Page 5 - Cell biology PDC 2024
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CHAPTER 1
THE CELL AND ITS ORGANELLES
Cell biology
Cellular biology or cytology: it is the study of cells.
The cell: (from Latin cella, meaning "small room) is the basic structural,
functional, and biological unit of all known organisms.
A cell is the smallest unit of life.
Cell theory
The classical cell theory was proposed by Theodor Schwann in 1839.
There are three parts to this theory:
1. All organisms are made of cells.
2. Cells are the basic units of life. This was based on a conclusion
made by Schwann and Matthias Schleiden in 1838, after
comparing their observations of plant and animal cells.
3. Cells come from preexisting cells that have multiplied, was
described by Rudolf Virchow in 1858
Modern cell theory
It has three main additions:
1. DNA is passed between cells during cell division.
2. Cells of all organisms within a similar species are mostly the
same, both structurally and chemically.
3. Energy flow occurs within cells.
There are 2 types of cells: prokaryotes and eukaryotes
a) Prokaryotes
ex: bacteria and archaea.
• Prokaryotic cells were the first form of life on Earth, characterized
by having vital biological processes.
• They are simpler and smaller than eukaryotic cells, and lack a
nucleus, and other membrane-bound organelles. The DNA of a
prokaryotic cell consists of a single circular chromosome that is in
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