Cell is the basic unit of life. Discuss in brief.

Cells are capable of independent existence in unicellular organisms like Amoeba and Paramecium. In multicellular organisms, cells are specialized to perform specific functions but still retain the basic life processes.

The cell theory, proposed by Schleiden and Schwann and later modified by Virchow, states that:

• All living organisms are composed of cells.

• The cell is the structural and functional unit of life.

• All cells arise from pre-existing cells (Omnis cellula e cellula).

Cells vary in shape, size, and structure according to the function they perform. For example:

• Nerve cells are long and branched for transmitting signals.

• Red blood cells are biconcave to carry oxygen efficiently.

Each cell has basic components such as:

• Plasma membrane: regulates entry and exit of substances.

• Cytoplasm: site of metabolic activities.

• Nucleus: controls cellular activities and contains genetic material.

In multicellular organisms, cells are organized into tissues, tissues into organs, and organs into systems. However, the cell remains the fundamental unit at each level.

Hence, whether an organism is made of a single cell or trillions of cells, the basic processes of life occur at the cellular level, making the cell the foundational unit of life.