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Exocytosis

The process by which cells release substances (like waste or proteins) to the outside by forming a vesicle that fuses with the cell membrane.

Endocytosis

The process by which cells take in substances from the outside by engulfing them into a vesicle.

Tonicity

Describes the concentration of solutes in a solution compared to another solution.

Isotonic

Equal solute concentration inside and outside the cell.

Hypotonic

Lower solute concentration outside the cell, so water enters the cell.

Hypertonic

Higher solute concentration outside the cell, so water leaves the cell.

Osmosis

The movement of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration.

Diffusion

The movement of molecules (like gases or small particles) from an area of high concentration to an area of low concentration.

Extracellular Fluid

The fluid outside the cells, including blood plasma and interstitial fluid.

Intracellular Fluid

The fluid inside the cells, also called cytoplasm.