Question

How are the simple diffusion and facilitated diffusion similar. And how are they different from each other?

Answer 1

Hint:Simple diffusion is a process in which net movement of the molecules takes place from a region of higher concentration to a region of lower concentration.
But there are certain substances which are lipid insoluble. Also, we know that the plasma membrane of a cell is made up of phospholipids. Therefore, such molecules which are lipid insoluble cannot pass through the phospholipid membrane. Hence, the movement of such substances need to be facilitated. This is done with the help of membrane protein (channel or carrier) which facilitates their movement from high to low concentration. This process is termed as Facilitated diffusion.

Complete answer:
Facilitated diffusion and simple diffusion have some differences and a few similarities between them as discussed below:
Similarities Between the Processes:
$1$. Both the processes are passive processes. It means both of these processes do not require any external source of energy (ATP) for the movement of substances/molecules.
$2.$ in both the processes, the movement of molecules is from a region of high concentration to a region of low concentration. Such a transport is termed as downhill transport.
Differences between the Processes:

SIMPLE DIFFUSION	FACILITATED DIFFUSION
1. The driving force for simple diffusion is the concentration difference across the membrane.	1.The driving force for it is the solute concentration difference across the membrane
2. It is a relatively slow process	2. It is a relatively fast process.
3. Inhibitor molecules have no effect on this process	3. Inhibitor molecules affect this process.
4. In simple diffusion the movement of particles occur along the direction of concentration gradient.	4. In this, movement of molecule can sometimes occur in both the direction
5. It is not solute specific	5. It is solute specific

Note:Often there is confusion regarding facilitated diffusion and active transport. But both these processes are completely different as the former do not require energy, but the later requires energy to occur.