Question

select the true statements. water molecules move down their concentration gradient. osmosis uses cellular energy. water molecules can cross the cell membrane by simple diffusion. water molecules can cross the cell membrane by facilitated diffusion.

Explanation:

• Water molecules move down their concentration gradient: Osmosis is the movement of water from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration), which is moving down the concentration gradient.
• Osmosis uses cellular energy: Osmosis is a passive transport process. Passive transport does not require cellular energy (such as ATP). Active transport (e.g., sodium - potassium pump) requires cellular energy.
• Water molecules can cross the cell membrane by simple diffusion: Although the cell membrane is made of a lipid bilayer (non - polar), water (a small polar molecule) can cross the membrane in small amounts by simple diffusion.
• Water molecules can cross the cell membrane by facilitated diffusion: Aquaporins are channel proteins that allow water molecules to cross the membrane more rapidly. This is an example of facilitated diffusion (a type of passive transport where a protein channel helps in the movement of molecules down their concentration gradient).

Answer:

• Water molecules move down their concentration gradient.
• Water molecules can cross the cell membrane by simple diffusion.
• Water molecules can cross the cell membrane by facilitated diffusion.