Problem 113 - Objective Biology for NEET

Question

Assertion: \(\mathrm{S}\) and \(\mathrm{Ca}\) are immobile. Reason: \(\mathrm{S}\) and \(\mathrm{Ca}\) are part of the structural component of cell and hence it is not easily released.

Step-by-Step Solution

Answer

The assertion that Sulfur (S) and Calcium (Ca) are immobile is accurate as these elements are integrated into important cellular structures and cannot be easily relocated or removed without causing harm to the cell. The reason given is correct and directly supports the assertion.

Step 1: Analysis of Assertion

Firstly, it is necessary to understand what the term 'immobile' means within this context. Here it relates to the ability of a substance to move or be transported within an organism, specifically within cells. Sulfur and calcium are considered immobile, this means they do not easily move around within the cellular structure once they've been utilized.

Step 2: Analysis of Reason

The reasoning provided explains that S and Ca are a part of the structural component of a cell and hence are not easily released. Biochemically, sulfur is an essential component of certain amino acids and vitamins and is a part of protein structure, while calcium plays a key role in cell signaling and serves as a structural component in bone tissue. Once they've been integrated into these structures, they cannot easily be mobilized.

Step 3: Evaluation of Assertion and Reason

The key point is to evaluate the correlation between the assertion and the reason. Does the fact that S and Ca are part of the structural components of a cell justify their immobility? Yes, as once integrated into cellular structures, removal or relocation of these elements would likely cause damage to the cell, making them effectively immobile within the cellular structure.

Key Concepts

Sulfur Role in Cells

Sulfur is an important element in plant cells, playing various roles crucial for plant health and development. It can be found in amino acids such as cysteine and methionine. These amino acids are building blocks of proteins, necessary for the development and functioning of all living cells. Sulfur also plays a vital role in forming vitamins and co-enzymes, aiding metabolic processes.
Furthermore, sulfur is involved in chlorophyll formation. Chlorophyll is critical for photosynthesis, allowing plants to convert light energy into chemical energy. When sulfur is incorporated into these essential compounds, it becomes a part of the plant's structure. This structural integration is why sulfur is considered immobile; once used in cell structures, it cannot easily be moved elsewhere in the plant.
In summary, sulfur's immobility stems from its role in fundamental cellular components, deeply embedding it within the cellular framework. This is why adequate sulfur nutrition is crucial during the plant's growing period to ensure its availability for incorporation into these essential structures.

Calcium as Structural Component

Calcium, much like sulfur, plays a significant structural role in plant cells. It is identified predominantly as a necessary component of the plant cell wall. Calcium helps in maintaining cell wall stability, providing both rigidity and strength to the plant structure. It's like the 'cement' holding together the bricks that form the plant cell walls.
Additionally, calcium interacts with a protein called pectin. Pectin is found in the middle lamella, the layer between plant cells, where calcium helps form calcium pectate. This compound glues cells together, contributing to the plant's overall integrity.
Beyond providing structural support, calcium is involved in cell division and elongation. It acts as a secondary messenger in cellular signaling pathways. However, once it's a part of these structures, its movement becomes severely restricted. The need for stability in these regions explains calcium's immobility in plants.
Therefore, calcium's immobility necessitates a constant supply from the soil as the plant grows. This ensures that the cells being formed have enough calcium to maintain their proper structural function.

Immobile Nutrients

Some nutrients are classified as immobile within plant cells because, once integrated, they are challenging to relocate or redistribute. This immobility largely impacts how plants manage these nutrients under deficiency conditions.
Sulfur and calcium are key examples of such immobile nutrients. In sulfur's case, its roles in amino acids and vitamins once utilized in proteins make it non-transferable. For calcium, its structural integration in cell walls severely limits its movement after initial deposition.
This characteristic has significant implications for plant nutrition and deficiency management. Immobile nutrients must be provided consistently throughout the growth period of the plant. Since they can't be moved from older tissues to newer growth areas, deficiencies most often show in the newer tissues first, as these newer parts cannot tap into the reserves locked in older tissues.
Therefore, understanding the immobility of these nutrients helps in devising effective strategies for feeding and maintaining healthy plant growth.