Concept of the cell
The cell is the smallest structural unit of the organization of the living body. The organisms composed of a single cell are called unicellular organisms and those of many cells are called multicellular organisms. Cells perform different functions in the body.
For example - The transportation of oxygen is done by red blood cells. Transmission of impulses is done by neurons. Accordingly, the smallest bio unit that is adapted to perform a particular function is the cell. So it is clear that the structural and functional unit of life is the cell. The cells differ from one another from their shape, size and function. Except few occasions, mostly cells are not visible to the naked eye. Therefore they have to be observed using the light microscope.
Typical cell The small structures present within the cell to perform different functions are known as organelles.The types of organelles and the number of them differ according to the function performed by the cell. The cell prepared by including all the organelles is known as the typical cell. In the living world such cells do not exist. But cells with a certain number of organelles of the typical cell can be found in living organisms.
All animal cells are covered by a plasma membrane or a cell membrane. It is a live semi permeable membrane as well as a selective permeable membrane. There is a centralized nucleus in an animal cell. The cytoplasm is a gelatinous material. The outer covering of the plant cell is the cell wall . It is made up of cellulose. Inner to the cell wall is the plasma membrane. At the center of plant cell is a large vacuole. Generally there are no such vacuoles in animal cells. Animal cells as well as plant cells possess different organelles that perform different functions. Most of the above organelles cannot be observed through the light microscope. Therefore the electron microscope should be used. Below are the typical plant and animal cells created based on electron microscopic information.
