GI 18 Flashcards
What are the water soluble vitamins?
- Vitamin C
* B Complex vitamins
Where are the majority of water soluble vitamins absorbed?
In the first part of the small intestine
What is the absorption of majority of water soluble vitamins coupled to?
Specific sodium cotransporters
What is Folate absorption dependant on?
A proton-coupled folate transporter
Where does B12 absorption occur?
In the ileum
What does B12 absorption require?
Binding to a protein called intrinsic factor
What are the fat soluble vitamins?
Vitamins A, D, E, and K
How are fat soluble vitamins typically consumed?
Bound as esters
What must happen to the esters bound to fat soluble vitamins?
The esters must be hydrolyzed in the gut lumen
How does uptake of free fat soluble vitamins usually occur?
Via specific transport proteins
What happens to free fat soluble vitamins after being absorbed?
They are re-esterified and packaged into chylomicrons
Where is the majority of the body’s iron present?
In hemoglobin
How must lost iron be replaced?
From the diet
What does tight regulation of iron absorption mean?
That the amount taken up matches what is lost so not a lot is absorbed by the body
What is the form of iron of most of the iron in the diet?
Fe3+, the ferric form
Which form of iron is absorbed?
Fe2+, the ferrous form
What converts the ferric form of iron to the ferrous form?
Ferric reductase in the brush border of the epithelium
What is the uptake of Fe2+ into enterocytes facilitated by?
DMT1 (divalent metal transporter 1)
What happens once Fe2+ is inside the enterocytes?
Some Fe2+ is stored bound to ferritin and the remain is transported out of the cell and into the circulation
What is export of Fe2+ out of the enterocyte and into the circulation facilitated by?
The basolateral transporter ferroportin 1 (FP)
What happens to Fe2+ when it gets to the circulation?
Fe2+ is converted to Fe3+ which binds to transferrin
