Tuesday, November 13, 2012

hemoglobin


Q. What are the salient structural features of hemoglobin molecule?
A. Hb has four subunits, two alpha and two beta
units. It contains four iron atoms.

Q. How many molecules of oxygen can bind with hemoglobin?
A. Hb can bind four molecules of oxygen.

Q. 100 ml of blood can carry how much oxygen?
A. 20 ml.

Q. What is Bohr effect? 
A. The influence of pH and pCO2 to facilitate oxygenation of Hb in the lungs and deoxygenation
at the tissues is known as the Bohr effect.

Q. What is chloride shift?
A. When CO2 is taken up, chloride ions from the plasma would enter. This is called chloride shift
or Hamburger effect.

Q. Hemoglobin carries how much CO2? 
A. Seventy five percent as isohydric transport and 15% as carbamino hemoglobin.

Q. What are the forms in which carbon dioxide is transported? 
A. Dissolved form, isohydric transport, and carbamino hemoglobin.

Q. What is isohydric transport of carbon dioxide?
A. There is minimum change in pH during the transport.

Q. How this is effected? 
A. The H+ ions are buffered by the deoxy-Hb.

Q. Which will decrease the affinity of hemoglobin for oxygen?
A. 2,3-BPG level.

Q. What is the structural difference between HbA and HbF?
A. HbA has two alpha and two beta chains, but HbF has two alpha and two gamma chains.

Q. What are the laboratory tests to identify HbF?
A. HbF moves slower than HbA on electrophoresis, HbF is alkali resistant.

Q. What is the physiological significance of HbF?
A. Oxygen affinity is more for HbF than HbA. HbF is seen in foetal circulation.


Q. What is the clinical significance of HbF?
A. It is seen in adults in hemoglobinopathies and thalassemias.

Q. Why carbon monoxide becomes a poison?
A. Hb has more affinity to carbon monoxide than oxygen.

Q. What is the treatment for carbon monoxide poison? 
A. Hyperbaric oxygen.

Q. Met-hemoglobin is found in which conditions?
A. Ingestion of nitrites, presence of HbM, GPD deficiency.

Q. What is met-hemoglobin? 
A. Hemoglobin in which iron is in ferric state.

Q. What is the defect of met-hemoglobin?
A. It cannot release oxygen in tissues.

Q. What is the reagent used for colourimetric estimation of hemoglobin? 
A. Drabkin’s reagent, to convert Hb to cyanmethemoglobin.

Q. What is hemoglobin S? 
A. The glutamic acid in the 6th position of beta chain of HbA is changed to valine in HbS.


Q. What is the cause for sickle cell anemia?
A. Solubility of deoxy HbS is lower than deoxy HbA,so HbS is precipitated intracellularly, leading to
sickle shape of RBC.

Q. How HbS is identified?
A. HbS is slower moving on electrophoresis than HbA.

Q. What is sickle cell trait?
A. Heterozygous (AS) condition, one allele is normal, the other is abnormal, so half of Hb molecules are normal, and half abnormal.

Q. What is its clinical significance?
A. Sickle cell trait persons will not have any disease manifestations, usually. But, at higher altitudes,
hypoxia may cause manifestation of the disease.Chronic lung disorders may also produce
hypoxia-induced sickling in HbS trait.


------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
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