Iron Absorption, Transport, Metabolism and Regulation - Biochemistry Lesson

Summary

This biochemistry lesson explains the complex process of iron absorption, transport, and metabolism in the body. It begins with the ingestion of iron in the intestine, where it is reduced from Fe³⁺ to Fe²⁺ and absorbed into enterocytes. The absorbed iron is either stored or transported through the bloodstream by transferrin. The liver regulates iron levels by producing hepcidin, which controls iron absorption. The video also outlines the recommended daily intake of iron based on age, sex, and special conditions like pregnancy. This process ensures that the body maintains a healthy balance of iron, preventing both deficiency and overload.

Takeaways

• 😀 Iron is absorbed in the intestines, starting as Fe3+ (iron 3+), which is reduced to Fe2+ (iron 2+) by the protein duodenal cytochrome B.
• 😀 Fe2+ is transported into enterocytes (intestinal cells) via a transporter called divalent metal transporter 1 (DMT1).
• 😀 Once inside enterocytes, iron can either be bound to proteins like ferritin or remain free in the cell.
• 😀 Free Fe2+ is transported across the enterocyte membrane to the bloodstream via Ferroportin 1.
• 😀 The bones produce transferrin, which binds Fe2+ and transports it through the blood to various tissues.
• 😀 The liver regulates iron levels by sensing high transferrin and iron, releasing hepcidin to inhibit Ferroportin 1 and reduce iron absorption.
• 😀 Hepcidin prevents excess iron from entering the bloodstream by inhibiting Ferroportin 1 in enterocytes.
• 😀 When Ferroportin 1 is inhibited, iron stays in the enterocyte and is eventually excreted when the enterocyte is sloughed off and replaced every 3 days.
• 😀 Dietary iron can be found in two forms: heme iron (from animal sources) and non-heme iron (from plant-based foods).
• 😀 The recommended daily intake of iron varies by age and gender, with higher needs for females during menstruation and for pregnant women due to increased blood volume.

Q & A

What is the initial form of iron in the diet that enters the intestinal lumen?

The initial form of iron in the diet is Fe3+ (iron 3+), which enters the intestinal lumen after ingestion.

What is the role of duodenal cytochrome B in iron absorption?

Duodenal cytochrome B is a protein on the luminal side of enterocytes that reduces Fe3+ (iron 3+) to Fe2+ (iron 2+) in the intestinal lumen, making it more absorbable.

How does iron enter enterocytes from the lumen of the intestine?

Iron enters enterocytes through a transporter known as the divalent metal transporter 1 (DMT1), which facilitates the uptake of Fe2+ into the enterocyte.

What happens to iron once it enters an enterocyte?

Once inside the enterocyte, iron can either bind to storage proteins like ferritin or be transported to the bloodstream. If free, it is transported across the basolateral membrane into the blood.

What is the function of ferroportin in iron absorption?

Ferroportin is a transporter located on the basolateral side of enterocytes. It facilitates the transport of Fe2+ from the enterocyte into the bloodstream.

What role does transferrin play in iron metabolism?

Transferrin is a protein produced by the liver that binds to Fe2+ in the bloodstream, transporting it to various tissues, including the bone marrow for red blood cell production.

How does the body regulate iron absorption when iron levels are high?

When iron levels are high, hepatocytes release a hormone called hepcidin, which inhibits ferroportin, reducing iron transport into the bloodstream and preventing excess iron absorption.

What happens to iron in enterocytes if ferroportin is inhibited?

If ferroportin is inhibited, iron remains in the enterocyte and is eventually lost when the enterocyte is sloughed off and excreted in feces. Enterocytes are replaced every 3 days.

What dietary sources contain heme iron and non-heme iron?

Heme iron is found in animal-based foods, such as blood and meat, while non-heme iron is primarily found in plant-based foods.

How much iron should individuals of different age groups consume daily?

The recommended daily intake of iron varies by age and gender. For example, children aged 1-3 need 7 mg/day, adult males need 8 mg/day, females aged 19-50 need 18 mg/day due to menstruation, and pregnant women require about 27 mg/day.