Cell Biology: Discoveries, Theory, and Cell Types
Key Discoveries in Cell Biology
Robert Brown’s Contribution
What was the contribution of Robert Brown?
He discovered the cell nucleus through his studies of plant cells by staining the cells.
Johannes Purkinje’s Contribution
What was the contribution of Johannes Purkinje?
He identified the viscous substance (protoplasm) within cells where cell components could move.
The Cell Theory
Scientists Who Established the Cell Theory
- Scheiden Mathias (botanist): All plants are composed of plant cells.
- Schwann Theodor (zoologist): All animals are composed of cells.
Principles of Cell Theory
- All living organisms are made up of one or more cells, from the smallest bacterium to the largest multicellular organism.
- The cell is the basic unit of organization of life; it is the structure in which all the chemical reactions necessary for life occur.
- All cells arise from pre-existing cells through the process of mitosis, as discovered by pathologist Robert Virchow.
Understanding the Cell
What is a Cell?
A cell is considered the basic vital, anatomical, physiological, and genetic unit of all living organisms.
Why are These Qualities Attributed to the Cell?
- Vital: It is the single smallest living entity.
- Anatomical: Every living being is composed of at least one cell.
- Physiologic: Cells possess all the physiological and chemical mechanisms to stay alive.
- Genetic: Every cell originates from another existing cell.
Branches of Biology Studying the Cell
- Cytology: Organization and functioning of cells.
- Biochemistry: Chemical reactions within cells.
- Physiology: Study of cell functions.
- Biophysics: Physical phenomena inside the cell.
- Genetics: Study of the transmission of hereditary characters within the cell.
Cellular Activity
What is the activity of an organism?
The activity of an organism is the result of the coordinated activity of many cells working together to perform complex tasks such as digestion.
Microscope Development
First Microscope
Who created the first microscope?
Zacharias Janssen, a Dutch lens manufacturer, in 1591.
First Transmission Electron Microscope
Who created the first transmission electron microscope?
Ernst Ruska in 1931.
First Scanning Electron Microscope
Who created the first scanning electron microscope?
Von Ardenne in 1934.
Types of Cells
Two Main Types of Cells
- Prokaryote:
- Do not have a defined nucleus (e.g., bacteria).
- Are almost always unicellular organisms.
- Often form colonies.
- Eukaryote:
- Have a nucleus (e.g., mammals).
- Organisms formed by these cells are multicellular.
- May form colonies where the body is poorly developed or well-developed.
What are Colonies?
Cellular aggregates maintain their independence if separated; physiological groups are linked together by a structure called Plasmodesma.
Eukaryotic Cell Structure
Structures of a Eukaryotic Cell
- Nucleus: Stores genetic information (DNA and RNA) that directs cell activities.
- Cytoplasm: The substance inside the cell, rich in water, salts, and other molecules.
- Cell Membrane: The structure that constitutes the outer limit of the cell and separates it from its environment.