Final answer:
Osmosis occurs through water channel proteins known as aquaporins, which allow for the rapid and efficient passage of water molecules across cell membranes.
Step-by-step explanation:
Osmosis refers to the diffusion of water across a semipermeable membrane. This process can occur through water channel proteins, which are specifically known as aquaporins. These proteins facilitate the rapid and efficient movement of water molecules across cell membranes and are crucial for maintaining the water balance within cells. Aquaporins are a type of channel protein that, unlike some other proteins that transport various molecules, predominantly allow for the passage of water.
In addition to simple diffusion across the lipid bilayer, water also passes through these membrane proteins in a process known as facilitated diffusion. This means that while some water molecules can slip between the lipid tails of the cell membrane, the presence of aquaporins significantly increases the rate at which water can move in response to osmotic pressure, which is the flow from an area of low solute concentration to an area of high solute concentration.
The discovery of aquaporins was so pivotal to our understanding of cellular water balance that it earned Peter Agre the Nobel Prize in Chemistry in 2003. Since then, various genetic diseases have been linked to mutations in aquaporin genes. This highlights the importance of these proteins in physiological processes and the health of organisms.