What is a cell?
A cell is the smallest functional unit of any living organism. It is the smallest part of any organism which is capable of existing and functioning independently.
It was first discovered by Robert Hooke in 1653. Matthias Schleiden, a German botanist and Theodor Schwann, a German zoologist have been credited with The Cell Theory, 1839.
Examples of unicellular and multicellular organisms
Single – celled Organisms : Amoeba, Bacteria and Yeast.
Multi – celled Organisms : Almost all plants and animals and fungus.
Cell anatomy and physiology
The living parts of the cell:
1. The cell membrane and cell wall
A cell is surrounded by a cell membrane or plasma membrane. The cell membrane has fine pores through which it allows selective substances to pass through.
The cell wall is found in plant cells and surrounds the cell membrane. It is made up of cellulose. This cell wall gives shape and makes it rigid, it also allows the free flow of substances.
2. Cytoplasm
Cytoplasm is a colourless, semi liquid substance found within the cell membrane. Cell organelles are suspended within it. It is the site of many biochemical reactions.
The cytoplasm has the following cell organelles –
- Endoplasmic reticulum
- Ribosomes
- Mitochondria
- Golgi apparatus
- Lysosomes
- Centrosome and centrioles
- Plastids
3. Nucleus
The nucleus is the largest cell organelle, it is dense and spherical present in the center of the cytoplasm. It’s main function is the regulation of cell functions and contains the chromosomes. It regulates all the hereditary activities of the cell.
It consists of
- Nuclear Membrane
- Nucleolus
- Chromatin fibers.
The non – living parts of the cell:
1. Granules
These are small crystal particles present in the cytoplasm. They contain starch and glycogen.
2. Vacuoles
These are certain clear places filled with water present in the cytoplasm. The fluid in them is called cell sap. Vacuoles give turgidity to the cells.
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