Ch 8Cell: The Unit of Life — Class 11 Biology, concept-first.

Every living organism, whether a single free-floating bacterium or a multi-tonne blue whale, is built from the same basic unit of construction: the cell.

Cell Theory is one of the unifying principles of biology, and like most great scientific ideas it was not the work of a single person but was built up gradually through the observations of several sci…

All cellular life on Earth is organised according to one of two fundamentally different structural plans -- the prokaryotic plan and the eukaryotic plan -- and this distinction is the single most impo…

A generalised prokaryotic cell, though structurally far simpler than a eukaryotic cell, is not a formless blob -- it has a definite, genetically determined shape, maintained largely by its cell wall,…

The outer boundary of a typical bacterial cell is not a single simple layer but a chemically complex structure made up of three distinct layers working together as a single protective and functional u…

Plant cells and animal cells are both eukaryotic, and so they share the fundamental architecture common to all eukaryotic cells: a true, membrane-bound nucleus, and a common set of membrane-bound orga…

Every cell, whether prokaryotic or eukaryotic, is bounded by a plasma membrane (also called the cell membrane) -- the thin, selectively permeable barrier that separates the living interior of the cell…

Unlike the plasma membrane, which is a living, dynamic structure common to every cell, the cell wall is a non-living, rigid structure found only in plant cells (and, in a chemically different form, in…

The cytoplasm of a eukaryotic cell contains a group of organelles -- the endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles -- that are grouped together and studied as a single functi…

The endoplasmic reticulum (ER) is an extensive, interconnected network of membrane-bound tubules, vesicles and flattened sacs called cisternae that extends throughout the cytoplasm of a eukaryotic cel…

Lysosomes are small, membrane-bound vesicular organelles, first described by the Belgian cytologist Christian de Duve, that are formed by the packaging activity of the Golgi apparatus.

Mitochondria are among the most important organelles in a eukaryotic cell, popularly and accurately described as the "powerhouse of the cell" because they are the principal site at which aerobic respi…

Ribosomes are small, non-membrane-bound particles composed of ribonucleoprotein -- a combination of ribosomal RNA (rRNA) and protein -- and they are, without exception, the sites within any cell where…

Microbodies are a further category of small, membrane-bound organelles found scattered through the cytoplasm of both plant and animal cells.

Cilia and flagella are specialised, hair-like or whip-like extensions of the cell surface, found projecting outward from the plasma membrane of many eukaryotic cells, and both are chiefly associated w…

This chapter examined the cell as the fundamental structural and functional unit of every living organism, beginning with its historical discovery by Robert Hooke in 1665 and building up, through the…