Question

Give one basic difference between osmosis and diffusion.

Answer 1

Osmosis and Diffusion are types of passive transport methods. Both these processes help to transfer molecules in and out of the cell. However, certain basic differences are present with respect to the condition in which these processes take place.

Complete answer:
Passive transport methods transport molecules without any energy. This process works down the concentration gradient, that is the molecules move from a region of higher concentration to a region of lower concentration.
Diffusion is the process by which substances move from a region of their higher concentration to a region of lower concentration to attain equilibrium. For example, if we spray a perfume at a corner of a room, moments later the entire room smells of the perfume. This is because the perfume molecules travelled from the corner of the room to be spread throughout. This process does not require ATP.
Osmosis, on the hand, involves the movement of water molecules specifically. The water molecules move from a lesser concentrated solution to a more concentrated solution through a selectively permeable membrane. This process, like diffusion, is a simple one and does not require ATP.
Therefore, to summarize, the basic difference between diffusion and osmosis is in the nature of molecules transported. Diffusion involves transport of solute molecules, while osmosis involves transport of water molecules through a selectively permeable membrane.

Additional Information: Osmosis and Diffusion are types of passive transport that transports molecules to attain equilibrium. Diffusion takes place in all the three forms of matter, that is solid, liquid and gases and occurs in all directions. Whereas, osmosis takes place in only liquid form of matter and the movement is one directional.
Another type of diffusion called Facilitated diffusion exists where molecules are transported with the help of protein across the cell membrane. This process requires ATP as the driving force.
Osmotic solution can be of three types based on the tonicity of the solution. They are Hypotonic, Isotonic or Hypertonic. For Hypotonic solutions, the movement of water molecules is from outside to inside the cell owing to lower concentration of water inside. For Isotonic solutions, the net movement of water molecules is the same since the concentration of liquid is the same on both sides. On the other hand, hypertonic solutions are more concentrated than the cells. Therefore, water moves out of the cell, if placed in hypertonic solutions.

Note: Diffusion and Osmosis are modes of passive transport where molecules are transported. Both the processes take place without the requirement of energy expenditure. The basic difference between these processes are in the nature of molecules they transport.