Cell structure and function
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Robert Hooke first observed cells in 1665 when examining slices of cork under a microscope. He described the structures as "little boxes". Anton van Leeuwenhoek later discovered living cells. The Cell Theory states that all living things are made of cells, cells are the basic unit of structure and function in organisms, and new cells are produced from existing cells. Cells vary in size from bacteria at 0.1-0.5 micrometers to ostrich egg cells at 170mm by 130mm. They also vary in shape from round to elongated to branched. Cells are either eukaryotic, containing a nucleus and organelles, or prokaryotic, lacking these structures. The basic parts of a cell are the cell
Cell structure and function
- 1. Class 8 CELL – STRUCTURE AND FUNCTION Angali Kumari Roll no. 14
- 2. In 1665, Robert Hooke observed slices of cork (dead cells) under microscope. He described what he observed as “little boxes”. Anton Van Leeuwenhoek was the first person to discover a living cell. DISCOVERY OF CELL
- 3. Cell Theory was – All living things are composed of one or more cells. Cells are organism’s basic units of structure and function. Cells come only from existing cells. CELL THEORY
- 5. The size of cells may be as small as a millionth of a meter (micron) or may be as large as a few centimeters. The smallest cell is 0.1-0.5 micrometer in bacteria and largest cell measuring 170mm X 130 mm is an ostrich’s egg. 1. SIZE
- 6. Cells may be round, spherical, elongated. Some are long and pointed at both ends. Some are branched like nerve cells. The change in shape is due to formation of pseudopodia(false feet) which facilitates cell movement and capturing of food. 2. SHAPE
- 7. On the basis of internal organisation, a cell can be – a) Eukaryotes b) Prokaryotes Eukaryotes are those cells, which contains nucleus and membrane-bound organelle. Prokaryotes are those cells, which are without nucleus and membrane-bound organelle. 3. INTERNAL ORGANISATION
- 8. Basic Components of a cell Cell Membrane Cytoplasm Nucleus PARTS OF CELL
- 9. Cell Membrane • Cell membranes are also known as “plasma membranes”. • The membrane separates cells from one another and also from the surrounding medium. • It gives shape to the cell. • In plants, in addition to cell membrane an outer layer known as “cell wall” is present to protect the cell from harsh environment.
- 10. Cytoplasm • It is jelly-like substance present between cell membrane and the nucleus. • Other Organelles of cell are present in the cytoplasm. Nucleus • Nucleus is known as “brain of the cell”. • It is separated from the cytoplasm by a membrane called nuclear membrane. • In addition, it contains thread-like structures called chromosomes, which carries gene from parent body to its off springs.
- 11. STRUCTURE
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