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Chapter 3: Cell Structure and Organization

Study the first subtopic below. Unlock types of cells, animal & plant cells, differentiation, specialised cells and assessment in the app.

1. Key Terms and Concepts

Cell — The basic structural and functional unit of all living organisms.

Cell theory — The scientific theory that states all living things are made of cells, cells are the basic unit of life, and all cells arise from pre-existing cells.

Prokaryotic cell — A simple cell that lacks a membrane-bound nucleus and membrane-bound organelles (e.g. bacteria).

Eukaryotic cell — A complex cell that has a true membrane-bound nucleus and membrane-bound organelles (e.g. plant and animal cells).

Organelle — A specialized structure within a cell that performs a specific function.

Cell membrane — The thin, flexible, semi-permeable outer boundary of the cell that controls movement of substances in and out.

Cytoplasm — The jelly-like substance that fills the cell and is the site of many chemical reactions.

Nucleus — The control centre of the cell that contains genetic material (DNA).

Cell differentiation — The process by which cells become specialized to perform particular functions.

Tissue — A group of similar cells working together to perform the same function.

Organ — A structure made of different tissues working together to perform a specific function.

Organ system — A group of organs that work together to carry out a major body function.

2. The Cell (Free full subtopic)

Discovery of the Cell

In 1665, English scientist Robert Hooke designed an improved microscope.
He examined thin slices of cork (from tree bark) and observed many box-like compartments packed together like a honeycomb.
He named these units cells (from the Latin word for “small rooms”).
All living things are made up of cells. Life processes (nutrition, respiration, excretion, etc.) take place inside cells.
Therefore, cells are the basic functional units of life.

The Cell Theory

Observations by Hooke and later scientists led to the development of the cell theory. The main points are:

All living things are composed of cells.
Cells are the basic unit of structure and function of living things.
All cells are produced from pre-existing cells.
Cells contain inherited information (DNA) that controls their activities.
All cells are basically similar in chemical composition.
All life processes take place inside cells.

The cell theory applies to every living organism, whether microscopic or large.

Spotlight

Robert Hooke’s cork cells were actually the empty cell walls of dead plant cells. The living contents had already dried up. Later, Anton van Leeuwenhoek used better lenses to observe living cells such as bacteria and blood cells for the first time.

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3. Types of Cells (prokaryotic vs eukaryotic)
4. Animal and Plant Cells (structure, organelles, differences)
5. Cell Differentiation and Organisation (tissue → organ → system)
6. Specialised Cells (RBC, WBC, sperm, root hair, guard cells, xylem, palisade)
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