active transport (redirected from Biological transport, active)

transport /trans·port/ (trans´port) movement of materials in biological systems, particularly into and out of cells and across epithelial layers.

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active transport  movement of materials in biological systems resulting directly from expenditure of metabolic energy.

(A) Passive transport exemplified by diffusion of potassium ions across the plasma membrane, through specific ion channels, down a concentration gradient; (B) active transport exemplified by the cellular sodium pump, which uses ATP hydrolysis to create gradients of sodium and potassium across the plasma membrane.

bulk transport  the uptake by or extrusion from a cell of fluid or particles, accomplished by invagination and vacuole formation (uptake) or by evagination (extrusion); it includes endocytosis, phagocytosis, pinocytosis, and exocytosis.

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active transport

n.

The passage of ions or molecules across a cell membrane against an electrochemical or concentration gradient, or against the normal direction of diffusion.

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active transport,

the movement of materials across the membranes and epithelial layers of a cell by means of chemical activity that allows the cell to admit otherwise impermeable molecules against a concentration gradient. Expediting active transport are carrier molecules within the cell that bind and enclose themselves to incoming molecules. Active transport is the means by which the cell absorbs glucose and other substances needed to sustain life and health. Certain enzymes play a role in active transport, providing a chemical "pump" that typically uses adenosine triphosphate (ATP) to help move substances through the plasma membrane. Compare osmosis, passive transport.

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active transport [ak´tiv trans´port]

the movement of ions or molecules across cell membranes and epithelial layers, usually against a concentration gradient, as a direct result of the expenditure of metabolic energy. For example, under normal circumstances more potassium ions are present within the cell and more sodium ions are present extracellularly. The process of maintaining these normal differences in electrolytic composition between the intracellular and extracellular fluids is active transport. The process differs from passive transport, simple diffusion, and osmosis in that it requires the expenditure of metabolic energy.

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transport,

n the movement of biochemical substances from one site to another.

transport, active,

n transport of substances through membranes or epithelium, requiring metabolic energy.

transport, passive,

n transport along a gradient without the use of metabolic energy.

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active

not passive.

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active principle

the drugs or chemicals in a pharmaceutical preparation that exert an effect pharmacologically; as distinct from the inert fillers, wetting agents and other excipients also often included.

active site

that region of a protein, usually an enzyme, that binds to another molecule such as the substrate of the enzyme.

active transport

the movement of ions or molecules assisted by a carrier protein across the cell membranes and epithelial layers, usually against a concentration gradient, resulting directly from the expenditure of metabolic energy. For example, under normal circumstances more potassium ions are present within the cell and more sodium ions extracellularly. The process of maintaining these normal differences in electrolytic composition between the intracellular fluids is active transport. The process differs from simple diffusion or osmosis in that it requires the expenditure of metabolic energy.

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transport

1. movement of materials in biological systems, particularly into and out of cells and across epithelial layers.

2. transport of animals, see transit, transportation.

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active transport

see active transport.

transport death

death during transportation, e.g. porcine stress syndrome.

transport host

see paratenic host.

transport media

see transport medium.

membrane transport proteins

specific proteins associated with the plasma membrane of cells that are responsible for transferring solutes including ions, sugars, amino acids, nucleotides and many metabolites across cell membranes.

transport myopathy

see exertional rhabdomyolysis.

transport stress

stress imposed by lack of access to water and feed, physical exhaustion caused by standing for long periods, heat stress, aggression by other animals.

transport tetany

see transit tetany.

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transport, active 

A process by which particles (e.g. ions, molecules) are transported across cell membranes, against, in almost all instances, the concentration gradient. It requires energy, which is provided by the metabolism of carbohydrates, proteins or lipids and cellular energy, which is obtained from splitting adenosine triphosphate (ATP).(Example: the sodium/ potassium pump that keeps sodium ions out of a cell and potassium ions in). When this process results in a compound being released, it is termed 'secretion'. This process is one of the mechanisms by which aqueous humour is produced in the ciliary body. See action potential; ultrafiltration.