Secondary Active Transport

  • In secondary active transport or coupled transport the energy required is obtained from the transport of sodium into the cell. This transport is down the sodium concentration gradient and as such no direct energy expenditure occurs.
  • On the other hand, to produce the gradient, energy is utilised when sodium is pumped into the extracellular space through the sodium/potassium pump.
  • If the other ion transported in the same time as sodium moves in the same direction of sodium then the transport is called co-transport if in the oppposite direction it is called coutertransport.
  • examples include cotransport of glucose and the countertransport of calcium.