Table of Contents
What determines whether water moves in or out of a cell?
The ability of an extracellular solution to make water move into or out of a cell by osmosis is known as its tonicity. Tonicity is a bit different from osmolarity because it takes into account both relative solute concentrations and the cell membrane’s permeability to those solutes.
What causes a cell to move water into and out of a cell or organism?
Water molecules move according to differences in potential energy between where they are and where they are going. Gravity and pressure are two enabling forces for this movement. These forces also operate in the hydrologic (water) cycle.
What determines what passes through a cell membrane?
The ability of a molecule to travel across a membrane depends on its concentration, charge and size. In general, molecules diffuse across membranes from areas of high concentration to low concentration. Cell membranes prevent charged molecules from entering the cell unless the cell maintains an electrical potential.
What determines which substances enter or leave the cell?
plasma membrane
The plasma membrane is the boundary of the cell; it determines what enters and exits the cell, and how it interacts with its environment. Cells are surrounded by fluid, termed extracellular or interstitial fluid.
What causes water to move into cells?
Large quantities of water molecules constantly move across cell membranes by simple diffusion, often facilitated by movement through membrane proteins, including aquaporins. In general, net movement of water into or out of cells is negligible.
How does water move through the cell membrane?
Water transport across cell membranes occurs by diffusion and osmosis. The two main pathways for plasma-membrane water transport are the lipid bilayer and water-selective pores (aquaporins). Aquaporins are a large family of water pores; some isoforms are water-selective whereas others are permeable to small solutes.
Why does water pass quickly through cell membranes?
Water, like many molecules, wants to be at equilibrium; it wants to have an equal concentration on either side of the membrane. When the concentration of water on the outside of the cell is greater than the concentration on the inside, water will quickly move into the cell to even up the concentrations.
How is water transported across the membrane?
How does water enter a cell?
Water moves across cell membranes by diffusion, in a process known as osmosis. Osmosis refers specifically to the movement of water across a semipermeable membrane, with the solvent (water, for example) moving from an area of low solute (dissolved material) concentration to an area of high solute concentration.
How does water pass through the selectively permeable cell membrane?
Water passes through the semipermeable membrane via osmosis. Molecules of oxygen and carbon dioxide pass through the membrane via diffusion.
When water moves out of a cell the cell?
Key terms
| Term | Meaning |
|---|---|
| Osmosis | The net movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration |
| Tonicity | The ability of an extracellular solution to make water move into or out of a cell by osmosis |