co transport ( crying inside )

• The role of the ileum is to absorb the molecules produced by digestion , e. glucose
• Glucose is absorbed from the lumen ( cavity ) of the ileum.
• Glucose molecules move from epithelial cells into blood stream
• Glucose molecules use facilitated diffusion to diffuse into the epithelial cells lining the ileum , then they go into the bloodstream
• The rate of facilitated diffusion depends on the size of concentration gradient
• Concentration gradient falls as glucose diffuses into the epithelial cells meaning facilitated diffusion cannot absorb all of the available glucose
• Glucose in the ileum is absorbed through facilitated transport and co-transport
• Co transport stage 1)

  Carrier protein called sodium-potassium pump uses ATP to actively transport sodium ions out of epithelial cells into the blood stream

  At the same time it also does this to potassium atoms into the epithelial cells
• Co transport stage 2)

  Sodium-glucose co-transporter diffuses sodium ions into epithelial cell.

  It also actively transports glucose molecules into the cell

  
  

  ensures glucose is absorbed at a fast rate
• Epithelial cells contain a large number of mitochondria, this provides enough ATP for sodium-potassium pump
• The membrane of epithelial cells is folded into large number of microvili , increasing the surface area , providing more space for membrane proteins
• There is a steep concentration gradient between epithelial cells and the blood as glucose molecules are rapidly carried away