Ions, vitamins and minerals Flashcards
What are some examples of primary active transporters?
Na/K ATPase
H/K ATPase
What are some examples of secondary active transporters?
SGLT-1 - uses Na gradient to take up glucose
HCO3-/Cl- counter-transport
Na+/H+ counter transport
What are some examples of facilitated transport/diffusion?
GLUT-5 -
GLUT-2
Where does the greatest amount of water get absorbed?
Jejunum Small intestine absorbs 8 lirtes - saliva - gastric secretions - pancreas - bile - water - intestine
how is water abosrobed?
Standing gradient osmosis
the absorption of water is powered by absorption of ions
Na+ —-
It is then pumped out of the cells that it is in in exchange for K+ and this creates a high conc of Na+ near basement membrane. electrochem grad changes so Cl- and HCO3- move out as well, drives H2O absorption via both para and transcellular paths
How is Na+ absorbed?
- counter transport with H+ bowel
- cotransport with monosac - jej Cl- - ileum
- ion channel colon
How are K+ and Cl- absorbed?
K+ diffuses via paracellular pathways - small intestine transcellular in colon Cl- cotransport with na+ in the ileum Exchanged for HCO3 in the colon
Where is calcium absorbed? What increases it?
In the duodenum and ileum
deficiency increases ability to absorb
PTH and Vit D increase absorption
How is calcium absorbed?
Intestinal calcium-binding protein
- fac diff
Ion channel
Why is ca2+ low in the cell? how is Ca2+ brought in while maintaining this low conc? how is it then pumped into the blood?
Acts as a signalling molecule
- Constant intake might cause loops of secondary messenger
calcium is bound to CALBINDIN to prevent action as intracellular signal and then moved into blood
Has to be pumped as against concentration gradient
- plasma membrane Ca ATPase
- High affinity but sklow but lowers conc in cell
- Na/Ca exchanger
- Low affinity, needs lots of Ca but v fast
Why is Vit D needed for Ca uptake?
Enhances transport of Ca2+ thru cytosol
Increases calbindin levels
Increases rate of extrusion on BM - increases levels of PMCA
Why is iron absorbed??
Needed as is e- donor, acceptor
Ox transport
Ox phos
but, is toxic in excess and no active excretion mechanism
- so, mediate it
How is iron present in the diet?
inorganic iron, haem group - Hb etc
Why must Ffe2+ be absorbed?
Fe3+ has to be reduced to Fe2+ because body can’t absorb Fe3+
This is done by Vit C
What does Fe3+ form
Insoluble salts with OH, Po4 and HCO3