active transport

• Active transport


  Movement of molecules/ions in or out of cell from region of lower concentration to region of higher concentration using ATP and carrier proteins against concentration gradient
• How active transport works

  1. Molecule/ion attaches to receptor site on carrier protein

  2. Molecule of ATP binds to carrier protein

  3. ATP molecule undergoes hydrolysis-produces phosphate + ADP

  4. Phosphate attaches to carrier protein-causes it to change shape

  5. Shape change causes carrier protein to transport molecule/ion to other side of membrane where it's released

  6. Phosphate leaves carrier protein - returns to previous shape
• ADP & phosphate later reforms ATP during respiration
• Active transport uses a lot of ATP
• There are lots of mitochondria in cells that carry out active transport
• Carrier proteins used in active transport


  • They are specific (each will only transport one molecule/ion type)
• Antiporter


  Movement of two molecules in opposite directions through protein channel
• Symporter


  Movement of two molecules in the same direction
• Uniporter


  Movement of one molecule independent of others