ions, vitamins and minerals lecture Flashcards
(71 cards)
sequential molar concentrations (factor 10^-3)
molar, millimolar, micromolar, nanomolar, picomolar, femtomolar
define diffusion
process where atoms or molecules intermingle due to random thermal motion; fast over microscopic distances, slow over macroscopic differences
purpose of circulatory system in multicellular organisms
bring individual cells within diffusion range
function of cell membrane
act as diffusion barrier so cells can have different cytoplasmic concentrations vs. EC
water potential from low to high
hypotonic (swell), isotonic, hypertonic (shrink)
how do molecules cross epithelium to enter bloodstream
paracellular transport through tight junctions and lateral intercellular spaces; transcellular transport
through epithelial cells in apical membrane
2 types of transport proteins involved in faciliated diffusion or active transport
channel proteins (form aqueous pores - fast), carrier proteins (bind to solute and undergo conformational change - slow)
4 types of gated channel-mediated transport
voltage-gated, EC ligand-gated, IC ligand-gated, mechanically gated
3 types of carrier-mediated transport
uniport, symport (same direction), antiport (opposite direction - equalise charge); secondary active transport
define primary active transport
linked directly to cellular metabolism, using ATP to power transport
define secondary active transport
derives energy from concentration gradient of another substance that is actively transported
effect of facilitated diffusion on rate of substance flowing down concentration gradient
enhances, but tends to equilibrate substance across membrane
how is absorption of glucose and galactose achieved
secondary active transport, with SGLT-1 carrier protein on apical membrane, which can transport glucose against concentration gradient
how is absoprtion of fructose achieved
facilitated diffusion using GLUT-5 carrier protein on apical membrane, which is effective at low concentrations of fructose in lumen as tissue and plasma levels low
how does glucose exit basolateral membrane
facilitated diffusion through GLUT-2 carrier protein (high-capacity, low-affinity); glucose between plasma and enterocyte generally equilibrated as glucose moves out to blood
what requires specific absorption
water and ions, calcium, iron, vitamins (B12)
where is most water absorbed
jejunum in small intestine (small intestine: 8L, colon: 1.4L)
how are most ions slowly absorbed
passive diffusion
source of water
ingest, saliva, gastric secretions, bile, pancreas, intestinal
what drives standing gradient osmosis
Na+ (transported from lumen into enterocyte, which becomes more efficient down intestine)
Na+ absorption in proximal bowel
counter-transport in exchange for H+ (equilibrating charge)
Na+ absorption in jejunum
co-transport with amino acids and monosaccharides
Na+ absorption in ileum
co-transport with Cl- (equilibrating charge)
Na+ absorption in colon
restricted movement through ion channels
