Facilitated diffusion across the

cell membrane

While

water molecules can pass through the cell membrane by simple diffusion, the

rate of transport is very low. However, this slow diffusion cannot account for

the rapid water movement observed in cells. To facilitate efficient water

transport, cells rely on a specialized channel protein called aquaporin.

Refer

to the figure below and choose the correct answers. 

(Note: The figure displays

amino acid labels along the aquaporin channel. For example, 'H' represents the

amino acid Histidine, and 'N' represents Asparagine. The numbers 180 and 192

indicate the positions of these amino acid residues within the aquaporin

protein sequence.)