Cell
Cell
Cell - The cell is the fundamental unit of life. All plants and animals are made up of cells. Cell is the microcosm (having a definite boundary with in) which constant chemical activities and flow of energy proceed. Cell is the structural and functional unit of all organisms.
The body of an organism may contain one cell as in Unicellular organisms. Each cell has the capacity to perform all vital activities like nutrition, growth, respiration, irritability, movement and reproduction etc.
Discovery of cell -
The cell was discovered by the scientist Robert Hooke in 1665, when he worked on the wooden cork. He cut the thin slices of wooden cork and see these thin slices of cork in the self made microscope. Then he saw the honey comb like structures .
These structures are called cell by the scientist Robert Hooke in 1665.
** The cell which is discovered by the scientist Robert Hooke was a dead cell.
** The first living cell (Bacteria)was discovered by the scientist Antony wan Leeuwenhack in 1674.
Cell theory -
The cell theory was propounded by German biologist Schleiden , lawyer turned botanist (1838) and Theodor Schwann , a zoologist (1838) .
The two important points of cell theory are -
(1) In sprite of enormous diversity of living organisms, All organisms are composed of one or more cells.
(2) The cell is the structural unit of life.
Types of cell -
Living cells may be divided into two types-
(1) Prokaryotic cell (Gr. Pro = primitive, Karyon = nucleus )
These cells have incipient nucleus ie. Nucleus without nuclear membrane. These cells lake membrane bound cell organelles. Naked DNA is found diffused in central part of cell.
For example- Bacteria, Blue green algae etc.
(2) Eukaryotic cell ( Gr. Eu = True, Karyon = nucleus )
Eukaryotic cells possess true nucleus which is well organised. Nucleus is surrounded by nuclear membrane and nucleolus associated nucleoplasm and chromatin network, DNA is associated with histone protein.
For example- Plant cell, Amoeba,Paramecium,Euglena etc.
Cell size and cell shape -
There is large variety in cell size and shape. Most of the cells are very small and their volume ranges from 1 to 1000 cm3. The smallest cell observed so far is PPLO , about 0.1 is diameter. The largest cell is egg of Ostrich, measuring 25 cm . Angove cell may be 1 meter long. Shapes of cells may be oval, spherical, isodiametric , fibrous, elliptical, columnar , polygonal etc.
Cell - The cell is the fundamental unit of life. All plants and animals are made up of cells. Cell is the microcosm (having a definite boundary with in) which constant chemical activities and flow of energy proceed. Cell is the structural and functional unit of all organisms.
The body of an organism may contain one cell as in Unicellular organisms. Each cell has the capacity to perform all vital activities like nutrition, growth, respiration, irritability, movement and reproduction etc.
Discovery of cell -
The cell was discovered by the scientist Robert Hooke in 1665, when he worked on the wooden cork. He cut the thin slices of wooden cork and see these thin slices of cork in the self made microscope. Then he saw the honey comb like structures .
These structures are called cell by the scientist Robert Hooke in 1665.
** The cell which is discovered by the scientist Robert Hooke was a dead cell.
** The first living cell (Bacteria)was discovered by the scientist Antony wan Leeuwenhack in 1674.
Cell theory -
The cell theory was propounded by German biologist Schleiden , lawyer turned botanist (1838) and Theodor Schwann , a zoologist (1838) .
The two important points of cell theory are -
(1) In sprite of enormous diversity of living organisms, All organisms are composed of one or more cells.
(2) The cell is the structural unit of life.
Types of cell -
Living cells may be divided into two types-
(1) Prokaryotic cell (Gr. Pro = primitive, Karyon = nucleus )
These cells have incipient nucleus ie. Nucleus without nuclear membrane. These cells lake membrane bound cell organelles. Naked DNA is found diffused in central part of cell.
For example- Bacteria, Blue green algae etc.
(2) Eukaryotic cell ( Gr. Eu = True, Karyon = nucleus )
Eukaryotic cells possess true nucleus which is well organised. Nucleus is surrounded by nuclear membrane and nucleolus associated nucleoplasm and chromatin network, DNA is associated with histone protein.
For example- Plant cell, Amoeba,Paramecium,Euglena etc.
Cell size and cell shape -
There is large variety in cell size and shape. Most of the cells are very small and their volume ranges from 1 to 1000 cm3. The smallest cell observed so far is PPLO , about 0.1 is diameter. The largest cell is egg of Ostrich, measuring 25 cm . Angove cell may be 1 meter long. Shapes of cells may be oval, spherical, isodiametric , fibrous, elliptical, columnar , polygonal etc.
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