EVERYDAY SCIENCE

Detailed explanation-1: -Because of the slow diffusion of water across the lipid bilayer, aquaporins effectively increase the overall rate of water movement across the cell membrane.

Detailed explanation-2: -In order to allow water to move in and out, cells have special proteins that act as a doorway. These proteins are called aquaporins (aqua = water, porin = pore).

Detailed explanation-3: -Water can pass through biological membranes via two pathways: simple diffusion through the lipid bilayer, or water-selective facilitated diffusion through aquaporins (AQPs).

Detailed explanation-4: -The movement of water through the aquaporins is driven by osmotic gradients. For example, red cells dropped into seawater will shrink because water leaves the cells; red cells dropped into fresh water will swell and explode since water enters the cell.

Detailed explanation-5: -Aquaporins (AQP) are integral membrane proteins that serve as channels in the transfer of water, and in some cases, small solutes across the membrane. They are conserved in bacteria, plants, and animals. Structural analyses of the molecules have revealed the presence of a pore in the center of each aquaporin molecule.