W1-4 Iron, V B12, folic acid metabolism
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Questions and Answers

Which of the following is a function of hepcidin in the regulation of iron absorption?

  • Inhibiting iron absorption in the intestine (correct)
  • Activating iron storage in tissues
  • Promoting iron absorption in the intestine
  • Supporting iron transport in the blood

    • What is the main site of absorption for iron in the human body?

  • Stomach
  • Large intestine
  • Small intestine (correct)
  • Colon

    • Which of the following is a common dietary source of iron?

  • Red meat (correct)
  • Leafy green vegetables
  • Fish oil
  • Citrus fruits

    • In which type of anemia is iron overload commonly observed?

    <p>Anemia of chronic disease</p> Signup and view all the answers

    What is the role of folate in red blood cell production?

    <p>Supports red blood cell production</p> Signup and view all the answers

    Which mechanism is responsible for the regulation of iron acquisition by cells from the blood?

    <p>Transferrin receptor downregulation</p> Signup and view all the answers

    Which form of iron is absorbed more efficiently?

    <p>Heme iron</p> Signup and view all the answers

    Where is most of the iron in the body tightly bound to proteins?

    <p>Liver</p> Signup and view all the answers

    Which molecule carries most of the iron in circulation?

    <p>Transferrin</p> Signup and view all the answers

    What is the major regulatory hormone for iron absorption and use?

    <p>Hepcidin</p> Signup and view all the answers

    Which molecule is responsible for converting Fe3+ to Fe2+ for transport through the divalent metal transporter?

    <p>Hephaestin</p> Signup and view all the answers

    What inhibits the uptake of iron in the duodenum?

    <p>Phytates</p> Signup and view all the answers

    What is the normal range for transferrin saturation?

    <p>20-40%</p> Signup and view all the answers

    Where is excess dietary iron stored in enterocytes?

    <p>Ferritin</p> Signup and view all the answers

    What molecule is responsible for receptor-mediated transferrin endocytosis?

    <p>Transferrin</p> Signup and view all the answers

    Where can re-oxidized Iron be stored as Fe3+?

    <p>Ferritin</p> Signup and view all the answers

    What can lead to inhibition of iron uptake in the duodenum?

    <p>Iron overload</p> Signup and view all the answers

    What molecule binds Fe3+ in the blood during iron circulation?

    <p>Transferrin</p> Signup and view all the answers

    What is the normal hematocrit level in infants at birth?

    <p>50-60%</p> Signup and view all the answers

    Which form of anemia is characterized by bone marrow failure?

    <p>Aplastic anemia</p> Signup and view all the answers

    What is the daily iron allowance in the US for menstruating women?

    <p>18 mg/day</p> Signup and view all the answers

    Which condition is caused by the inability to make hemoglobin α or β chains?

    <p>Thalassemia</p> Signup and view all the answers

    What is the common genetic form of iron overload in Europeans?

    <p>Hemochromatosis</p> Signup and view all the answers

    What does homozygosity for the C282Y mutation in the HFE gene lead to?

    <p>Reduced hepcidin secretion</p> Signup and view all the answers

    Which measurement is a good indicator of iron deficiency or overload?

    <p>$\text{Transferrin Saturation}$</p> Signup and view all the answers

    What does serum ferritin measure?

    <p>$\text{Tissue iron stores}$</p> Signup and view all the answers

    Why is serum ferritin a good indicator of iron stores and excess iron?

    <p>$\text{It comes from sloughed off cells which release ferritin}$</p> Signup and view all the answers

    What does the liver do to bilirubin before excreting it into the bile and intestine?

    <p>Conjugates it</p> Signup and view all the answers

    What color is urobilinogen mostly converted into by bacteria and excreted?

    <p>Brown</p> Signup and view all the answers

    What happens to some urobilinogen before being excreted?

    <p>It is re-absorbed and oxidized in the kidney</p> Signup and view all the answers

    What is the primary role of folate in erythropoiesis?

    <p>Facilitation of heme synthesis</p> Signup and view all the answers

    Why does the absence of folate cause anemia?

    <p>Impairment of red blood cell maturation</p> Signup and view all the answers

    Which dietary sources are rich in folate?

    <p>Beans and spinach</p> Signup and view all the answers

    In which situations is folate deficiency likely to occur?

    <p>Vegetarian diet lacking leafy greens</p> Signup and view all the answers

    Why is folate deficiency a special concern during pregnancy?

    <p>It increases the risk of neural tube defects in the fetus</p> Signup and view all the answers

    How can folate antagonism be used pharmacologically?

    <p>To induce folate deficiency in cancer cells</p> Signup and view all the answers

    What are primary dietary sources of cobalamin (B12)?

    <p>Meat, fish, and dairy products</p> Signup and view all the answers

    How is cobalamin (B12) primarily absorbed in the intestines?

    <p>Active transport by sodium-coupled carriers</p> Signup and view all the answers

    What metabolites are elevated in the blood in deficiencies of both folate and B12?

    <p>Homocysteine and methylmalonic acid</p> Signup and view all the answers

    What is the mechanism of B12 malabsorption?

