Problem 153 - Objective Biology for NEET

Question

Assertion: Imbibition is also diffusion. Reason: The movement of water in the above process is along a concentration gradient.

Step-by-Step Solution

Answer

The assertion 'Imbibition is also diffusion' is partially correct as imbibition is a form of diffusion, but not equivalent to diffusion. The reason 'The movement of water in the above process is along a concentration gradient' is true.

Step 1: Understand Imbibition

Imbibition is a special type of diffusion where water is absorbed by solids-colloids causing an enormous increase in volume. Examples of imbibition include the absorption of water by seeds and dry wood. Therefore, Imbibition is a form of diffusion, but not all forms of diffusion are imbibition.

Step 2: Understand Diffusion and Concentration Gradient

Diffusion is the process of movement of molecules from an area of high concentration to an area of lower concentration. The term concentration gradient refers to this particular direction of movement. This principle is universal and applies to all molecules, including water. Water molecules move from an area where water is in high concentration (or the solute is in low concentration) to an area where the water concentration is less (or the solute is in high concentration).

Step 3: Evaluate the Assertion and the Reason

Given this understanding, we can now evaluate the reason and the assertion. It is correct to say that the movement of water in imbibition is along a concentration gradient, so the reason is true. However, though imbibition is a type of diffusion, they are not equivalent. Thus, the assertion, 'Imbibition is also diffusion', though partially true, is not entirely accurate. Therefore, the assertion is partially correct, but not totally.

Key Concepts

Diffusion

Diffusion is a fascinating and fundamental process that occurs in nature. It's the movement of particles from areas of higher concentration to areas of lower concentration until they are evenly distributed. This movement is driven by the natural tendency of particles to spread out and fill the available space. For example, if you drop a sugar cube into tea, the gradual sweetening of the entire cup is due to diffusion.
Diffusion is crucial because it helps maintain balance in different environments and plays a role in various biological and physical processes. It occurs not just with liquids, but also gases like oxygen and carbon dioxide, which diffuse across cell membranes in our body.

Concentration Gradient

A concentration gradient is an aspect closely related to diffusion. It refers to the variation in the concentration of particles within a given space. Imagine a room with perfume sprayed in one corner. The perfume molecules are initially concentrated in one area and diffuse across the room because of the concentration gradient.
The flow of particles is always directed from an area with higher concentration to one with lower concentration, similar to a downhill movement. This difference is what drives diffusion and is key to many physiological processes, including nutrient absorption in cells.

Water Absorption

Water absorption is a process wherein water molecules are taken up by materials, which can lead to significant changes. A good example of water absorption is a sponge soaking up water. In biological terms, plants absorb water through their roots, which is vital for their survival.
This absorption can occur in response to a concentration gradient. For instance, when seeds absorb water, it allows them to swell and start the germination process. Understanding water absorption helps explain critical processes such as nutrient uptake and the structural changes in materials.

Colloids

Colloids play a surprising role in many everyday processes. They are mixtures where one substance is dispersely distributed within another without dissolving, like jelly or fog. In water absorption, colloidal particles such as proteins in seeds help in imbibition, as they attract and hold water.
These particles can swell and facilitate the immense volume change seen during imbibition. Colloids maintain their dispersion over time, preventing settling, which is why they can consistently absorb water. This understanding of their properties and functions helps explain significant phenomena in both nature and industrial applications.