BIOL 404-Exam 4-GI 9
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How much iron is ingested daily?
How much of the iron ingested is absorbed daily?
When does iron absorption increase?
With need (hemorrhage, growth and pregnancy)
What type of absorption mechanism is used for iron and heme?
Carrier-mediated transporters on the brush border
What regulates iron absorption?
enterocyte ferritin levels
Why are enterocyte ferritin levels important?
They regulate the absorption of iron
What is the most readily absorbed ferrous state?
What state is most dietary iron?
What is an example of a substance that can create a soluble complex with Iron?
How can you increase the solubilty of Iron?
Gastric acid solubilizes iron allowing soluble ascorbate complexes to increase absorption
Apoferritin globular protein of 224 sub-units surrounds and iron micelle of what size?
Micelle with up to 4500 iron atoms
Describe the process of Iron uptake:
- Iron binds to iron binding protein
- Taken into cell
- Binds to Ferritin
- Some is released into the interstitum
- Enters the blood
Higher ferritin levels min the cell mean what to iron absorption?
Less iron is absorbed into the blood
How is the iron binding protein and iron complex absorbed into the cell?
Mediated transport system
Only about ______% of ingested iron is absorbed into the bloodstream.
What intracellular component regulates the amount of iron absorbed?
What happens to most of the iron bound to ferritin?
It is released back into the intestinal lumen when the intestinal cells disintegrate
How often do cells disentigrate?
Every 5 days
Where is most iron excreted?
In the feces
Under conditions of iron need, how is more iron absorbed?
Less ferritin is synthesized so that more iron is absorbed into the bloodstream
Under what conditions would you expect Ferritin levels to be low?
When iron need is increased
The presence of food or chye in the GI can cause what three process to change?
- Secretion of digestion juices
- Blood flow to the tissues
What are the general functions of the GI tract?
Supply nutrients to the body and to remove non digestible material
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