2.6.4 Active Transport & Co-Transport

• Active transport = movement of molecules against a concentration gradient using carrier proteins, requiring ATP hydrolysis
• Coupled with the hydrolysis of ATP
• Co-transport = Movement of two molecules, one going down their concentration gradient the other going against the concentration gradient
• Absorption of Glucose via the small intestine/ileum

  1. Here sodium and potassium ions are pumped out of the epithelial cell by active transport into the blood leaving a lower concentration in the cell. 
  2. This causes these ions to move in from the lumen by facilitated diffusion, which at the same time brings glucose and amino acids into the cell.
  3.  These then diffuse from a high concentration in the epithelial cell to a low concentration in the blood.