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Yes, water does not pass directly through the phospholipid bilayer of cell membranes. It must have a special protein channel to move through.


The plasma membrane of all cells (archaea, eubacteria, plants, animals, fungi) is made of a double layer of phospholipids, which have tails of hydrophobic (water repelling) fatty acids that aggregate together in the middle of the membrane, and "heads" of a wide variety of phosphate complexes that are hydrophilic (water attracting) and form layers on both the inside and outside of the membrane.This structure forms the basic sheet of membrane that surrounds all cells on their outer surface.Only very small, uncharged, and nonpolar molecules can pass directly through the lipid bilayer structure, because the nonpolar layer of fatty acids tails repels ions (charged atoms or molecules) and molecules of any size that are polar.There are very few molecules small enough to simply diffuse (or float) through this structure.The only examples I can find are nonpolar gas molecules like oxygen, carbon dioxide, and nitrogen.All other molecules must have a specific membrane protein to allow them in or out of cells. These proteins can take various forms (channels, gates, transport mechanisms of multiple types.) Water is a very polar molecule and special channels called aquaporins were discovered in 1990 that allow water molecules to pass through in single file.Since they were first found, hundreds of specific types have been found, including eleven specific types in human cells. Cells that have these channels allow water to diffuse in and out.Cells without them are practically impervious to water.

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Related Questions

Does osmosis move phospholipid bilayer or protein channel?

Osmosis moves water molecules across the phospholipid bilayer of a cell membrane. Protein channels help facilitate the movement of water and other molecules by providing a pathway through the membrane.


What three conditions are needed for osmosis to occur?

Three conditions are needed for osmosis to occur: a semipermeable membrane that allows only water molecules to pass through, a difference in solute concentration on either side of the membrane, and a gradient in water concentration across the membrane.


What is the transport of water across the cell membrane called?

Movement of water across a membrane is called OSMOSIS.


When will water stopping across a membrane?

When will water stop moving across a membrane when the water concentration is equal on both sides.


How is water transported across the membrane?

Water is transported by a passive transport called osmosis. Osmosis is diffusion of water across the membrane.


Does osmosis require membrane proteins?

No, osmosis is a special type of diffusion in which a water molecule is able to passively transport through a membrane without a protein. Although it is polar, it's extremely small size makes this possible


What is aquaporins?

Aquaporins are protein molecules embedded in the phospholipid bilayer (cell membrane ) of some cells. They transport water across the cell membrane.


What are the two things needed for osmosis to take place?

Partially permeable membrane(visking tubing) and water


Water molecules diffuse through a selectively permeable membrane?

Water diffuses by facilitated diffusion, passing through water permeable protein channels embedded in the cell membrane. Water molecules can not pass through the lipid bilayer because water is polar. However, polar molecules pass though the cell membrane through the protein channels. The proteins that aid water in passing through the cell membrane are called aquaporins. "Aqua" for water, and "porin" for pore. A "water pore" in essence.


Materials essential to life processes move across a cell membrane through a variety of methods What cell membrane structure allows water-soluble materials to be passively transported to the cytoplasm?

Protein channels known as aquaporins allow water molecules and other water-soluble materials to pass through the cell membrane via passive transport. Aquaporins form water channels that regulate the flow of water across the membrane, facilitating the movement of essential molecules into the cell.


What is the protein that reduce water loss at the skin surface?

The protein that reduces water loss at the skin surface is called aquaporin. Aquaporins are membrane proteins that facilitate the transport of water across cell membranes, helping to maintain hydration and prevent excessive water loss from the skin.


How do water-soluble molecules diffuse through the cell membrane?

Water-soluble molecules diffuse through the cell membrane by passing through protein channels or transporters that are embedded in the membrane. These channels and transporters allow the molecules to move across the membrane, from an area of high concentration to an area of low concentration, without requiring energy.