy bout of drinking. In the course of the examination his plasma electrolyte levels are taken: Sodium: 140 mM, Potassium 4.9 mM, chloride 100 mM and bicarbonate 5 mM, blood pH of < 7.35
Calculate the anion gap and comment on the finding.(normal anion gap 14- 18 mM)
Q. 9.
How is normal ketone metabolism disrupted in uncontrolled diabetes mellitus?
Q. 10.
The interplay of what two mechanisms leads to the development of Type II or Non Insulin Dependent Diabetes Mellitus?
Q.11.
What are the three main methods used to establish Reference Intervals in diagnostic biochemistry? What factor is the most important in making the decision which method to apply?
Q.12.
Reference Intervals are difficult to establish for analytes that are not normally distributed. Identify one method, which could be used to establish Reference Intervals in non-normally distributed populations.
Q.13.
In dynamic testing the absolute concentration of a given substance may be less important than the biological response to a specific challenge. Give an example one
such dynamic test and identify which factor is the most important in establishing an appropriate Reference Interval.
Q.14.
What is the difference between Quality Management, Quality Assurance and Quality Control? Why are all three equally important in the “Total Quality” concept.
Q. 15
What (different) Quality Control procedures are required when using automated as compared to manual methodology?
Q. 16.
What are the 2, 3, 4, 5 and 6 sigma controls? How would current methodology need to be improved to move beyond the present 2-sigma control to 5 and 6 sigma control?
Q.17.
In liver disease indicate which alternative is correct:
1. In prehepatic jaundice bilirubin or urobilinogen is detected in urine
2. In post hepaticjJaundice bilirubin or urobilinogen is detected in urine
3. Vitamin K deficiency is not encountered in prehapatic orpost hepatic jaundice
4. Prothrombin time is increased ordecreased in liver disorders
5. Serum total cholesterol level increases ordecreases in obstructive jaundice
6. ALP or ALT rises in obstructive liver disorders
7. AST or ALT would rise more in alcoholism
8. Pale or dark coloured stools are observed in haemolytic jaundice
9. Pale or dark stools are observed in obstructive jaundice
10. Indicect or direct positive Van der Bergh reaction is observed in post hepatic jaundice.
Q.18
In a lactate dehydrogenase (LD) assay, 0.1 mL serum is added to 2.4 mL phosphate buffer containing NADH, and the rate of change of absorbance is monitored in a 1.0 cm pathlength cuvette at 340 nm.
For one serum sample, the result obtained was -0.045 absorbance units per minute.
Calculate the LD activity of this serum, in U/ L serum.
( For NADH at 340 nm, = 6.22 x 103 L.mol-1.cm-1).
Q.19.
(a) What problems are encountered with the substrate -glutamyl-p-nitroanilide in the measurement of -glutamyl transferase, and what alternative procedures have been developed ?
(b) Describe the immunoprecipitation technique for measuring LD isoenzymes.
Q 20
What is Delta Bilirubin, and what is its clinical significance ?
Q. 21
(a)
You are supplied with 500 mL of a solution of 0.218 M NaOH. How would you adjust the concentration to 0.200 M ?
(b)
A modification of the uric acid method of Brown is carried out as follows :-
Protein Precipitation : Mix 0.1 mL serum with 4.7 mL water and 0.2 mL 10% sodium tungstate solution. Stand 15 minutes and centrifuge; separate supernatant.
Standards : Stock Uric Acid Standard = 0.060 M (= 60 mmol/ L) uric acid in water.
Working Standard: Dilute 1.0 mL Stock Standard to 500 mL with water.
Colour Development : Take 2.0 mL supernatant or 2.0 mL Working Standard and add 3.0 mL colour reagent. Stand for 10 minutes and read absorbances at 650 nm..
i. What is the actual uric acid concentration of the Working Standard, in mmol/ L solution ?
ii. To what uric acid concentration, expressed as mmol/ L serum does the Working Standard correspond ?
iii. Write an expression for the calculation of the uric acid concentration of an
unknown serum sample, in mmol/ L serum, based on the absorbance obtained from the unknown serum Aunk, and the absorbance obtained from the Working Std Astd.
Q. 22
a. What clinical conditions contribute to high bilirubin values?
b. Explain why indirect bilirubin reacts with daizotised sulphanilic acid in aqueous solution at an alkaline pH without accelerators or miscible solvents even though the latter are required to bring about reaction in aqueous solution in an acid pH.
Explanation / Answer
2a. ANS: Urine is one of the body's waste products. It is primarily composed of water and urea. Urine formation occurs in the kidney in three stages: filtration, reabsorption, and secretion.
2b. ANS: Urine is liquid excrement consisting of water, salts, and urea, which is made in the kidneys then released through the urethra.
2c. ANS: The proteins excluded from filtrate, because the proteins are too big to fit through spilt pores, proteins ultimately return water to the plasma
3a. ANS: The rate at which a particular chemical is removed from the plasma indicates kidney efficiency. This rate of removal is called renal clearance.
3b. ANS: Tests of renal clearance can detect glomerular damage or judge the progress of renal disease.
3c. ANS: Inulin is widely used for this test; it is because the inulin passes freely through the glomerular membranes, so that its concentration in the glomerular filtrate equals that of the plasma. The rate at which it appears in the urine can be used to calculate the rate of glomerular filtration.
4. ANS: Methemoglobin is a form of hemoglobin that contains the ferric [Fe3+] form of iron. The affinity for oxygen of ferric iron is impaired. The binding of oxygen to methemoglobin results in an increased affinity for oxygen in the remaining heme sites that are in ferrous state within the same tetrameric hemoglobin unit. This leads to an overall reduced ability of the red blood cell to release oxygen to tissues.
5a. ANS: Methaemalbumin is a chemical complex of the pigment portion of haemoglobin (haem) with the plasma protein albumin. It is formed in the blood in conditions in which red blood cells are destroyed and free haemoglobin is released into the plasma.
5b. ANS: Methaemalbumin may be formed after intravascular haemolysis, haemorrhagic pancreatitis. Methaemalbumin has a Soret absorbance peak at 408 nm. This peak overlaps the 415 nm wavelength available on Hitachi analysers
5c. ANS: The level of methaemalbumin in the plasma may be raised above the upper limit of the normal range of 5.5 mg % in occasional cases of gastrointestinal bleeding and soft tissue trauma.
Please remind this note: Answering to many questions is against to chegg rule, so I am answering 2 to 5 questions.
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