Question

What are the differences and similarities between diffusion, facilitated diffusion, osmosis and active transport?

Answer 1

Hint: The passage of substances through the cell membrane, either into or out of the cell, is referred to as cell transport. Stuff may often only pass through the phospholipid bilayer. Other times, a protein, such as a channel protein or another transmembrane protein, is required to help substances cross the cell membrane.

Complete answer:
The Plasma membrane is an important covering of the cell which allows the passage of molecules in and out of the cell. It is semi-permeable which allows only selective molecules to pass through it. The movement of molecules across the membrane takes place by diffusion, facilitated diffusion, osmosis and active transport.
Let us discuss the similarities and differences between diffusion, facilitated diffusion, osmosis and active transport in the table below.

	Diffusion	Facilitated Diffusion	Osmosis	Active transport
Definition	Diffusion is described as the transfer of molecules from a high-concentration area to a low-concentration area.	Facilitated diffusion is the passage of molecules across a cell membrane from a high-concentration area to a low-concentration area with the help of carrier molecules	Osmosis is the movement of solvent molecules from the region of higher concentration to the lower concentration across the semi-permeable membrane.	The movement of materials against a concentration gradient is known as active transport (from a region of low concentration to a region of high concentration).
Example	Eg- Diffusion of gases through the stomata.	Eg-Movement of ions across the plasma membrane	Eg- Movement of water across the plasma membrane	Eg- ATP hydrolysis.
Energy Requirement	No	No	No	Yes, in the form of ATP
Semi-Permeable membrane	Not required	Not required	required	Not required.
Concentration gradient	Moves with respect to concentration gradient.	Moves with respect to the concentration gradient.	Moves with respect to concentration gradient.	Moves against the concentration gradient
Movement of substances	Gases, liquid	Ions, glucose, polar molecules	water	Many molecules.

Note: The sodium-potassium pump is the most well-known example of a primary active transport protein. The ion gradient that causes neurons to fire is created by this pump. The water is absorbed by the roots from the soil by the process of osmosis. The exchange of gases in the cell takes place by the process of diffusion.