3.3 active transport

• active transport - movement of particles from a region of low concentration to a region of high concentration (against concentration gradient)
• protein carriers are required for active transport
• proteins are specifically shaped to fit the ion (can only transport certain molecules)
• the protein changes shape to release the ion on the other side of the membrane
• ex: uptake of glucose (i)

  by epithelial cells in the villi of the small intestine
• ex: uptake of glucose (ii)

  by kidney tubules in the nephron
• ex: uptake of ions from soil water by root hair cells in plants
• active transport of ions into the root hair cell:

  • lowers the water potential
• active transport of ions into the root hair cell:

  • increases osmosis into the cell