• Describe the modifications to the proximal tubule epithelia which maximise transport.

microvilli =inc SA

Deep infoldings of the basolateral membrane which increase SA for transporters

rich supply of mitochondria = more ATP production

• Describe the transport processes in the Proximal Tubule enabling Na+, K+ and H2O reabsorption.

NA reabsorption

low Na+ inside cell maintained by Na+/K+ ATPase on basolateral membrane and Na+ is extruded back to blood

K+ leaks back to blood

which causes a gradient for Na+ to enter via apical membrane

transcellular route requires channels/transporter

paracellular pathway requires leaky tight junctions

other molecules can also be absorbed and excreted during these Na+ gradients