What is the role of aquaporins in water transport?

Aquaporins are proteins that facilitate the rapid transport of water across cell membranes.

Aquaporins, also known as water channels, play a crucial role in maintaining the water balance within cells and across tissues. They are integral membrane proteins that form pores in the cell membrane, allowing water molecules to move in and out of the cell more efficiently than they would by simple diffusion. This is particularly important in tissues where rapid water movement is necessary, such as in the kidneys, eyes, and salivary glands.

The structure of aquaporins is such that they selectively allow water molecules to pass through, while preventing the passage of ions and other solutes. This selectivity is achieved through a narrow pore in the centre of the protein, which is lined with amino acids that interact favourably with water. The size and shape of this pore is just right to allow a single file of water molecules to pass through, while excluding larger molecules and ions.

Aquaporins are regulated by the cell in response to changes in the cellular environment. For example, in response to dehydration, cells may increase the number of aquaporins in their membranes to facilitate water uptake. Conversely, in conditions of water excess, cells may decrease the number of aquaporins to limit water entry.

In summary, aquaporins are essential for the efficient transport of water across cell membranes. They are highly selective, allowing only water molecules to pass through, and their activity is regulated by the cell in response to changes in the cellular environment. Understanding the role of aquaporins in water transport is fundamental to our understanding of cellular function and homeostasis.