co-transport in

of what? where?

glucose and sodium ions in ileum

why?

To absorb glucose from the lumen to the gut, there must be higher concentration of glucose in lumen compared to epithelial cell (for facilitated diffusion). But there is more in epithelial cell so active transport and co transport is needed.

step 1

Na ions actively transported out epithelial cell into blood which reduced Na ion concentration in epithelial cell

step 2

sodium ions diffuse through co transport protein, from lumen into epithelial cell down concentration gradient, glucose and amino acids also attach and are also transported against their concentration gradient

finally

glucose moves via facilitated diffusion from epithelial cell to blood

adaptations…

inc is SA

inc in no. of proteins channels and carrier molecules in membranes