Final answer:
Aquaporins are channel proteins that allow water to move across cell membranes, aiding in osmosis and water balance within the body. They are critical in biological processes and involved in various genetic diseases.
Step-by-step explanation:
Aquaporins are specific channel proteins that facilitate the movement of water across a selectively permeable membrane, thereby permitting osmosis. These proteins allow water molecules to move through the plasma membrane at a very high rate. Aquaporins play a crucial role in maintaining water balance within cells, and their discovery was significant enough to warrant a Nobel Prize in Chemistry. While some aquaporins are exclusive to water, others also support the transport of substances like glucose, glycerol, and ions. The size of aquaporin channels is so precise that they generally exclude all but water molecules, thus effectively regulating water flow in and out of cells.
The presence of aquaporins is widespread in human cells, with notable concentrations in red blood cells and kidney tubules, emphasizing their importance in processes like urine concentration. In the kidney, aquaporins can be regulated by hormones such as ADH to control water reabsorption into the blood and maintain the body's fluid balance. Their significance in biology and medicine is highlighted by the fact that mutations in aquaporin genes have been linked to several genetic diseases.