the movement of ions or molecules across a cellular membrane from a lower to a higher concentration, requiring the consumption of energy.
Origin of active transport
First recorded in 1960–65
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
biochem physiol a process by which molecules are enabled to pass across a membrane from a region in which they are in a low concentration to one of high concentration; this requires the expenditure of energy in metabolism and is assisted by carrier proteins, commonly referred to as pumps
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
The passage of ions or molecules across a cell membrane against an electrochemical or concentration gradient, or against the normal direction of diffusion.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
The movement of ions or molecules across a cell membrane in the direction opposite that of diffusion, that is, from an area of lower concentration to one of higher concentration. Active transport requires the assistance of a type of protein called a carrier protein, using energy supplied by ATP.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.