Hemoglobin, Hemoglobin synthesis, Porphyrias PDF

Part One: Simple MCQs 1. What is the normal concentration of hemoglobin in adult males? a) 10-12 g/dl b) 12-14 g/dl c) 13.5-16.5 g/dl d) 17-19 g/dl 2. Which type of hemoglobin constitutes the majority of adult hemoglobin? a) HbA b) HbA2 c) HbF d) HbA1c 3. How many globin chains are present in a...

Part One: Simple MCQs 1. What is the normal concentration of hemoglobin in adult males? a) 10-12 g/dl b) 12-14 g/dl c) 13.5-16.5 g/dl d) 17-19 g/dl 2. Which type of hemoglobin constitutes the majority of adult hemoglobin? a) HbA b) HbA2 c) HbF d) HbA1c 3. How many globin chains are present in a hemoglobin molecule? a) 2 b) 4 c) 6 d) 8 4. What is the function of hemoglobin? a) Iron storage b) Oxygen and carbon dioxide transport c) Blood clotting d) Immune defense 5. Which of the following is NOT a hemoprotein? a) Hemoglobin b) Myoglobin c) Cytochrome P450 d) Albumin 6. Where does the majority of heme synthesis occur? a) Liver and spleen b) Bone marrow and liver c) Kidneys and intestines d) Brain and heart 7. Which cellular compartments are involved in heme synthesis? a) Cytosol only b) Mitochondria only c) Both cytosol and mitochondria d) Nucleus and endoplasmic reticulum 8. What are the starting materials for the synthesis of ALA (the first step in heme synthesis)? a) Glycine and glucose b) Succinyl CoA and alanine c) Succinyl CoA and glycine d) Acetyl CoA and glutamate 9. Which enzyme catalyzes the rate-limiting step in heme synthesis? a) ALA dehydratase b) Ferrochelatase c) ALA synthase d) Porphobilinogen deaminase 10. What is the effect of lead poisoning on heme synthesis? a) It stimulates heme synthesis b) It inhibits ferrochelatase and ALA dehydratase c) It increases the excretion of heme in urine d) It has no effect on heme synthesis Answer Guide Part One 1. c 2. a 3. b 4. b 5. d 6. b 7. c 8. c 9. c 10. b Part Two: Complex MCQs 1. Explain the structural organization of adult hemoglobin (HbA). a) It is a dimer composed of two globin chains and two heme groups b) It is a tetramer composed of four globin chains and four heme groups c) It is a monomer composed of one globin chain and one heme group d) It is a hexamer composed of six globin chains and six heme groups 2. What is the role of iron in the heme molecule? a) It binds to oxygen and carbon dioxide b) It stabilizes the porphyrin ring structure c) It acts as a cofactor for enzymes involved in heme synthesis d) It regulates the rate of heme synthesis 3. Describe the key regulatory mechanism of heme synthesis. a) Feedback inhibition of ALA synthase by heme and hemin b) Stimulation of ALA synthase by glucose and steroids c) Regulation of iron absorption in the intestines d) Activation of ferrochelatase by lead 4. What are porphyrias, and what causes them? a) They are disorders characterized by decreased heme synthesis due to iron deficiency b) They are disorders characterized by increased heme synthesis due to enzyme overactivity c) They are disorders characterized by the accumulation and increased excretion of porphyrins or porphyrin precursors due to enzyme deficiencies in the heme synthesis pathway d) They are disorders characterized by the inability to transport oxygen due to hemoglobin mutations 5. Differentiate between erythropoietic porphyria and hepatic porphyria. a) Erythropoietic porphyria affects the liver, while hepatic porphyria affects the bone marrow b) Erythropoietic porphyria is characterized by abdominal pain and neuropsychiatric symptoms, while hepatic porphyria is characterized by photosensitivity and skin rash c) Erythropoietic porphyria is caused by enzyme deficiencies in the bone marrow, while hepatic porphyria is caused by enzyme deficiencies in the liver d) Both erythropoietic porphyria and