genbio1.1

• Cell is the basic structural and functional unit of living organisms.
• In 1665, British scientist Robert Hooke examined a piece of cork and found a little structures in it which he compared to cellulae. He named it cells, it was then discovered that the cell he found were outer wall of the plant cell.
• In the late 1600's, Dutch scientist Anton van Leeuwenhoek examined different subjects, using a refined microscope than that of Hooke.Leuwenhoek found moving protist and sperm, which he collectively termed "animalcules"
• When Leeuwenhooek observed his teeth scrapings, he found animalcules shooting and spinning inside the cell.
• in 1838, German botanist Matthias Jacob Schleiden established that the small compartments in his plant specimens are cells.
• In 1839, a German zoologist named Theodore Schwann after doing microscopic studies of animal cells, instituted that all animals are also composed of cells.
• 1590 Zacharias Janssen invented a primitive microscope with the help of his father Hans
• 1665-1676 Marcello Malpighi and Nehemiah Grew conducted separated investigations on plant cell. They determined the presence of organelles within its cells.
• 1831- Robert Brown made a series of discoveries about cell organelles and ultimately discovered the nucleus. This became a major breakthrough in the history of biology.
• 1838 Matthias Schleiden microscopically examine plants and recognized that plant parts come from cells. In his writings in Contribution in Phytogenesis, he proposed that the different structures of a plant are all composed of cells.
• 1839 Theodore Schwann declared that animals are likewise composed of cells. This put an end to the debates - whether or not plants and animals are different in structural origin and composition.
• 1840 Albrecht von Roelliker stated that sperm and egg are composed of cells and that all humans are configured from cells.
• 1849 Louis Pasteur was developing fermentation, a process to kill bacteria, he proved that bacteria are able to multiply and that bacterial cells come from other bacterial cells.
• 1858 Rudolf Virchow declared, "Omnis cellula e cellula" which he meant that cells come from pre- existing cells. With this conclusion, the cell theory was completed.
• Most cells are very small (microscopic), some may be very large (macroscopic).
• The unit used to measure size of a cell is micrometer.
• 1 µm = 1/1000 millimeter
• Smallest cell: Mycoplasma Size: 0.1 µm
• Largest cell: Ostrich egg Size: 18 cm
• Smallest cell in human: Sperm cell Size: 5 µm
• Largest cell in human: Ovum cell Size: 120 µm
• Longest cell: Nerve cell Size: 1 m
• shape of cells depends mainly upon the function of cells.
• Some cells like Euglena and Amoeba can change their shape, but most cells have a fixed shape.
• The detailed structure of a cell has been studied under compound microscope and electron microscope.
• The structure of a cell as seen under an electron microscope is called ultrastructure.
• first postulate: cell is the unit of life
• second postulate: all living organisms are composed of cells
• third postulate: new cells came from pre-existing cells