W1-4 Iron, V B12, folic acid metabolism

Questions and Answers

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

Inhibiting iron absorption in the intestine

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

Small intestine

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

Red meat

In which type of anemia is iron overload commonly observed?

Anemia of chronic disease Signup and view all the answers

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

Supports red blood cell production Signup and view all the answers

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

Transferrin receptor downregulation Signup and view all the answers

Which form of iron is absorbed more efficiently?

Heme iron Signup and view all the answers

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

Liver Signup and view all the answers

Which molecule carries most of the iron in circulation?

Transferrin Signup and view all the answers

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

Hepcidin Signup and view all the answers

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

Hephaestin Signup and view all the answers

What inhibits the uptake of iron in the duodenum?

Phytates Signup and view all the answers

What is the normal range for transferrin saturation?

20-40% Signup and view all the answers

Where is excess dietary iron stored in enterocytes?

Ferritin Signup and view all the answers

What molecule is responsible for receptor-mediated transferrin endocytosis?

Transferrin Signup and view all the answers

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

Ferritin Signup and view all the answers

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

Iron overload Signup and view all the answers

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

Transferrin Signup and view all the answers

What is the normal hematocrit level in infants at birth?

50-60% Signup and view all the answers

Which form of anemia is characterized by bone marrow failure?

Aplastic anemia Signup and view all the answers

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

18 mg/day Signup and view all the answers

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

Thalassemia Signup and view all the answers

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

Hemochromatosis Signup and view all the answers

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

Reduced hepcidin secretion Signup and view all the answers

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

$\text{Transferrin Saturation}$ Signup and view all the answers

What does serum ferritin measure?

$\text{Tissue iron stores}$ Signup and view all the answers

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

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

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

Conjugates it Signup and view all the answers

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

Brown Signup and view all the answers

What happens to some urobilinogen before being excreted?

It is re-absorbed and oxidized in the kidney Signup and view all the answers

What is the primary role of folate in erythropoiesis?

Facilitation of heme synthesis Signup and view all the answers

Why does the absence of folate cause anemia?

Impairment of red blood cell maturation Signup and view all the answers

Which dietary sources are rich in folate?

Beans and spinach Signup and view all the answers

In which situations is folate deficiency likely to occur?

Vegetarian diet lacking leafy greens Signup and view all the answers

Why is folate deficiency a special concern during pregnancy?

It increases the risk of neural tube defects in the fetus Signup and view all the answers

How can folate antagonism be used pharmacologically?

To induce folate deficiency in cancer cells Signup and view all the answers

What are primary dietary sources of cobalamin (B12)?

Meat, fish, and dairy products Signup and view all the answers

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

Active transport by sodium-coupled carriers Signup and view all the answers

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

Homocysteine and methylmalonic acid Signup and view all the answers

What is the mechanism of B12 malabsorption?

Defective intrinsic factor production Signup and view all the answers

What is the primary form of iron in the body?

Hemoglobin Signup and view all the answers

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

UDP-glucuronosyltransferase Signup and view all the answers

What is the normal range for serum bilirubin levels?

2-17 micromolar Signup and view all the answers

What can cause prehepatic jaundice?

Hemolysis Signup and view all the answers

What are the dietary sources of folate?

Green leafy vegetables and liver Signup and view all the answers

Which condition can result from a deficiency in folate?

Megaloblastic anemia Signup and view all the answers

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

Methionine synthase Signup and view all the answers

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

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

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

Methylation of DNA/RNA Signup and view all the answers

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

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

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

$ ext{N5-formimino-THF}$ Signup and view all the answers

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

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

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

Ferritin Signup and view all the answers

Which enzyme activity facilitates iron storage in ferritin?

Ferroxidase Signup and view all the answers

What is the normal range for blood ferritin in men?

18-270 micrograms per liter Signup and view all the answers

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

Mitochondria themselves Signup and view all the answers

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

Hepcidin Signup and view all the answers

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

Apoferritin Signup and view all the answers

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

Ferric hydroxyphosphate FeO(OH) Signup and view all the answers

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

Lower both circulating iron and dietary absorption Signup and view all the answers

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

Light chains 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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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.

W1-4 Iron, V B12, folic acid metabolism

Questions and Answers

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

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

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

In which type of anemia is iron overload commonly observed?

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

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

Which form of iron is absorbed more efficiently?

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

Which molecule carries most of the iron in circulation?

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

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

What inhibits the uptake of iron in the duodenum?

What is the normal range for transferrin saturation?

Where is excess dietary iron stored in enterocytes?

What molecule is responsible for receptor-mediated transferrin endocytosis?

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

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

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

What is the normal hematocrit level in infants at birth?

Which form of anemia is characterized by bone marrow failure?

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

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

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

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

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

What does serum ferritin measure?

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

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

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

What happens to some urobilinogen before being excreted?

What is the primary role of folate in erythropoiesis?

Why does the absence of folate cause anemia?

Which dietary sources are rich in folate?

In which situations is folate deficiency likely to occur?

Why is folate deficiency a special concern during pregnancy?

How can folate antagonism be used pharmacologically?

What are primary dietary sources of cobalamin (B12)?

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

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

What is the mechanism of B12 malabsorption?

What is the primary form of iron in the body?

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

What is the normal range for serum bilirubin levels?

What can cause prehepatic jaundice?

What are the dietary sources of folate?

Which condition can result from a deficiency in folate?

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

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

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

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

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

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

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

Which enzyme activity facilitates iron storage in ferritin?

What is the normal range for blood ferritin in men?

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

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

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

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

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

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

Study Notes

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