Absorption of minerals, vitamins and water
Absorption of minerals
Sodium is transported as sodium co-transport along with glucose and amino acids and Sodium is also coupled transported with chloride ion
Sodium ion also shows diffusion across the electrochemical gradient.
Potassium is transported by passive diffusion across the concentration gradient
Bicarbonate ions are transported actively or rarely with sodium ion.
Magnesium ion is transported actively, but poorly absorbed.
Calcium ion is als transported actively by the calcium-binding protein produced under the influence of vitamin D3
Phosphorous is actively absored related to calcium absorption.
Copper ion is absorbed in small quantities.
Cobalt and manganese ions are readily absorbed.
Iron absorption is related to its level in mucosal cells and is mediated by apoprotein carriers.
Absorption of water
Water is transported or absorbed passively in GI tract.
Absorption of vitamins
Fat soluble vitamins (A, D, E, K) pass through the intestinal mucosa by passive diffusion. Water soluble vitamins (except B12) are also absorbed by passive diffusion but may also be transported actively.
Vitamin B12 requires an intrinsic factor, secreted by the gastric glands of the stomach, for its absorption by and active transport process.