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Cell Theory

Biology (Year 12) - Cells and Composition

Ben Whitten

What are cells?

Cells are the basic structural and functional units of all living organisms. They are the smallest entities that can be considered alive and perform vital functions such as growth, reproduction, and metabolism.

Cells are made up of a complex system of molecules, including proteins, lipids, carbohydrates, and nucleic acids, that work together to sustain the cell's life. They come in different shapes, sizes, and types, each with its own specific functions and abilities.

While all cells share some basic characteristics, such as a cell membrane that regulates the passage of materials in and out of the cell, the specific structure and function of a cell can vary greatly depending on its type and location within an organism.

What is the cell theory?

The cell theory is a fundamental concept in biology that states that all living organisms are composed of one or more cells, that the cell is the basic unit of structure and function in all living things, and that all cells arise from pre-existing cells. The cell theory was first proposed in the mid-19th century by scientists Matthias Schleiden and Theodor Schwann, who observed that all plant and animal tissues were made up of cells.

To summarise, the cell theory states:

  • All organisms are composed of cells

  • All cells come from pre-existing cells

  • The cell is the basic organisational unit of all living things

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