Final answer:
The plasma membrane is more permeable to water than simple diffusion through the lipid bilayer alone can explain due to the presence of aquaporins. These are channel proteins that facilitate the rapid transport of water, allowing for efficient water movement across the membrane.Option 1 is the correct answer.
Step-by-step explanation:
Many cells are much more permeable to water than can be explained by simple diffusion through the lipid bilayer because their plasma membrane contains aquaporins. Aquaporins are specialized channel proteins that facilitate the rapid transport of water across the cell membrane. This process is a form of passive transport known as facilitated diffusion, which does not require energy. Aquaporins allow water molecules to bypass the hydrophobic interior of the lipid bilayer, providing a hydrated pathway that increases the permeability of the membrane to water. The discovery of aquaporins was so significant that it led to Peter Agre receiving the Nobel Prize in Chemistry in 2003.
The heightened permeability of many cells to water, surpassing expectations based on simple lipid bilayer diffusion, is attributed to aquaporins within their plasma membranes. These specialized channel proteins expedite the swift transport of water, constituting a form of passive transport termed facilitated diffusion, which operates without energy expenditure. Aquaporins serve as conduits, enabling water molecules to traverse the hydrophobic lipid bilayer's interior, presenting a hydrated pathway that markedly enhances membrane permeability to water. The pivotal discovery of aquaporins earned Peter Agre the 2003 Nobel Prize in Chemistry, underscoring the profound impact of this revelation on our understanding of cellular transport mechanisms and membrane dynamics.