Membrane Transport and Tonicity

Passive transport

Movement of substances along an existing gradient without the direct use of ATP.

Active transport

Movement of substances against a gradient that requires cellular energy, typically ATP.

Simple diffusion

Movement of molecules from high concentration to low concentration without energy, suitable for small or lipid-soluble particles.

Osmosis

The movement of water across a semipermeable membrane from low solute concentration to high solute concentration, following the solute.

Facilitated diffusion

Transport of substances from high concentration to low concentration with the help of a channel or carrier protein, and without ATP.

Filtration

The movement of water and small solutes across a membrane driven by a pressure gradient.

Hypertonic solution

A solution with a higher concentration of solutes than the cell cytoplasm, causing the cell to lose water and potentially shrink.

Hypotonic solution

A solution with a lower concentration of solutes than the cell cytoplasm, leading to water entering the cell and potentially causing it to swell or burst.

Isotonic solution

A solution with equal concentrations of solutes inside and outside the cell, resulting in no net movement of water.

Concentration gradient

The difference in concentration of a substance across a space, affecting the direction of diffusion.