Question

Stationary phase occurs due to (a) Increase in distance (b) Limited nutrient supply (c) Thickening of cell wall (d) None of these

Short answer

The correct answer is (b) Limited nutrient supply.

Step-by-step solution

Understanding the Stationary Phase

The stationary phase in the life of a cell or an organism is when the rate of cell growth equals the rate of cell death. This phase is caused by a limitation in an essential nutrient.

Analyze the Options

An increase in distance or thickening of the cell wall would not necessarily lead to a stationary phase. Thus, options (a) and (c) can be eliminated.

Identify the Correct Option

Given the understanding of the stationary phase and the provided options, option (b) Limited nutrient supply, is the correct answer.

Key concepts

Cell Growth

The concept of cell growth is essential to understanding biological processes. Cell growth refers to the increase in cell size and the number of cells. This can be due to factors such as the availability of nutrients and energy sources. It occurs during the "log phase," where cells rapidly divide, provided the conditions are ideal.

During this phase, the cells are highly active metabolically, using nutrients to build proteins and other essential components. As the cell size increases, the cell prepares to divide by duplicating its DNA, and then it divides to form two daughter cells.

• Cell growth is controlled by the availability of resources.
• Temperature, pH, and nutrient concentrations affect growth rates.
• In laboratories, growth media often provide the necessary nutrients for cell culture.

Understanding cell growth helps explain how organisms develop, replicate, and sustain life. In nature, growth can be limited by the surrounding environment, leading to various growth phases.

Cell Death

Cell death is a natural part of the life cycle of cells, acting as a regulator to maintain balance in a population. This process can occur due to two primary mechanisms: necrosis and apoptosis.

**Necrosis** is an uncontrolled process that typically results from injury or severe stress, causing cell membranes to burst and leak contents into the surrounding tissue. This can lead to inflammation or damage to neighboring cells.

**Apoptosis**, on the other hand, is a programmed cell death. It is a controlled process where cells self-destruct for the greater good of the organism, playing important roles in development and disease prevention.

• Cell death balances cell growth during the stationary phase.
• In multicellular organisms, apoptosis removes unnecessary or damaged cells.
• The balance of growth and death is essential for organism health.

In the context of the stationary phase, cell death increases when nutrients are scarce, helping to stabilize the population by matching the rate of cell growth.

Nutrient Limitation

Nutrient limitation is a crucial factor affecting cell growth and can trigger a stationary phase in cell cultures. As cells grow, they consume nutrients from their environment. When external supplies dwindle, growth slows, and this leads to the plateau of the stationary phase.

Typically, limitations in key nutrients such as nitrogen, carbon, or phosphorous can stunt growth rates. Cells must adapt to low-resource environments by adjusting their metabolism.

• Nutrient depletion is more pronounced in closed systems without new inputs.
• During scarcity, cells conserve resources and reduce metabolic activity.
• Some cells enter a dormant state to survive extended periods of shortage.

Understanding how nutrient limitations impact cell growth allows scientists and researchers to better manage biotechnological processes, ensuring optimal growth and productivity in lab settings.