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11:22:11 - Review for Exam III (Part 2)

11:22:11 - Review for Exam III (Part 2) - Iron Fe 2 4 g of...

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Iron - Fe 2 – 4 g of iron present in the human body 39 mg/kg female 50 mg/kg male >65% hemoglobin - Iron-containing oxygen-transport metalloprotein in the red blood cells. 10% myoglobin an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals 1-5% part of enzymes Remainder found in blood or storage Distribution Amount is dependent on body weight, gender, age, pregnancy, growth state.
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Types: Heme iron – or “animal source” is found in the hemoglobin and myoglobin of animal products in the diet. (50 – 60% of animal tissue protein) Nonheme iron – or “plant source” bound to components of food. (plant and some animal source, milk) Digestion and Absorption Heme iron: hydrolyzed by proteases in stomach and small intestine. It must be released from the porphyrin ring •Heme carrier protein is present in the proximal small intestine. •Heme iron absorption takes place throughout the small intestine but is most efficient in the proximal duodenum. Iron can bind with ligands and chelating agents. If the bonds are strong and insoluble iron will not be absorbed.
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Fig. 12-2, p. 472 Digestion and Absorption Heme iron: hydrolyzed by proteases in stomach and small intestine. It must be released from the porphyrin ring Heme carrier protein is present in the proximal small intestine. Heme iron absorption takes place throughout the small intestine but is most efficient in the proximal duodenum. Iron can bind with ligands and chelating agents. If the bonds are strong and insoluble iron will not be absorbed. Structure
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Absorption enhanced by: acids - ascorbic, citric, lactic and tartaric acid mucin – acts as s chelate that aids iron absorption sugars (esp. fructose and sorbitol) meat, poultry and fish – cysteine and histidine Vitamin C - is especially helpful for iron absorption. These chemicals can act as chelating agents or ligands that bind with iron and enhance absorption Absorption inhibited by: polyphenols – coffee and tea oxalic acid – in chard berried, chocolate and tea phytates – in whole grains and cereals phosvitin – a protein found in egg yolks nutrients such as calcium, calcium phosphate salts, zinc, manganese, and nickel These chemical bind iron in the intestinal lumen and decrease iron absorption
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Regulation Hepcidin – protein secreted by the liver in response to adequate iron levels. causes ↓’d levels of ferroportin – stops iron absorption. HFE – promotes uptake of iron by transferrin Dcytb and DMT1 – promote iron absorption The body will store some iron in the intestinal cells as apoferritin . The intestinal cells will also use iron for a variety of purposes such as cofactor for enzymes. Transport Transfer across the basolateral membrane requires ferroportin.
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