Movement of Water due to DPD MCQ - Practice Questions with Answers

• Recall: Diffusion can be defined as the movement of particles or ions or molecules of a substance from a region of its higher concentration to the region of its lower concentration.
• Recall: Pure water has the maximum diffusion pressure of 1236 atm.
• When a solute is dissolved in pure water, the number of free water molecules is reduced and the pressure with which pure water could diffuse earlier is now reduced.
• Hence, the solution has a lower diffusion pressure as compared to the pure solvent.
• If the addition of the solute is continued, the diffusion pressure will be further lowered. 
• Therefore, the value by which the diffusion pressure of a solution is lower than that of a pure solvent is called diffusion pressure deficit.
• The solution has a high deficit of diffusion pressure, so water moves from low DPD region to high DPD region.
• DPD = Diffusion pressure of pure water - Diffusion Pressure of water in the solution
• Because of the presence of diffusion pressure deficit, a solution will always tend to make up the deficit by absorbing water. 
• Hence, the diffusion pressure deficit is the water-absorbing capacity of a solution.
• Therefore, DPD can also be called suction pressure (SP).
• It is the difference between osmotic pressure and turgor pressure.
• DPD = OP - TP
• DPD of a completely plasmolysed cell: In a plasmolysed cell, TP = 0. And OP is maximum. So, DPD = OP
• DPD of a fully turgid cell: In a turgid cell, TP = OP. So, DPD is zero.

Cell to Cell Movement of Water:

• The movement of water from one to the other is dependent on the DPD.
• Water moves from low DPD to high DPD.