Active Transport

A few ions or molecules are transported across the membrane against their concentration gradient, i.e., from lower to higher concentration. Such type of transport is called active transport because it is an energy-dependent process in which ATP is utilised, e.g., Na+/K+ pump.

  • Active transport uses energy to pump molecules against a concentration gradient.
  • Active transport is carried out by membrane-bound proteins. Hence, different proteins in the membrane play a major role in both active as well as passive transport.
  • Cells undergoing active transport bear abundant mitochondria to provide ATP, needed to power active transport. Pumps are protein which can transport the substances.
  • Active transport shows uphill transport because in this case movement can occur from lower to a higher concentration.
  • Carrier proteins are highly specific like enzymes for substances to be carried across the membrane.
  • Inhibitors can inhibit the process by reacting with a protein side chain.
  • When all the protein carriers are in use or saturated with substances to be carried, transport rate reaches its maximum
  • The movement of ions from soil to the interior of the root is against a concentration gradient and requires a mode of active transport.
  • As glucose is prepared at the source (by photosynthesis), it is converted to sucrose (a disaccharide). The sugar is then moved in the form of sucrose into the companion cells and then into the living phloem sieve tube cells by active transport
  • Active transport is necessary for living cells because certain substances must be concentrated and others must be excluded. Active uptake of minerals by roots mainly depends on the availability of oxygen.


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