In short
A cell is the basic structural and functional unit of life. Every living thing is made of one or more cells, and every cell comes from an existing cell.
Cell theory says three things: all organisms are made of cells, the cell is the unit of structure and function, and new cells come from existing cells. Cells are mostly to across, so a microscope is needed to see them. A prokaryotic cell, such as a bacterium, has no nucleus. A eukaryotic cell, in plants, animals, fungi and protists, has a nucleus and other membrane-bound organelles.
A human body is made of about cells. A bacterium such as E. coli is a single cell about long. A dog, like any animal, is made of cells.
Also searched as: is a dog made of cells, cell theory.
Pick your exam to see its syllabus, where you stand in each unit and what to practise next.
See exam preparation