Active transport

Substances are transported passively down concentration gradients in diffusion and osmosis. Often, substances have to be moved from a low to a high concentration - against a concentration gradient.

Active transport is a process that is required to move molecules against a concentration gradient. The process requires energy.

  • Energy for the process is acquired from the breakdown of glucose using oxygen in aerobic respiration.
  • ATP is produced during respiration and releases the energy for active transport.

For plants to take up mineral ions, ions are moved into root hairs, where they are in a higher concentration than in the dilute solutions in the soil. Active transport then occurs across the root so that the plant takes in the ions it needs from the soil around it.

A diagram of the root epidermal cell

In animals, glucose molecules have to be moved across the gut wall into the blood.

  • When glucose concentration in the gut is higher than in the interstitial cells, it moves into them by diffusion.
  • When the glucose concentration in the gut is lower than in the interstitial cells, glucose is transported by active transport out of the gut to ensure all glucose is absorbed.
Active transport in intestine
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