L3 QS, BMS201.pdf

MCQs on Heme Structure & Synthesis 1. Which of the following best describes the shape of a red blood cell (RBC)? a) Spherical b) Biconcave disc c) Concave disc d) Irregular 2. What is the average lifespan of a red blood cell in peripheral circulation? a) 60 days b) 90 days c...

MCQs on Heme Structure & Synthesis 1. Which of the following best describes the shape of a red blood cell (RBC)? a) Spherical b) Biconcave disc c) Concave disc d) Irregular 2. What is the average lifespan of a red blood cell in peripheral circulation? a) 60 days b) 90 days c) 120 days d) 150 days 3. Where does the synthesis of red blood cells primarily occur? a) Liver b) Spleen c) Bone marrow d) Lymph nodes 4. Which of the following organelles are absent in mature red blood cells? a) Nucleus b) Mitochondria c) Both a and b d) None of the above 5. What is the primary function of mature red blood cells? a) Transport oxygen and carbon dioxide b) Fight infections c) Produce antibodies d) Clot blood 6. Hemoglobin is classified as which type of protein? a) Simple protein b) Conjugated protein c) Derived protein d) Fibrous protein 7. What are the components of a conjugated protein like hemoglobin? a) Heme and Globin b) Amino acids only  c) Carbohydrates and lipids d) Nucleic acids and proteins 8. What is the normal concentration of hemoglobin in adult males? a) 10.5 - 13.5 gm/dl b) 12.0 - 14.8 gm/dl c) 13.5 - 16.5 gm/dl d) 15.0 - 18.0 gm/dl 9. Which type of hemoglobin constitutes the majority of adult hemoglobin? a) HbA b) HbA2 c) HbF d) HbA1c 10. How many heme groups and globin chains are present in one molecule of adult hemoglobin (HbA)? a) 2 heme groups and 2 globin chains b) 2 heme groups and 4 globin chains c) 4 heme groups and 2 globin chains d) 4 heme groups and 4 globin chains 11. What types of globin chains are found in adult hemoglobin (HbA)? a) 2 alpha and 2 beta chains b) 2 alpha and 2 gamma chains c) 4 alpha chains d) 4 beta chains 12. How many amino acids are present in an alpha chain of globin? a) 141 b) 146 c) 151 d) 156 13. Which of the following best describes the structure of heme? a) Iron porphyrin b) Magnesium porphyrin c) Copper porphyrin d) Zinc porphyrin 14. What is a porphyrin composed of? a) Four pyrrole rings linked by methenyl bridges  b) Four pyrrole rings linked by ethylene bridges c) Three pyrrole rings linked by methenyl bridges d) Three pyrrole rings linked by ethylene bridges 15. In heme, iron forms complexes with which atoms of the porphyrin? a) Carbon atoms b) Nitrogen atoms c) Oxygen atoms d) Sulfur atoms 16. Which of the following is NOT a hemoprotein? a) Hemoglobin b) Myoglobin c) Cytochrome P450 d) Insulin 17. Where does the majority of heme synthesis occur in the body? a) Bone marrow and liver b) Spleen and pancreas c) Kidneys and lungs d) Brain and heart 18. In which cellular organelle do the first and last three reactions of heme synthesis take place? a) Mitochondria b) Cytosol c) Nucleus d) Endoplasmic reticulum 19. Where do the intermediate steps of heme synthesis occur? a) Mitochondria b) Cytosol c) Nucleus d) Endoplasmic reticulum 20. Which of the following are the starting materials for the synthesis of ALA (aminolevulinic acid)? a) Succinyl CoA and Alanine b) Succinyl CoA and Glycine c) Acetyl CoA and Alanine d) Acetyl CoA and Glycine 21. Which enzyme catalyzes the first step of heme synthesis (synthesis of ALA)? a) ALA dehydratase b) ALA synthase c) Ferrochelatase d) Porphobilinogen deaminase 22. The first step of heme synthesis is considered the key regulatory step. Which of the following inhibits ALA synthase 1 in the liver? a) Heme b) Iron c) Hypoxia d) Erythropoietin 23. In the last step of heme synthesis, iron is attached to protoporphyrin IX. What is the oxidation state of iron in this step? a) Fe+3 (ferric form) b) Fe+2 (ferrous form) c) Fe+1 d) Fe0 24. Which enzyme catalyzes the last step of heme synthesis? a) ALA dehydratase b) ALA synthase c) Ferrochelatase d) Porphobilinogen deaminase 25. Lead poisoning inhibits two enzymes in the heme synthesis pathway. Which of the following is NOT one of them? a) Ferrochelatase b) ALA dehydratase c) ALA synthase d) Protoporphyrinogen oxidase 26. Which of the following accumulates in the blood and urine due to lead poisoning's inhibition of ferrochelatase? a) ALA b) Porphobilinogen c) Protoporphyrin IX d) Uroporphyrinogen 27. In the liver, ALA synthase 1 is inhibited by all of the following EXCEPT:  a) Heme b) Hemin c) Glucose d) Iron 28. In erythroblasts, ALA synthase 2 is primarily regulated by: a) Heme b) Hemin c) Glucose d) Iron availability 29. What is the definition of porphyria? a) Decreased blood porphyrins and their excretion in urine b) Increased blood porphyrins above the normal level and their excretion in urine c) Normal blood porphyrin levels with no excretion in urine d) Absence of porphyrins in the blood and urine 30. What is the underlying cause of porphyrias? a) Deficiency of one of the enzymes in the heme synthesis pathway b) Excess of one of the enzymes in the heme synthesis pathway c) Normal functioning of all enzymes in the heme synthesis pathway d) None of the above 31. Which of the following is NOT a classification of porphyria? a) Erythropoietic porphyria b) Hepatic porphyria c) Renal porphyria d) Acquired porphyria 32. Which type of porphyria is associated with photosensitivity and skin rash? a) Erythropoietic porphyria b) Hepatic porphyria c) Renal porphyria d) Acquired porphyria 33. Which type of porphyria is associated with abdominal pain and neuropsychiatric symptoms? a) Erythropoietic porphyria b) Hepatic porphyria c) Renal porphyria d) Acquired porphyria 34. Which of the following is an acquired porphyria? a) Lead poisoning b) Erythropoietic porphyria c) Acute intermittent porphyria d) None of the above 35. Which of the following is NOT a manifestation of porphyria? a) Darkening of urine b) Photosensitivity c) Peripheral neuropathy d) Hypotension 36. During an acute attack of porphyria, which metabolite is typically elevated in urine? a) ALA b) Porphobilinogen c) Protoporphyrin IX d) Uroporphyrinogen 37. Which of the following is used in the diagnosis of porphyrias? a) Measurement of porphobilinogen in urine b) Measurement of heme synthesis metabolites in plasma, urine, feces, and erythrocytes c) Identification of the defective enzyme d) All of the above 38. Heme synthesis occurs entirely in the mitochondria. (True/False) 39. ALA is synthesized from succinyl CoA and alanine. (True/False) 40. Hemin and glucose increase the activity of ALA1 synthesis. (True/False) Answer Key: 1. b) 2. c) 3. c) 4. c) 5. a) 6. b) 7. a) 8. c) 9. a) 10. d) 11. a) 12. a) 13. a) 14. a) 15. b) 16. d) 17. a) 18. a) 19. b) 20. b) 21. b) 22. a) 23. b) 24. c) 25. d) 26. c) 27. d) 28. d) 29. b) 30. a)  31. c) 32. a) 33. b) 34. a) 35. d) 36. b) 37. d) 38. False 39. False 40. False Done