Active transport

• What is active transport?


  The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.
• What is ATP used for in active transport?


  Release energy to directly move molecules.
• How does it differ to passive forms of transport?


  Metabolic energy in the form of ATP is needed.

  Substances are moved against a concentration gradient.

  The process is very selective.

  Carrier proteins which act as 'pumps' are involved.
• What is the role of carrier proteins in active transport?

  They bind molecules or ions for transport
• How do carrier proteins bind to molecules or ions?

  By receptor sites on one side of the membrane
• What happens to ATP during the active transport process?

  It splits into ADP and a phosphate molecule
• What is the effect of ATP binding to carrier proteins?

  It causes the protein to change shape
• What happens to the molecule or ion after the protein changes shape?

  It is released to the other side of the membrane
• What occurs after the molecule or ion is released?

  The phosphate molecule is released from the protein
• What happens to the protein after the phosphate is released?

  It reverts to its original shape
• How is ATP regenerated during the process?

  Phosphate recombines with ADP to form ATP
• What are the steps of active transport for a single molecule or ion?

  1. Carrier proteins bind to molecules/ions.
  2. ATP binds to proteins, splitting into ADP and phosphate.
  3. Protein changes shape, opening to the opposite side.
  4. Molecule/ion is released to the other side.
  5. Phosphate is released, protein reverts to original shape.
  6. Phosphate recombines with ADP to form ATP.