tonicity and osmoregularity

Osmosis

The passive diffusion of water across a selectively permeable membrane from an area of higher water potential to an area of lower water potential.

Selectively Permeable Membrane

A membrane that allows certain molecules or ions to pass through freely while restricting others.

Concentration Gradient

The gradual difference in the concentration of a solute across a spatial area or membrane.

Aquaporins

Specialized channel proteins embedded in the cell membrane that facilitate the rapid, passive movement of water molecules.

Tonicity

The relative solute concentration of an external solution compared to the inside of a cell, which dictates the direction of net water movement.

Hypotonic Solution

A solution with a lower solute concentration than the cell's cytoplasm, causing water to rush into the cell.

Hypertonic Solution

A solution with a higher solute concentration than the cell's cytoplasm, causing water to flow out of the cell.

Isotonic Solution

A solution where the external and internal solute concentrations are equal, resulting in no net movement of water.

Lysis

The bursting of an animal cell when placed in a hypotonic solution due to excessive water intake.

Crenation

The shrinking of an animal cell when placed in a hypertonic solution due to water loss.

Turgid

A firm and healthy plant cell state held rigid by internal turgor pressure against the cell wall in a hypotonic solution.

Plasmolysis

The process in plant cells where the plasma membrane pulls away from the cell wall as water leaves in a hypertonic solution.

Flaccid

A limp plant cell state that occurs in an isotonic solution due to lack of turgor pressure.

Osmoregulation

The physiological process by which organisms regulate internal water balance and solute concentrations to maintain homeostasis.

Contractile Vacuole

An osmoregulatory organelle found in freshwater protists that rhythmically collects and pumps out excess water to prevent bursting.

Central Vacuole

A large organelle in plant cells that stores water and solutes, playing a key role in maintaining turgor pressure.