Cell: The Unit of Life

Cell Theory

Formulated by Schleiden, Schwann, and later modified by Rudolf Virchow, it states that all living organisms are composed of cells and products of cells, and all cells arise from pre-existing cells (Omnis cellula e cellula).

Prokaryotic vs Eukaryotic Cells

Prokaryotic cells lack a true membrane-bound nucleus and distinct membrane-bound organelles (e.g., bacteria), whereas eukaryotic cells possess a well-organized nucleus and complex membrane-bound organelles (e.g., plant and animal cells).

Fluid Mosaic Model

Proposed by Singer and Nicolson, this model describes the plasma membrane as a quasi-fluid phospholipid bilayer with embedded and peripheral proteins that allow lateral movement of molecules.

Endomembrane System

A coordinated network of membranous organelles—including the endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles—whose functions are coordinated for protein synthesis, lipid transport, and cellular digestion.

Mitochondria and Plastids

Mitochondria are the 'powerhouses of the cell' responsible for aerobic respiration and ATP production, while plastids (like chloroplasts) are plant-specific organelles involved in photosynthesis and pigment storage.