LMP301 Lecture 13: Iron & Hemoglobin Flashcards
iron metabolism & hemoglobins
Majority of iron comes from…
diet
dietary iron is in the form…
ferric
Fe3+
Ferric iron is insoluble…
in basic conditions
5 - 10% of iron is absorbed at…
the duodenum
What happens to iron in the stomach?
- converted to Fe2+
- Fe2+ can be soluble in the basic duodenum, and thus absorbed
what increases iron absorption?
- ascorbic acid
- sugars
- AA
What decreases iron absorption?
- eggs
- cheese
- milk
- veggies
- tea
desquamation
the shedding of epithelial cells
Iron is lost through…
- desquamation
- menstrual flow
- urine
Iron is stored in…
- RBC (70%)
- Ferritin (20%)
- Myoglobin (5%)
Ferritin
intracellular protein that stores iron
__ is the transport protein for iron in the plasma
transferrin
Process of iron uptake into cells
- transferrin receptor binds transferrin holding iron
- endosome engulfs
- endosome pH changes to acidic
- iron is released from transferrin, and is pumped out of endosome
- (apo)transferrin-receptor is recycled
(apo)transferrin
transferrin without iron bound to it
transferrin has ____ binding sites for ___
2
Fe+++
Occupancy of transferrin sites
not always occupied
- only 25-50% of transferrin is normally saturated
What used to be an indirect way to measure transferrin concentration?
total iron binding capacity (TIBC)
Iron is an ____ element
essential
free iron is…
toxic
Iron is found complexed with…
- hemoglobin
- myoglobin
- cytochromes
binding of iron to proteins occurs though…
heme
Heme
- inorganic molecule
- Fe goes in the middle of the ring
Iron is stored as…
- ferritin
- hemosiderin
Ferritin can bind up to…
4500 iron atoms
This protects cells from free iron damage
Hemosiderin
= insoluble ferritin
- release iron slowly
1/3 of iron stores are in…
- liver
- spleen
- bone marrow
Iron diseases
- iron deficiency (anemia)
- iron overload
- iron poisoning
- chronic disease
Iron deficiency is common in…
women, children, elderly
Iron deficiency is usually associated with ___ because…
anemia
Iron stores are used up, so can’t make enough RBC
causes of iron deficiency
- loss of blood
- inadequate intake
What will happen to total iron binding capacity (TIBC) when iron decreases?
Increases
- there are more free sites, so the capacity increases
What is a good indicator of iron deficiency?
decreased serum ferritin
biochemical test: iron deficiency
- low serum iron
- high TIBC
- low iron saturation (< 25%)
- high serum transferrin
- low serum ferritin
- less Hb
- Hb smaller
- Hb lighter in colour
Iron saturation
ratio of ferritin:transferrin
hypochromic Hb
less iron in Hb, so colour is light pink instead of red
microcytic anemia
RBC becomes smaller than normal
symptoms of iron deficiency
- weakness / fatigue
- short breath
- incr. CO
- pale hair & nails
- disturbed behaviour in children
- impaired neurological development in infants
Treatment of iron deficiency
- mild: oral supplements (take wit vit C to increase absorption)
- anemia / chronic: erythropoietin
- severe anemia: blood transfusion
biochemical results of iron overload
- high serum iron
- high serum ferritin
- low TIBC
- high iron saturation (>50%)
Some causes of iron overload
- increased intake
- blood transfusions
- hereditary hemochromatosis
AR
hereditary hemochromatosis
10% of ____ carry the gene for hereditary hemochromatosis
northern Europeans
Occurance of the disease (homo/hetero)
not all homozygous people have the disease, meaning there are factors other than genetics
is hereditary hemochromatosis more common in men or women?
men
why are women protected from iron overload?
periods
symptoms of hereditary hemochromatosis is apparent by…because…
40 years old because the iron toxicity would have had enough time to do damage to some organs
gene responsible for hereditary hemochromatosis
HFE
Mutations lead to increased absorption & storage of iron
symptoms of hereditary hemochromatosis
- fatigue
- joint pain
- mood swings / depression
- bronze skin colour (liver can’t remove pigment)
- type II diabetes (pancreas harmed by iron)
- liver-heart-thyroid dysfunction
Iron overload will affect…
- liver
- pancreas
diagnosis of hereditary hemochromatosis
- high iron
- genetic testing for HFE gene
Treatment for iron overload
- venesection
- screen at risk relatives
Iron poisoning is…
acute disorder; extreme iron overload in the body
Iron poisoning is common in…
children
symptoms of iron poisoning
- nausea
- vomiting
- abdominal pain
- hematemesis (vomit blood)
treatment of iron poisoning
chelation with desferrioxamine
Why is venesection not used in iron poisoning treatment?
don’t want to remove that much blood from children
synthesis of Hb is stimulated by…
low oxygen
3 common pathological conditions associated with Hb
- a-Thalassemia
- B-thalassemia
- sickle cell anemia
a-Thalassemia
- microcytic anemia
- low a-chain synthesis for Hb
B-thalassemia
- microcytic anemia
- low B-chain synthesis for Hb
Sickle cell anemia
- hemolytic nemia
- affects growth development
- E -> V mutation (on beta chain)
Consequences of HbS
- susceptible to hemolysis
- precipitate
- occlude blood vessel -> infarction
