co transport and active transport

• Active transport


  Movement of substances from an area of low concentration to an area of higher concentration, requiring energy in the form of ATP and carrier proteins
• Co-transport


  A type of active transport where two different molecules are transported together across a membrane
• Active transport process


  1. Carrier protein attaches to molecule

  2. ATP binds to carrier protein and is hydrolyzed

  3. Carrier protein changes shape

  4. Molecule is released on the other side

  5. Phosphate is released, restoring carrier protein to original shape
• Co-transport of glucose and sodium ions occurs in the ileum of the small intestine
• Co-transport of glucose and sodium in the ileum

  1. Sodium ions actively transported from epithelial cell into blood

  2. Sodium ion concentration gradient allows sodium to diffuse into epithelial cell

  3. Sodium-glucose co-transporter protein binds sodium and glucose, transporting them together into epithelial cell

  4. Glucose then diffuses down concentration gradient from epithelial cell into blood
• Microvilli


  • Increase surface area of epithelial cells, allowing more co-transporter proteins to be embedded in the membrane
• More co-transporter proteins


  Increased absorption of glucose and amino acids
• Active transport and co-transport are ways to move molecules across a membrane
• Co-transport is a type of active transport that always involves ATP
• Active transport requires carrier proteins and the hydrolysis of ATP to cause a shape change that releases molecules