hepatic porphyria have the same clinical manifestations 6. How does lead poisoning interfere with heme synthesis? a) It inhibits the uptake of iron by red blood cells b) It competes with iron for binding to protoporphyrin IX c) It inhibits ferrochelatase and ALA dehydratase, leading to the accumulation of protoporphyrin IX and ALA d) It stimulates the breakdown of heme 7. What are the clinical manifestations of porphyrias? a) Photosensitivity, skin rash, abdominal pain, neuropsychiatric symptoms, hypertension b) Anemia, jaundice, splenomegaly, hepatomegaly c) Increased appetite, weight gain, fatigue, muscle weakness d) None of the above 8. How is the diagnosis of porphyrias made? a) By measuring blood glucose levels b) By measuring the levels of porphobilinogen and other heme synthesis metabolites in urine, plasma, and feces c) By performing a bone marrow biopsy d) By genetic testing only 9. What is the difference between heme and hemin? a) Heme contains ferrous iron (Fe2+), while hemin contains ferric iron (Fe3+) b) Heme is a component of hemoglobin, while hemin is a component of myoglobin c) Heme is synthesized in the cytosol, while hemin is synthesized in the mitochondria d) There is no difference between heme and hemin 10. How is heme synthesis regulated in the liver compared to erythroid cells? a) Heme synthesis is not regulated in either tissue b) Heme synthesis is regulated by iron availability in both tissues c) Heme synthesis is regulated by heme and hemin in the liver (ALAS1) and by iron availability in erythroid cells (ALAS2) d) Heme synthesis is regulated by glucose and steroids in the liver and by hypoxia and erythropoietin in erythroid cells 11. What is the function of cytochrome P450? a) Oxygen transport b) Drug metabolism and detoxification c) Heme degradation d) Energy production 12. Why is the first step in heme synthesis considered the key regulatory step? a) It is the only step that occurs in the mitochondria b) It is the slowest step in the pathway c) It is the step that incorporates iron into the porphyrin ring d) It is the step catalyzed by ALA synthase, which is subject to feedback inhibition and other regulatory mechanisms 13. What is the role of ALA dehydratase in heme synthesis? a) It catalyzes the conversion of succinyl CoA and glycine to ALA b) It catalyzes the conversion of ALA to porphobilinogen c) It catalyzes the incorporation of iron into protoporphyrin IX d) It is not involved in heme synthesis 14. A patient presents with photosensitivity and skin rash. Which type of porphyria is most likely? a) Acute intermittent porphyria b) Erythropoietic porphyria c) Lead poisoning d) Chronic alcohol liver disease 15. Explain why glucose inhibits heme synthesis in the liver. a) Glucose provides an alternative energy source, reducing the need for heme-containing cytochromes in oxidative phosphorylation b) Glucose directly inhibits the activity of ALA synthase c) Glucose promotes the excretion of heme d) Glucose has no effect on heme synthesis Answer Guide Part Two 1. b 2. a 3. a 4. c 5. c 6. c 7. a 8. b 9. a 10. c 11. b 12. d 13. b 14. b 15. a Done 8) Rate limiting Step in Porphyrin Synthesis is a. δ-Amino Levulinic Acid Synthesis b. Porphobilinogen Synthesis c. Uroporphyrinogen Synthesis d. Decarboxylation of Uroporphyrinogen III e. Conversion of Protoporphyrinogen to Protoporphyrin 10) Rate limiting enzyme in heme synthesis a. Heme Synthase b. ALA Dehydratase c. Uroporphyrinogen synthase d. ALA Synthase 11) All of the Following are precursors of heme except a. Porphobilinogen b. Urobilinogen c. Uroporphyrinogen d. Protoporphyrinogen 12) HbA differs from HbF in that a. HbA has only alpha chains b. HbF cannot bind to 2,3 BPG c. HbF can bind only 2 molecules of Oxygen d. HbA contains γ-Chains