osmosis

Osmotic Solutions

• Isotonic Solution

• Hypertonic Solution

• Hypotonic Solution

isotonic solution

one that has the same concentration of solutes both inside and outside the cell.

hypertonic solution

is one that has a higher solute concentration outside the cell than inside.

hypotonic solution

one that has a higher solute concentration inside the cell than outside

Endosmosis

When a substance is placed in a hypotonic solution, the solvent molecules move inside the cell and the cell becomes turgid or undergoes deplasmolysis.

Exosmosis

When a substance is placed in a hypertonic solution, the solvent molecules move outside the cell and the cell becomes flaccid or undergoes plasmolysis.

Semipermeable membrane

The cell membrane allows water to pass through but restricts many solutes (salts, sugars, proteins)

Unequal Solute Concentrations

When one side of the membrane has more solute a concentration difference is created

Water movement

Water molecules move through the membrane often with special protein channels called aquaporins, toward the side with the higher solute concentration

Equilibrium

Movement continues until the concentrations of water and solutes become balanced on both sides.

Diffusion (NO ATP)

moves particles from higher to lower concentration without requiring energy.

Facilitated Diffusion

moves down a concentration gradient but requires a protein carrier because the substance cannot cross the membrane easily.

Osmosis (NO ATP)

the movement of water across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration

• high concentration of water molecules

• Lower concentration of water molecules