Which of the following allows water to move much faster across cell membranes?

• A. Cholesterol
• B. Aquaporins
• C. Glycoproteins
• D. Phospholipids

Answer: (B)

Verified step by step guidance

1. Understand the structure of the cell membrane: The cell membrane is primarily composed of a phospholipid bilayer, which acts as a barrier to most water-soluble substances.
2. Identify the role of aquaporins: Aquaporins are specialized channel proteins embedded in the cell membrane that facilitate the rapid transport of water molecules across the membrane.
3. Differentiate between aquaporins and other membrane components: While cholesterol, glycoproteins, and phospholipids are important components of the cell membrane, they do not specifically facilitate the rapid movement of water like aquaporins do.
4. Consider the mechanism of water transport: Water molecules move through aquaporins via osmosis, which is the passive movement of water from an area of lower solute concentration to an area of higher solute concentration.
5. Conclude the function of aquaporins: Aquaporins significantly increase the permeability of the cell membrane to water, allowing water to move much faster across the membrane compared to diffusion through the lipid bilayer alone.