Osmosis and Tonicity Lab – Vocabulary Flashcards

Vocabulary flashcards covering key osmosis, tonicity, and lab concepts from the lecture notes.

Osmosis

Movement of solvent (water) through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration, driven by kinetic energy; no external energy required.

Solute

A dissolved substance in a solution (e.g., sugars, salts).

Semipermeable membrane

A membrane that allows passage of some substances (such as water and small molecules) but restricts larger or polar molecules like ions, proteins, and polysaccharides.

Tonicity

The effect of a solution on cell volume, related to osmolarity; influenced only by solutes that cannot cross the membrane, which exert osmotic pressure.

Hypertonic

A solution with a higher solute concentration than the cell interior; water moves out of the cell and it shrinks.

Isotonic

A solution with the same solute concentration as the cell interior; no net water movement and no change in cell size.

Hypotonic

A solution with a lower solute concentration than the cell interior; water enters the cell, which may swell and burst (cytolysis).

Osmolarity

The total concentration of solutes in a solution per unit volume; used to compare solutions for tonicity.

Osmotic pressure

The pressure required to prevent osmosis; generated by solutes that cannot cross the membrane to draw water across.

Cytolysis

The bursting or lysis of a cell due to excessive water uptake in a hypotonic environment.

Osmoregulation

Biological process of maintaining stable internal water and solute balance in organisms (e.g., fish in marine or freshwater).

Dialysis tubing

Semipermeable tubing used in experiments to model cell membranes and study osmosis by separating inside and outside solutions.

Aqueous cytoplasm

The water-based interior solution of a cell (inside the dialysis tubing in the lab), containing dissolved solutes.

Extracellular environment

The solution surrounding the cell/tube, whose tonicity determines water movement across the membrane.

Membrane permeability

Selective permeability of cell membranes: typically impervious to large/polar solutes (ions, proteins, polysaccharides) but permeable to small nonpolar or polar molecules such as O2, CO2, N2, NO and many small solvents like water.

Freshwater fish osmoregulation

Adaptation to hypotonic environments: water tends to enter the body; they urinate constantly to excrete excess water and avoid cytolysis.

Saltwater fish osmoregulation

Adaptation to hypertonic environments: they drink seawater and actively excrete the excess salt to maintain balance (water loss via osmosis).