Cell

           

                                 Cell

Cell is the Fundamental, structural and functional unit of any organism.

Discovery of the cell-

Cell is discovered by "An English Scientist Robert Hooke in 1665. He saw hive like structure in the bark of a stem of a tree under a self made microscope. This microscope was v simple type. He saw that there are some hives like structure in the cork of stem. He told this 'cell' whose meaning is "Little room"in latin Language. He also published a book "Micrographia"in 1665.

Antony Leeuwenhoek was a microscopist who made an improved microscope in 1674. and discovered the free living cells likeAmoeba,bacteria Paramecium,chlamydomonas  (algal cell) in pond water. He identified the sperm cells of human being, dogs, rabbit, frogs and insects etc.

                 Antony Van Leeuwenhoek

Amoeba(Cell)

A typical bacterium Cell

Robert Brown (Scottish botanist)
discovered Nucleus in plant cell.

J. E. Purkinje(Animal Physiologist) in 1839 gave the term Protoplasm for the living fluid present inside the cell.

 Cell theory-

Jacob Matthias Schleiden,and Theodor Schwann gave cell theory in1838-1839. According to this theory, all plants and animals are composed of cells.

German biologist, R.Virchow refined this theory and gave the idea the all the cells arise from pre-existing cells (omnis cellula a cellula). and gave the following postulates about the cells.

1-All organisms are composed of cell or cell products.
2-All metabolic reactions take place in the cells.
3-Cells are structural and Functional unit of life.
4-All cells arise from pre-exusting cells.
5-Every organisms starts its life from a single cell.
6-No cell originate spontaneously.
7-Viruses are exception to the cell theory.

Microscopes used-

Light Microscope- Light or compound microscope is used in observing the cell. This is the same microscope that is used in the lab by the students.Many lenses are combined together so as to magnify the image. Its magnification power ranges 300 to1500 times. 

Electron Microscope-

This microscope was developed by  German Scientists, Koll and Ruska in 1932 and put to use in 1940. This microscope has Electromagnets for magnificatio and Electron  for illumination.

Types of 0rganisms on the basis of no. of cells

Unicellular cell-

The organisms which arecomposed of a single cell or called unicellular organisms. The whole functions of life are performed by the single cell eg. Amoeba, Paramecium,Euglena.

Multicellular organisms-

The organisms which are composed of more than one cell are called multicellular organisms. Eg. Human being , Frog, Fish , snake ,birds etc.

Human being

Indian frog

Rana tigrina

Fish

All the organisms on this earth are divided into two types.
1-Non-cellular organisms 
2-Cellular organisms
Noncellular organisms-These organisms do not have any cell in their body organisation e.g. Mycoplasma, Viruses.

Viruses-
Viruses are thought to be connecting link b/w living and non-living organisms.These can reproduce but use machinery of other living organisms. These can be crystalised and cause diseases and vary their shape. These can have DNA or RNA as genetic material. These can perform Reverse transcription process means can transcript DNA from RNA. 
Reverse transcription is seen in Retrovirus only. The genetic material in these viruses is RNA.

 Mycoplasma-

Mycoplasma are smallest bacterial cell discovered yet. These do not have cell wall but have cell membrane around itself. These can live or survive without oxygen and come in various shapes eg.Mycoplasma genitalium is flask shaped while Mycoplas..
pneumoniae is more elongatedMycoplasma may be parasitic or saprophytic in nature. The characteristics of Mycoplasma make them more resistant to many common antibiotics  peniciliumor other betalactum
Mycoplasma also known Pleuroneumoniae like organism (PPLO).

Cell on the basis of development.

1-Prokaryotic cell
2-Eukaryotic cell

Prokaryotic cell-These cells are primitive and v simple type cell. These have incipient nucleus and organelles are found less in no.
means few organelles are found for functioning of the cell. Altimately these are undeveloped cells.

1-These cells do not have double membrane covered organelles.

2-The Ribosimes are of 70S type.

3-DNA is found in the cytoplasm , if found in the nucleus then nucleus is not beleagured by plasmamembrane.

4-Chloroplast, Mitochondria, Golgi Apparatus like organelles are absent.

5-Sometimes some extra molecules of DNA is found which takes part in DNA replication . This is called Plasmids.

6-These cells are smaller in size than eukaryotic cells.

7-These cells are surrounded by Plasma membrane.

Eukaryotic cell-These are developed cells because these have all those organelles which prrform v important and advanced role in seviving of the cell eg Mitochondria, Golgi apparatus, Chloroplast or Centrosome
  
1-These cells possess the nucleus in which DNA is found and these  are
beleagured by double plasma membrane.

2-These cell do not have plasmid but DNA material is more than prokaryotic cell in quantity.

3-DNA material is in the form of chromosomes which are safe in nucleus.

4-These cells have 80 S Ribosomes.

5-These cell have more than one chromosome

6-These cells have Nucleolus in the middle nucleus.