    <p>Defective intrinsic factor production</p> Signup and view all the answers

    What is the primary form of iron in the body?

    <p>Hemoglobin</p> Signup and view all the answers

    Which enzyme is responsible for the conversion of heme to bilirubin diglucuronide?

    <p>UDP-glucuronosyltransferase</p> Signup and view all the answers

    What is the normal range for serum bilirubin levels?

    <p>2-17 micromolar</p> Signup and view all the answers

    What can cause prehepatic jaundice?

    <p>Hemolysis</p> Signup and view all the answers

    What are the dietary sources of folate?

    <p>Green leafy vegetables and liver</p> Signup and view all the answers

    Which condition can result from a deficiency in folate?

    <p>Megaloblastic anemia</p> Signup and view all the answers

    Which enzyme uses B12 as a cofactor in the synthesis of methionine?

    <p>Methionine synthase</p> Signup and view all the answers

    What is the role of 5-methyl-THF in the folate trap hypothesis?

    <p>It traps folate as 5-methyl-folate, leading to insufficiency</p> Signup and view all the answers

    What is the primary role of folate in single carbon metabolism?

    <p>Methylation of DNA/RNA</p> Signup and view all the answers

    Which structure acts as a single methyl group donor in folate biochemistry?

    <p>$ ext{N}^5 ext{-Methyl-THF}$</p> Signup and view all the answers

    What is the degradation product of histidine that leads to Formimino-THF?

    <p>$ ext{N5-formimino-THF}$</p> Signup and view all the answers

    What is the irreversible reaction catalyzed by MTHFR in folate biochemistry?

    <p>Conversion of $ ext{5,10-N-methylene-THF}$ to $ ext{5-Methyl-THF}$</p> Signup and view all the answers

    Where is iron stored in cells as the major storage form?

    <p>Ferritin</p> Signup and view all the answers

    Which enzyme activity facilitates iron storage in ferritin?

    <p>Ferroxidase</p> Signup and view all the answers

    What is the normal range for blood ferritin in men?

    <p>18-270 micrograms per liter</p> Signup and view all the answers

    In which cellular organelle does the translocation of iron to mitochondria occur?

    <p>Mitochondria themselves</p> Signup and view all the answers

    What is the name of the liver hormone that acts to lower circulating iron levels?

    <p>Hepcidin</p> Signup and view all the answers

    Which protein protects mRNA from degradation in the presence of iron deficiency?

    <p>Apoferritin</p> Signup and view all the answers

    What is the mineral form in which iron is stored within ferritin?

    <p>Ferric hydroxyphosphate FeO(OH)</p> Signup and view all the answers

    What is the net effect of increased hepcidin levels on circulating iron and dietary absorption?

    <p>Lower both circulating iron and dietary absorption</p> Signup and view all the answers

    Which type of chains in the ferritin complex lack enzymatic ferroxidase activity but facilitate iron storage?

    <p>Light chains</p> Signup and view all the answers

    Study Notes

    • Dr. Zahi Damuni, Ph.D. can be contacted at [email protected] for queries or to schedule a one-on-one meeting.
    • He teaches about iron, vitamin B12, and folate metabolism using the Lippincott Illustrated Reviews in Biochemistry, specifically Chapters 28 (folate and vitamin B12), 29 (section III.B on Iron), and 21 (section on Heme degradation).
    • The focus of the lectures includes anemia and erythropoiesis, iron metabolism, heme regulation and jaundice, iron storage, and folate and B12 metabolism.
    • Erythropoiesis requires iron, folate, and vitamin B12 for proliferation of cells, heme synthesis, and DNA synthesis.
    • Anemia can have various causes including blood loss, decreased erythrocyte production, hemolysis, and nutrient deficiencies.
    • Iron-deficiency anemia results in microcytic and hypochromic erythrocytes, and symptoms include fatigue, weakness, pallor, chest pain, and pale skin among others.
    • Iron has two important properties: as an electron carrier in redox reactions and as a reversible oxygen binding agent.
    • Iron is present in many proteins, including hemoglobin, myoglobin, and cytochromes, and plays a key role in electron transfer and oxidation-reduction processes.
    • Iron from dietary sources includes heme iron (from meat) and non-heme iron (from vegetables), and the recommended intake is 8-18 mg daily.
    • Absorption of iron is regulated to prevent the toxic effects of free iron, with heme iron being absorbed more efficiently than non-heme iron.
    • Iron is stored in the liver, bone marrow, and reticuloendothelial macrophages, and circulates in the blood bound to transferrin.
    • The major stores of iron are in the liver (around 1g), reticuloendothelial macrophages (around 0.6g), erythrocytes (around 1.8g), and bone marrow (around 0.3g).

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    Iron, B12, Folic Acid Metabolism PDF

    Description

    Test your knowledge on the translocation and storage of iron in cells, including its incorporation into heme and iron-sulfur clusters, as well as its storage in ferritin. Understand the regulatory mechanisms and clinical significance of iron storage in cells.

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