Transport of materials across biological membranes

Vocabulary-style flashcards covering key terms related to membrane transport, diffusion, osmosis, and membrane proteins.

Membrane transport

The movement of substances across a biological membrane.

Concentration gradient

A difference in solute concentration across a space that drives diffusion and related transport processes.

Osmosis

The diffusion of water across a selectively permeable membrane toward the side with higher solute concentration.

Hypertonic solution

A solution with higher solute concentration than the cell’s interior, causing water to move out and the cell to shrink.

Hypotonic solution

A solution with lower solute concentration than the cell, causing water to move in and the cell to swell.

Isotonic solution

A solution with the same solute concentration as the cell, resulting in no net water movement.

Simple diffusion

Passive movement of small nonpolar molecules directly through the lipid bilayer down a concentration gradient.

Facilitated diffusion

Passive diffusion via membrane proteins (channel or carrier) that speeds transport down its concentration gradient.

Channel protein

A transmembrane protein that forms a pore for ions or water to cross the membrane, typically by facilitated diffusion.

Carrier protein

A transmembrane protein that binds a specific molecule and changes shape to shuttle it across the membrane, usually by facilitated diffusion.

Aquaporin

A channel protein that facilitates rapid water movement across the membrane.

Pump

A membrane protein that uses energy to move substances against their concentration gradient (active transport).

Diffusion

Movement of molecules from high to low concentration; can be simple or facilitated.

Osmotic movement

Movement of water driven by differences in solute concentration; part of osmosis.

Crenation

Shrinkage of red blood cells in a hypertonic solution due to water leaving the cell.

Active transport

Movement of substances against their concentration gradient that requires energy (often ATP) and membrane proteins (pumps).