Tenets of Cell Theory (past - modern)

The Cell Theory

Ø All living things are made of cells.

Ø Cells are the basic units of life.

Ø Cells come only from other cells.

Types of cells:

Ø Prokaryotes - cells with no nucleus or organelles with membranes.
Bacteria and blue-green bacteria are prokaryotic cells.

Ø Eukaryotes - cells that contain a nucleus and organelles surrounded by a membrane.
The cells of protozoa, algae, fungi, plants, and animals are eukaryotic cells.

Classical interpretation of Cell Theory:

1. All organisms are made up of one or more cells.
2. Cells are the fundamental functional and structural unit of life.
3. All cells come from pre-existing cells.
4. The cell is the unit of structure, physiology, and organization in living things.
5. The cell retains a dual existence as a distinct entity and a building block in the construction of organisms.

Modern interpretation

The generally accepted parts of modern cell theory include:

1. The cell is the fundamental unit of structure and function in living things.
2. All cells come from pre-existing cells by division.
3. Energy flow (metabolism and biochemistry) occurs within cells.
4. Cells contain hereditary information (DNA) which is passed from cell to cell during cell division
5. All cells are basically the same in chemical composition.
6. All known living things are made up of cells.
7. Some organisms are unicellular, i.e., made up of only one cell.
8. Others are multicellular, composed of a number of cells.
9. The activity of an organism depends on the total activity of independent cells.