Problem 140 - Objective Biology for NEET

Question

Unloading of mineral occurs at the fine vein endings through (a) Diffusion (b) Active uptake (c) Both (a) and (b) (d) None of these

Step-by-Step Solution

Answer

The unloading of mineral at the fine vein endings takes place through both Diffusion and Active Uptake.

Step 1: Understanding the Concepts

Minerals are primarily transported in plants using two mechanisms: diffusion and active uptake. Diffusion is the movement of molecules from a region of high concentration to a region of low concentration. Active uptake, on the other hand, is the process in which cells expend energy to transport molecules against the concentration gradient, from a region of low concentration to a region of high concentration.

Step 2: Identifying the Correct Choice

Given both methods are applicable for the transport of minerals in plants, the unloading at the fine vein endings can take place by either diffusion (option (a)) or active uptake (option (b)). Hence, the correct answer is both (a) and (b), i.e., option (c).

Key Concepts

Diffusion

Diffusion is a passive process that plays a crucial role in the transportation of minerals in plants. It allows the movement of molecules from areas where they are in higher concentration to areas where they are in lower concentration. This natural process occurs without the expenditure of energy. It relies on the inherent kinetic energy of molecules and the concentration gradient that exists within the plant tissues.

In plants, diffusion helps in the movement of minerals such as potassium and nitrate from the soil into the roots and further into other parts of the plant. This movement is essential for various physiological functions and cellular activities.

• Diffusion is efficient for small molecules and over short distances.
• It tends to occur across cell membranes which are selectively permeable.

For effective diffusion to occur, the difference in concentration (or concentration gradient) must be significant enough to drive the movement of these molecules naturally.

Active Uptake

While diffusion facilitates the passive transport of minerals, active uptake is also critical for plant survival, particularly when dealing with essential nutrients that are present in low concentrations in the soil. Active uptake involves the transport of molecules from an area of lower concentration to an area of higher concentration, which is against the concentration gradient. This process requires energy, often derived from ATP, making it an active process.

Active uptake is crucial for the absorption of minerals such as phosphate and iron, which might not be sufficiently available through diffusion. It ensures that plants can acquire all necessary nutrients, even in suboptimal conditions, by using specific proteins embedded in the cell membranes.

• Energy-dependent mechanism that uses transport proteins.
• Essential for nutrient uptake when concentrations in the soil are low.

Without active uptake, plants would struggle to get the essential nutrients required for their growth, especially in nutrient-deficient soils.

Concentration Gradient

The concentration gradient is a fundamental concept when discussing both diffusion and active uptake. It refers to the difference in concentration of a substance between two regions. In the context of plant mineral transport, this gradient determines the direction and method by which nutrients move within the plant.

For diffusion, the concentration gradient is the driving force that pushes molecules from an area of high concentration to an area of low concentration, allowing nutrients to spread efficiently without energy use. Conversely, in active uptake, the plant must work against the concentration gradient, requiring energy to move nutrients into areas of higher concentration.

• Concentration gradients result in different transport mechanisms.
• They are vital for maintaining cellular homeostasis.

Understanding concentration gradients is key to grasping how plants regulate the internal balance of minerals, which is essential for maintaining cellular processes and overall plant health.