Summary
States that all living things are made of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.
In depth
Developed in the 1830s by Schleiden and Schwann and extended by Virchow's 1855 claim that every cell comes from a cell, the theory unified biology. It has three pillars: all organisms consist of one or more cells; the cell is the smallest unit that shows all the properties of life (metabolism, growth, response, reproduction); and cells only arise by division of existing cells.
Modern additions say cells carry hereditary information as DNA, that they are chemically similar across species, and that energy flow occurs within cells. Viruses are a classic edge case because they are not cellular and cannot reproduce on their own.
Frequently asked questions
What is Cell Theory?
States that all living things are made of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.
Which area of biology covers Cell Theory, and how advanced is it?
Cell Theory is one of the 52 topics in Cell Biology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Telomeres and Senescence, Active Transport, Mitosis.
Why does Cell Theory matter?
It rules out spontaneous generation and justifies using single cells such as E. coli or yeast as models for all life.
What should I learn before Cell Theory?
Cell Theory is a Beginner topic, so no earlier topic is required. Other Beginner topics in Cell Biology that pair well with it include Prokaryotic Cell, Eukaryotic Cell, Plasma Membrane.
What topics are related to Cell Theory?
The closest topics to Cell Theory are Telomeres and Senescence, Active Transport, Mitosis, Cell Signalling. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Cell Theory?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Cell Theory. To practise the whole of Cell Biology, use the Cell Biology quiz.
How is Cell Theory different from Telomeres and Senescence?
Cell Theory: States that all living things are made of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells. Telomeres and Senescence: Shortening of chromosome end caps with each division eventually triggers permanent growth arrest called senescence. Read both side by side and note what each one explains.
How should I study Cell Theory step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Telomeres and Senescence and explain the difference aloud. Finally, take the Cell Biology quiz and come back to this page for any question you miss.