WHAT IS CELL

CELL

DEFINITION
The cell is the basic structural and functional unit of all living organisms. it is the smallest unit that can carry out all activities of life.

TYPES OF CELL
There are two main types of cells; Prokaryotic cell and Eukaryotic cell.
Eukaryotic cells have a proper nucleus and double membrane- bounded organelle. Prokaryotes in contrast, do not have a nucleus. They have a region called nucleoid in which the genetic material is located

CELL HISTORY
Ancient Greek philosophers such as Aristotle concluded that "all animals and plant are constituted of a few elements which are repeated in each of them." The elements now days called cells
Further growth and development of cell biology is associated with the development of optical lenses and to the combination of these lenses in the construction of the compound microscopes.
Robert Hooke (1635-1703) was proposed the term cell (Latin, Cella = holloow space) in 1665 He examined a thin slice cut from a peice of dried cork under the compound microscope which were built by him by using 30 multiply microscope.
Leeuwenhoek was the first to observe free-living cells such as human sperm cells etc. Robert Brown (1773-1858) discovered and named the nucleus in plant cells.n
In 1838, a German botanist Mathias Jacob Schleiden (1804-1881) put forth the idea that cells were the units of structure in the plants. In 1839, his coworker a German Zoologist Theodor Schwann (1810-1882) applied Schleiden's idea to the animals.Later, both of them postulated that the cell is the basic structural and functional unit of all living organisms.

DIAGRAM

CELL THEORY
Credit for developing cell theory is usually given to three scientists: Theodor Schwann, Matthias Jacob Schleiden, and Rudolf.
MAIN FEATURES
This theory has the following points.
*) All living organisms are composed of one or many cells.
*) All new cells arise from division of pre-existing cells.
*) Cells contain the hereditary material of an organisms which is passed from parent to daughter cells.
*) All metabolic processes take place within cells.
*) Basic chemical compostion of cells within similar species is same.

HOW ARE THE CELLS STUDIED
There are several different techniques to study cells such as:
Microscopy (includes simple light microscope, compound light microscope) differential staining, centifugation, cell/tissue culture,chromatography, electrophoresis etc.
THE EARLIEST MICROSCOPE
The simple microscope was invented by Antony Van Leeuwenhoek in 1670. This microscope was composed of only one lense and able to magnify an object up to 250 times.
Robert hook developed a microscope called the compound microscope with two set of lenses called the ocular lens and the objective lens, in this type the image magnified by the objective lense is magnified a second time by the ocular lens. These microscope rely on the light.