RBC Wed Prereading Flashcards
(33 cards)
List some major sources of iron
red meat, shellfish, fish-heme iron
enriched cereals, beans, tofu, seeds, potatoes, green veggies, dried fruit-non heme iron
When are plasma hepcidin levels high?
when stores are full of iron and erythropoietic activity is normal
What does high plasma hepcidin cuase?
downregulation of ferroportin and trapping of most of the absorbed iron
When are plasma hepcidin levels low?
when body iron stores are depleted or erythropoiesis is stimulated
What happens when hepcidin leves are low?
ferroportin activity increases, allowing a greater fraction of absorbed iron to be transferred into plasma transferrin
What protein allows for entry of non-heme iron?
DMT-1 divalent metal transporter 1
What protein allows for entry of heme?
heme transporter
What cofactor is required for the asorption of non-heme iron?
vitamin C
What enzyme reduces ferric to ferrous? What is it dependent on?
duodenal cytochrome B ascorbic acid (vit C)
What stores iron in dueodenal cells?
ferritin
What transports ferrous across the basal later membrane of duodenal cells?
ferroportin 1
What converts ferrous back to ferric once it has crossed the basal lateral membrane?
hephaestin
What molecule transports ferric in the blood?
transferrin
How do other cells take up ferric?
transferrin receptor–>endocytosis–>DMT1 to get out of endosome
What molecule regulates the release of iron from the duodenal epithelial cells?
hepcidin
What are hemosiderin granules?
partially degraded ferritin-iron complexes
this is the main storage form for iron during overload
How is iron recycled?
by marophages
What are major ways iron is lost?
shedding of intestinal/skin cells
menstruation
abnormal bleeding
pregnancy
What is the cause of megaloblastic anemai?
inability to synthesize adequate amounts of purines and thymidylate triphosphate for DNA synthase
folate def, vit B12 def, methionine synthase def
What effect does methyltrexate have on purine synthesis?
inhibits dehydrofolate reductase, limiting puruine and thymidylate synthesis
causes drug induced megaloblastic anemia
Sources of folate
veggie (esp dark green)
fruits, grains, nuts, beans, dairy, seafood, meat
cereal, rice
sources of vitamin B12
meat, shellfish, milk, eggs
vegans must get supplement
What role does saliva play in B12 uptake?
Salivary haptocorrin/R protein needed
What cells secrete intrinsic factor?
parietal cells
