PinkMonkey Online Study Guide-Biology
3.1 Modern cell theory
Modern biologists have made certain additions to the original cell theory which now states that:
1. All organisms are made up of cells.
2. New cells are always produced from pre-existing cells.
3. The cell is a structural and functional unit of all living things.
4.The cell contains hereditary information which is passed on from cell to cell during cell division.
5. All cells are basically the same
in chemical composition and metabolic activities.
As the cells of different parts of an organism (such
as epithelial cell, muscle cell, nerve cell, etc). vary in shape, size
and internal structure, no cell can be described as a typical one. In
spite of all these variations, they are all cells, showing certain common
Figure 3.2 Plant cell