Question

Diffusion pressure is directly proportional to:
A. Concentration of molecules diffusing
B. Kinetic energy of diffusing molecule
C. Concentration gradient
D. All of the above

Answer 1

Hint: The plants undergo transportation of nutrients and water without having blood vessels like humans. It is because the plants undergo a diffusion process to carry out the movement of ions and water molecules through the cells.

Complete Answer:
To solve this question, we have to know about the diffusion pressure. It is the hypothesis given by Meyer in 1938. This hypothesis indicates the potential ability of ions and molecules of the substances to diffuse from higher concentrated regions to the lower concentrated region. The diffusion pressure is affected by increase in the temperature, the increase in temperature results in the increase in the kinetic energy of the substance and in increases the rate of diffusion.

The diffusion pressure is also affected by the concentration gradient, the high concentration gradient resulting in the increase in the diffusion rate. The water tendency to move was used to be measured in terms of diffusion pressure; the pure solvent considered having the maximum diffusion pressure, if solute is added to the pure solvent the diffusion pressure decreases this is considered as suction pressure.

There are three types of diffusion; simple diffusion, osmosis, and facilitated diffusion.
(I) In simple diffusion, the molecules or the ions diffuse down the concentration gradient that means it moves to the lower concentration region to higher concentration region for example; exchange of gases during photosynthesis.
(II) In osmosis, the water molecules move from the low concentration region to the high concentration region through a semipermeable membrane.
(III) In facilitated diffusion, the ions and water molecules move through the plasma membrane and the diffusion is facilitated by transport or carrier proteins.

So, the diffusion pressure is directly proportional to the concentration of molecules diffusing. The kinetic energy gets changed after the diffusion takes place and this also leads to the change in the concentration gradient.

Thus, the correct option is ‘A’. Concentration of molecules diffusing.

Note: The diffusion pressure inside the cell gets stopped when the substance or ion concentration become equal in both regions. This does not mean the molecules of the substance stop its movement; it 's just that the overall movement in any direction gets stopped.