Term
| What are some dietary sources of iron? |
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Definition
| liver, meat products, plant sources (esp leafy greens) |
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Term
| What are the 3 forms of iron in our diet? Which are organic, which are inorganic? |
|
Definition
Ferrous (Fe2+)
Ferric (Fe3+)
Heme
Heme is organic. Inorganic is a combination of ferric & ferrous iron |
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Term
| What is the bioavailability of heme iron? Ferric iron? Ferrous iron? |
|
Definition
Heme: 20%
Ferrous: poor availability
Ferric: terrible availability |
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Term
| What are the general biological functions of iron? |
|
Definition
1. Oxygen transport (hemoglobin, myoglobin)
2. Redox rxns (important in ETC!)
3. Iron metalloenzymes |
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Term
| How does non-heme dietary iron cross the apical brush border? |
|
Definition
1. HCl + proteases in stomach cleave iron from food components
2. Ferric iron is reduced to ferrous iron by reductase
3. Fe2+ is absorbed via divalent metal transporter 1 (DMT1) |
|
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Term
| What transporters are involved in bringing dietary iron across the brush border? |
|
Definition
DMT1 mediates Fe2+ import
HCP1 mediates heme iron import |
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Term
| How does heme dietary iron cross the apical brush border? |
|
Definition
1. HCL proteases in stomach release heme iron from hemoglobin/myoglobin
2. Heme porphyrin ring is absorbed via HCP1 transporter
3. Heme oxygenase hydrolyzes heme porphyrin ring, producing Fe2+ & protoporphyrin |
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|
Term
| What are chelators? What effect do they have on iron absorption? |
|
Definition
Small organic compounds that form a complex with a metal ion. They affect absorption of inorganic iron.
-soluble chelators enhance absorption e.g. amino acids, soluble fibres
-insoluble chelators decrease absorption
e.g. oxalate, phytate, insoluble fibers |
|
|
Term
| What effect does Vit C have on iron absorption? |
|
Definition
acts as a reducing agent & chelator with ferric iron, enhancing absorption of inorganic iron
Fe3+ -> Fe2+ |
|
|
Term
| What effect does Vit C have on heme iron absorption? |
|
Definition
| None, it only improves absorption of inorganic iron |
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Term
| What happens after inorganic & organic iron have crossed the brush border and are in the intestinal mucosal cell? |
|
Definition
1. Iron pools up in the intestinal musocal cell
2. Ceruloplasmin oxidizes Fe2+ to Fe3+ & binds it to transferrin
3. Transferrin-iron complex travels through the ferroportin transporter & circulates in the bloodstream |
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Term
| What form of iron can move in solution? |
|
Definition
|
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Term
| What form of iron can be bound to proteins for transport or storage? |
|
Definition
|
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Term
| How does iron move in the circulatory system? |
|
Definition
| bound to a protein called transferrin |
|
|
Term
| How does a cell obtain iron from the blood? |
|
Definition
1. Cell expresses a transferrin-iron complex receptor
2. Receptor binds to cell membrane & is internalized
3. Fe2+ is released & able to be used within the cell |
|
|
Term
| What are some cellular uses of iron? |
|
Definition
-cytochrome production
-iron:sulfur proteins
-iron metalloenzymes |
|
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Term
|
Definition
| enzymes which require a metal ion to act as a cofactor, enabling them to function |
|
|
Term
|
Definition
| A copper metalloenzyme which oxidizes ferrous iron to ferric iron & binds it to a tranferrin protein |
|
|
Term
| What transporter carries iron from the intestinal mucosal cell into the bloodstream? |
|
Definition
|
|
Term
| What is transferrin saturation? At what point is it reached? |
|
Definition
the point at which transferrin will not accept any more iron
-usually around 40% of actual saturation |
|
|
Term
| What happens when the transferrin saturation point is reached? |
|
Definition
-remaining iron in the intestinal mucosal cell is bound to ferritin, forming a storage complex
-intestinal mucosal cell will die & be excreted, taking the excess iron with it |
|
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Term
| What happens if there is an extreme excess of iron in the diet? |
|
Definition
1. Ferritin complexes will accumulate in the liver
2. Ferritin is oxidized into hemosiderin
3. Hemosiderin can cause liver failure |
|
|
Term
True or False
Hemosiderosis is more commonly observed in south african tribes due to traditional cooking practices for alcoholic beverages |
|
Definition
True!
