Ch 7: VOCABULARIES:
(1) nucleolus
(2) nucleus
(3) ribosome
(4) vesicle
(5) rough endoplasmic reticulum (ER)
(6) Golgi apparatus
(7) Cytoskeleton
(8) smooth endoplasmic reticulum
(9) mitochondria
(10) vacuole
(11) cytoplasm
(12) lysosome
(13) centrioles within centrosome
(1) nucleolus
(2) nucleus
(3) ribosome
(4) vesicle
(5) rough endoplasmic reticulum (ER)
(6) Golgi apparatus
(7) Cytoskeleton
(8) smooth endoplasmic reticulum
(9) mitochondria
(10) vacuole
(11) cytoplasm
(12) lysosome
(13) centrioles within centrosome
To find help on definitions, click on bar.
The CELL THEORY, or cell doctrine, states that all organisms are composed of similar units of organization, called CELLS. The concept was formally articulated in 1839 by Schleiden & Schwann and has remained as the foundation of modern biology. The idea predates other great paradigms of biology including Darwin's theory of evolution (1859), Mendel's laws of inheritance (1865), and the establishment of comparative biochemistry (1940).
Formulation of the Cell Theory
In 1838, Theodor Schwann and Matthias Schleiden were enjoying after-dinner coffee and talking about their studies on cells. It has been suggested that when Schwann heard Schleiden describe plant cells with nuclei, he was struck by the similarity of these plant cells to cells he had observed in animal tissues. The two scientists went immediately to Schwann's lab to look at his slides. Schwann published his book on animal and plant cells (Schwann 1839) the next year, a treatise devoid of acknowledgments of anyone else's contribution, including that of Schleiden (1838). He summarized his observations into three conclusions about cells:
1) The cell is the unit of structure, physiology, and organization in living things.
2) The cell retains a dual existence as a distinct entity and a building block in the
construction of organisms.
3) Cells form by free-cell formation, similar to the formation of crystals (spontaneous generation).
We know today that the first two tenets are correct, but the third is clearly wrong. The correct interpretation of cell formation by division was finally promoted by others and formally enunciated in Rudolph Virchow's powerful dictum, "Omnis cellula e cellula"...
"All cells only arise from pre-existing cells".
The Modern Tenets of the Cell Theory include:
1. all known living things are made up of cells.
2. the cell is structural & functional unit of all living things.
3. all cells come from pre-existing cells by division.
4. cells contains hereditary information which is passed from cell to cell during cell division.
5. All cells are basically the same in chemical composition.
6. all energy flow (metabolism & biochemistry) of life occurs within cells.
Robert Hooke and Cells
Robert Hooke was perhaps one of the most important scientists from the 17th century. While his research and findings were often overshadowed by those of his rival Sir Isaac Newton, one cannot argue their importance in the development of fields such as physics, astronomy, biology, and medicine, to name a few.
One must realize that Robert Hooke's advances in the field of Microscopy and Astronomy opened doors which would one day lead to discoveries from scientists such as Dr. Edwin Hubble, and that some of his other inventions such as the universal joint, which is being used in the automobile industry, and his balanced springs, which are still part of some of the watches we wear. Hooke's Law and his combustion theory are still used by today's scientists.
In 1665, Hooke published an important work titled Micrographia. This book contained a number of microscopic and telescopic observations, and some original observations in biology. In the book, Hooke coined the biological term cell, so called because his observations of plant cells reminded him of monks' cells, which were called "cellula." Hooke is often credited with the discovery of the cell, and although his microscope was very basic, research by British scientist Brian J. Ford has now shown that Hooke could have observed cork cells with it. Ford furthermore shows that Hooke used more high-power single lenses to make many of his studies. He also has identified a section in the preface that contains a description of how to make a microscope, and Hooke's design was utilized by the Dutchman Anton van Leeuwenhoek, described as the father of microbiology.
One must realize that Robert Hooke's advances in the field of Microscopy and Astronomy opened doors which would one day lead to discoveries from scientists such as Dr. Edwin Hubble, and that some of his other inventions such as the universal joint, which is being used in the automobile industry, and his balanced springs, which are still part of some of the watches we wear. Hooke's Law and his combustion theory are still used by today's scientists.
In 1665, Hooke published an important work titled Micrographia. This book contained a number of microscopic and telescopic observations, and some original observations in biology. In the book, Hooke coined the biological term cell, so called because his observations of plant cells reminded him of monks' cells, which were called "cellula." Hooke is often credited with the discovery of the cell, and although his microscope was very basic, research by British scientist Brian J. Ford has now shown that Hooke could have observed cork cells with it. Ford furthermore shows that Hooke used more high-power single lenses to make many of his studies. He also has identified a section in the preface that contains a description of how to make a microscope, and Hooke's design was utilized by the Dutchman Anton van Leeuwenhoek, described as the father of microbiology.