Chapter 5 · Biology
Cell: Chapter Introduction
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You began as a single cell. Every living thing is built of cells: how they were discovered, what is inside, how they divide, and the cell theory.
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Discovery of the CellIn 1665 a thin slice of cork showed tiny boxes Robert Hooke called cells. Then came living cells (1674) and the nucleus (1831).Biology
Key points
- Every human begins as one cell; an adult body has trillions of cells.
- All living things are made of cells; an amoeba or a bacterium is a single cell.
- Robert Hooke (1665) saw tiny box-like compartments in thin cork slices and named them cells.
- A cell has a cell membrane, a nucleus and organelles such as mitochondria; it makes new cells by division (1 → 2 → 4 ...).
Cell theory
- All living things are made of one or more cells.
- The cell is the basic structural and functional unit of life.
- New cells arise only from pre-existing cells (by division).
Inside a cell
| Part | Job |
|---|---|
| Cell membrane | Outer boundary; lets some substances in and out (selectively permeable) |
| Nucleus | Holds the genetic material; controls the cell |
| Mitochondria | Release energy from food |
| Endoplasmic reticulum, vesicles | Make and carry materials inside the cell |
What this chapter covers
- Discovery: Hooke, Leeuwenhoek, better microscopes
- Structure: membrane, cell wall, nucleus, cytoplasm
- Organelles and their jobs
- Cell division
- Cell theory
Quick quiz
3 questions. Choose an answer for each, then submit to see your score and the explanations.
More from The Fundamental Unit of Life
Robert Hooke and the Discovery of CellsThe man who named the cell left no surviving portrait. Meet Robert Hooke, his book Micrographia, his lamp-lit microscope and his count of cork cells.Biology
Cell TheoryYour body has about 37 trillion cells. Three scientists showed that every living thing is built from cells, and every cell comes from another cell.Biology
Unicellular and Multicellular OrganismsAn amoeba is one cell; you are about 37 trillion. In one, a single cell does everything; in the other, cells share the work.Biology