Nutritional Anemias: Iron

Vocabulary practice flashcards covering macro and micro elements, iron sources, absorption mechanisms, transporters, regulation, storage, function, recommendations, and toxicity based on the Nutritional Anemias lecture.

Macroelements

Essential mineral elements required by the body at rates greater than $100\,mg/d$, including calcium, phosphorous, magnesium, sodium, potassium, and chloride.

Trace Elements

Microelements required by the body at rates between $1\,mg/d$ and $100\,mg/d$, including iron, zinc, copper, manganese, and fluorine.

Ultratrace Elements

Microelements required by the body at rates less than $1\,mg/d$, including selenium, molybdenum, iodine, chromium, boron, and cobalt.

Heme Iron

An organic form of iron consisting of iron bound to a protoporphyrin ring, derived from animal foods (liver, beef, clams, oysters, dark meat poultry) and absorbed at a rate of $15\text{--}35\%$.

Nonheme Iron

An inorganic form of iron found in plant foods (nuts, legumes, green leafy vegetables, dried fruit, tofu), dairy, fortified grains, and oral supplements, absorbed at a rate of $2\text{--}20\%$.

Heme Carrier Protein 1 (hcp 1)

A transporter located primarily in the proximal small intestine that absorbs intact heme iron across the brush border membrane.

Divalent Metal Transporter 1 (DMT1)

Also known as DCT1, the primary cation transporter that moves ferrous iron ($Fe^{2+}$) across the brush border membrane into the enterocyte cytosol.

Enhancers of Non-Heme Iron Absorption

Dietary components that increase non-heme iron absorption, including sugars (fructose, sorbitol), acids (ascorbic, citric, lactic, tartaric), meat/poultry/fish (MFP) factors, and mucin.

Inhibitors of Non-Heme Iron Absorption

Dietary components that decrease non-heme iron absorption, including polyphenols (tannins in tea/coffee), oxalic acid, phytates, phosvitin in egg yolks, and other minerals (calcium, zinc, manganese, nickel).

Hepcidin

A liver-synthesized regulatory peptide controlled by systemic iron, erythropoiesis, and inflammation; it binds ferroportin when iron stores increase to prevent iron export out of cells.

Ferroportin

A transport protein that carries iron across the enterocyte's basolateral membrane into circulation, coupled with iron oxidation to $Fe^{3+}$ by hephaestin.

Hephaestin

A copper-containing protein that oxidizes ferrous iron ($Fe^{2+}$) to ferric iron ($Fe^{3+}$) during transport across the basolateral membrane via ferroportin.

Transferrin

A liver-synthesized $\beta$-globulin transport protein with two binding sites that transports up to 2 atoms of ferric iron ($Fe^{3+}$) in the blood (normally ~$30\%$ saturated).

Ferritin

The main cellular storage protein for iron, accounting for ~$\frac{2}{3}$ of stored iron, which is unstable and constantly degraded and resynthesized.

Hemosiderin

An insoluble breakdown product of denatured ferritin that increases during iron overload and is poorly available to supply iron when needed.

Hemoglobin

An erythrocyte protein composed of 4 protein chains each bound to a heme group with central ferrous iron ($Fe^{2+}$), containing approximately $70\%$ of total body iron.

Hemochromatosis

A genetic disorder causing chronic iron overload because the body cannot accurately sense iron stores and down-regulate intestinal absorption, leading to iron deposition and organ failure.

Sickle Cell Anemia

A structural hemoglobinopathy caused by a point mutation in the $\beta$-globin gene ($GAG \rightarrow GTG$, substituting glutamic acid with valine), causing the globin chain to precipitate into tactoids.

Recommended Dietary Allowance (RDA) for Iron

Daily intake recommendations for iron: $8\,mg$ for adult men, $18\,mg$ for premenopausal women, $8\,mg$ for postmenopausal women, $27\,mg$ during pregnancy, and $9\,mg$ during lactation.

Tolerable Upper Intake Level (UL) for Iron

The maximum safe daily intake limit for iron, set at $45\,mg/d$ to avoid acute toxicity and accidental iron overload.

Heme Structure

A porphyrin ring structure with a central ferrous iron ($Fe^{2+}$) atom.

Iron Absorption and Metabolism Diagram

Schematic representation showing the dual pathways of non-heme iron (reduced via Dcytb, imported via DMT1) and heme iron (imported via Hcp1/PCFT) absorption, cellular storage in ferritin, and export into capillary blood via ferroportin (Fp1) and transferrin (Tf).

Internal Iron Exchange

Diagram depicting the internal exchange of ferric iron ($Fe^{3+}$) and ferrous iron ($Fe^{2+}$) between plasma transferrin, red blood cell hemoglobin, tissue enzymes, ferritin, hemosiderin, and reticuloendothelial cells.