Transport (biology)

Transport is the movement of molecules, ions, fluids, or particles within an organism or across a biological membrane. It occurs through processes ranging from passive diffusion to energy-dependent pumping and bulk flow.

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Diffusion: The net movement of particles from higher concentration to lower concentration through random motion. It moves substances down concentration gradients without requiring cellular energy.
Concentration gradient: A spatial difference in the concentration of a substance. It provides the driving force for diffusion and shapes transport direction.
Circulatory system: An organ system that moves blood or other circulating fluid through an organism. It distributes transported gases, nutrients, wastes, and signals over long distances.
Passive transport: Movement across a membrane down an electrochemical gradient without direct energy input. It contrasts with active transport, which can move substances against gradients.
Cystic fibrosis: An inherited disease caused by defective CFTR chloride channels, affecting mucus and other secretions. Impaired epithelial ion transport disrupts water movement and thickens mucus.
Osmosis: The net movement of water across a selectively permeable membrane in response to differences in water potential. It is water transport driven by a difference across a membrane.
Electrochemical gradient: The combined effect of a concentration difference and an electrical potential difference on an ion. It predicts whether ions tend to cross a membrane and in which direction.
Xylem: Vascular plant tissue that conducts water and dissolved minerals from roots toward shoots. It carries water through plants by pressure-driven flow and related forces.
Primary active transport: Active transport that directly uses energy, commonly from ATP hydrolysis, to move substances across membranes. It is the direct ATP-powered form of membrane transport.
Cystic fibrosis transmembrane conductance regulator: A membrane protein that functions as an ATP-regulated chloride and bicarbonate channel. It links a specific channel defect to altered epithelial transport.