Contrast the processes of facilitated diffusion and active transport (3 marks)

Note that the question is 3 marks. Also note the question uses the word 'contrast' so you must talk about both processes. Cells must communicate with their external environment and vice versa, therefore, substances such as glucose and water must enter and exit cells. However, entry and exit must be regulated, like security regulating entry and exit in concerts and there are different ways of regulation and transport. Since it is a 3 mark question we can do 3 contrasts:
1) Both processes use proteins in the membrane (integral) through which molecules are transported when compared with simple diffusion. Facilitated diffusion uses both channels (water filled proteins through which specific molecules can diffuse) or carrier proteins that alternate between two conformations. Active transport, however, only uses carrier proteins.
2) The second difference between active transport and facilitated transport is the gradient flow. In active transport molecules travel against their concentration gradient (low to high), whereas in facilitated transport it is passive and molecules travel down their concentration gradient (high to low).
3) This leads us to our third contrast. Since substances move against their concentration gradient in active transport, this is a taxing process and energy is required to do so in the form of ATP. Facilitated transport is passive and therefore ATP is not required.