General Biology 1: The Cell Theory

Study Notes

Cells are the fundamental structural unit of all living organisms.
The cell is too small to be seen by the naked eye, generally around five micrometers.
Contains genetic information determining traits such as eye color, blood type, and sex.

Zacharias Janssen (1590): Invented the first compound microscope, enhancing resolution with multiple lenses for 2D images.
Robert Hooke (1665): Used a light microscope to observe cork, coining the term "cell" for the tiny chambers he saw. His findings were published in 'Micrographia'.
Anton Van Leeuwenhoek (1673): First to use a microscope to study living microorganisms, referring to them as "animalcules." Also observed bacteria, marking a discovery of free-living cells.
Robert Brown (1831): Discovered the nucleus within a cell.
Felix Dujardin (1834): Identified the semi-fluid substance within cells, originally naming it "sarcode."
Matthias Schleiden (1838): Concluded that all plants are composed of cells, collaborating to develop early principles of cell theory.
Theodore Schwann (1839): Stated that all animals are made up of cells, working alongside Schleiden on cell theory.
Jan Evangelista Purkinje (1840): Renamed "sarcode" to "protoplasm," referring to the first living substance in cells.
Rudolph Virchow (1855): Established that cells arise from pre-existing cells, contributing the third tenet of cell theory. Coined the phrase "Omnis Cellula e Cellula," emphasizing cellular reproduction.

Postulates that all living organisms consist of cells, which are the basic unit of life.
All cells arise from pre-existing living cells, consolidating foundational principles of biology.

Important figures:
- Schleiden: All plants are made of cells.
- Schwann: All animals are made of cells.
- Virchow: All cells come from pre-existing cells.
Remember the contributions of Hooke, Leeuwenhoek, Virchow, and Schwann in forming the Cell Theory.

Cell Membrane:
- Composed of a flexible bilayer of proteins and lipids.
- Functions to separate the interior of the cell from the external environment and is selectively permeable.
Cell Wall:
- A rigid layer found in plants, fungi, and some bacteria that provides support and protection.

All living organisms are composed of cells.
Cells are the basic unit of life.
Modern cell theory emphasizes that all cells come from pre-existing cells, underscoring the continuity of life at the cellular level.