However, generally iron toxicity is not commonly observed |
|
|
Term
| How could you treat an iron overload in the diet? |
|
Definition
| chelating drugs or blood letting |
|
|
Term
| How is iron excreted once absorbed? |
|
Definition
| We have no excretion mechanism once iron is absorbed, which is why excess iron can be toxic (although rare!) |
|
|
Term
| Why might a B6 deficiency lead to anemia? |
|
Definition
-iron molecules in cytochromes, myglobin & hemoglobin are in heme
-heme requires porphyrin synthesis
-porphyrin synthesis requires glycine & Vit B6 |
|
|
Term
| What is microcytic hypochromic anemia? |
|
Definition
a condition due to an iron & copper deficiency, characterized by many small, pale RBC's
(ceruloplasmin is dysfunctional) |
|
|
Term
True or False
Poor work performance resulting from an iron deficiency is mainly due to reduced oxygen carrying capacity in the blood |
|
Definition
False
It is mainly due to iron functions within the tissues |
|
|
Term
True or False
Mild, permanent mental retardation & impaired neural function are a risk of an Fe deficiency |
|
Definition
|
|
Term
| What hormone regulates iron metabolism? How? |
|
Definition
Hepcidin
-binds to ferroportin when TS is reached, preventing more iron from being absorbed into the bloodstream |
|
|
Term
|
Definition
| formation of blood cellular components, requires iron |
|
|
Term
| What are some dietary sources of copper? |
|
Definition
oysters & shellfish
whole grains
beans, nuts, potatoes, dark leafy greens
organ meats |
|
|
Term
| What enzymatic processes is copper a part of? |
|
Definition
1. Iron metabolism (ceruloplasmin)
2. Energy production (cyt. c oxidase)
3. Antioxidant (superoxide dismutase)
4. Norepinephrine production
5. Melanin formation (tyrosine is dependent on Cu)
6. Elastin structure (lysyl oxidase)
Cu acts as an enzyme cofactor & is often a intermediate in redox reactions |
|
|
Term
| What transporters carry copper into intestinal mucosal cells, from the lumen of the SI? |
|
Definition
Copper Trans I (CTR1)
Divalent Metal Transporter 1 (DMT1) |
|
|
Term
| What might affect absorption of dietary Cu? |
|
Definition
soluble ligands (AA's & vit C) increase absorption
insoluble ligands decrease absorption |
|
|
Term
| How does phytate affect the absorption of copper & iron? |
|
Definition
| Forms insoluble complexes which decrease absorption |
|
|
Term
| What happens if there is a high percentage of dietary Cu present in intestinal cells? |
|
Definition
-production of the protein metallothionein is induced
-metallothionein traps copper, it will be excreted in the feces when the intestinal cells slough off |
|
|
Term
| Aside from copper, what else might induce metaliothionein? What effect does his have? |
|
Definition
High dietary zinc can also induce this protein
-MT has a higher affinity for copper than zinc though, so this can cause a copper defficiency |
|
|
Term
|
Definition
|
|
Term
| How is copper transported from the liver to various tissues? |
|
Definition
|
|
Term
| What is the relationship between low ceruloplasmin & copper? |
|
Definition
| microcytic hypochromic anemia may occur (secondary iron deficiency), and copper will not be able to be transported to the necessary tissues |
|
|
Term
| What are the symptoms/effects of a copper deficiency? |
|
Definition
-microcytic hypochromic anemia
-depigmentation of skin & hair
-less CuZn superoxid dismutase (SOD) activity = oxidant stress
-reduced lysyl oxidase activity (a copper enzyme) = poor elastin formation, weakened arteries, risk of aortic rupture |
|
|
Term
| In what state is zinc typically found in organs, tissues & body fluids? |
|
Definition
|
|
Term
| What are some dietary sources of zinc? |
|
Definition
-oysters
-red meat & poultry
-beans, nuts, whole grains |
|
|
Term
| What metabolic functions is zinc associated with? |
|
Definition
-zinc metalloenzymes involved in all metabolic pathways
-oxygen radical metabolism (Cu/Zn superoxide dismutase)
-zinc fingers (DNA binding) |
|
|
Term
True or False
Zinc & copper participate at the reaction 'active' site of metalloenzymes |
|
Definition
|
|
Term
| How is zinc absorbed in the body? |
|
Definition
1. freed from protein binding by acids in the stomach & small intestine
2. absorbed via ZIP4 & DMT1 transporters |
|
|
Term
| What effect do elevated Zn levels have on Zn absorption? |
|
Definition
-induces metallotionein accumulation & degradation of ZIP4 transporter
-absorption decreases |
|
|
Term
| What transporters are involved with zinc absorption? |
|
Definition
|
|
Term
| What chelators enhance/inhibit Zn absorption? |
|
Definition
Enhance: some AA's, organic acids e.g. citrate
Inhibit: phytic acid, oxalic acid |
|
|
Term
True or False
A zinc deficiency is not likely to cause many biological problems |
|
Definition
False
Zinc is involved in over 200 enzymatic activities, a deficiency is problematic! |
|
|
Term
| What is the fate of zinc after it has entered intestinal mucosal cells? |
|
Definition
-used functionally
-bound to metallothionine, stored & excreted
-secreted into circulation, bound to albumin |
|
|
Term
| What is the 1st destination of zinc if it enters the circulatory system? |
|
Definition
|
|
Term
| What protein does zinc bind to in order to circulate throughout the body? |
|
Definition
|
|
Term
| What are some symptoms/effects of a zinc deficiency? |
|
Definition
-reduced growth in children
-impaired sexual development in males
-malformation of DNA binding proteins & 'zinc fingers'
-inadequate cell division
-poor wound healing
-insufficient taste proteins |
|
|
Term
| What are the effects of an excess of zinc in the diet? |
|
Definition
-induction of metallothionine leads to a copper deficiency
-neurological issues
-numbness
-metallic taste
-nausea |
|
|
Term
True or False
Zinc is an important component in regulating gene expression |
|
Definition
True
It is found in transcription factors & alters DNA binding of amino acids |
|
|
Term
| What is the importance of magnesium in relation to ATP? |
|
Definition
| all metabolically active ATP is bound to magnesium |
|
|
Term
True or False
Excess calcium intake might impair function of magnesium |
|
Definition
|
|
Term
| What are some symptoms/effects of a Mg deficiency? |
|
Definition
-Type 2 diabetes
-hypertension
-osteoporosis
-colon cancer
-cardiovascular issues
-seizures
-muscle weakness & tremors
-cardiac arrhythmias |
|
|
Term
| Where is manganese primarily found in the body? |
|
Definition
|
|
Term
| What is the importance of manganese in the urea cycle? |
|
Definition
| it is a component of the enzyme arginase, the last step of the urea cycle |
|
|
Term
| What is the metabolic relationship between Mn & biotin? |
|
Definition
| Mn & biotin cooperate in gluconeogenesis & fatty acid synthesis |
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