A cell is the basic unit of life. The modern cells theory states that :
All living organism are made up of one or more cells.
New cells are formed by the division of pre existing cells.
Cells contain genetic material of an organism which is
passed from parent to daughter cells.
All metabolic reaction take place with in cell.
A cell consists of protoplasm surrounded by plasma membrane.
Some organism have a non living cell wall on outer most layer. Some organism
are unicellular, they are made up of just one cell. Other organism are
multicellular and consists of many cells. Cells is divided into 2 categories :
a.
Prokaryotic cells, (pro, before; karyon,
nucleus) which include bacteria and archae have DNA enclosed by nucleus membrane
and lack organelles bounded by a double membrane.
b.
Eukaryotic cells (eu, true) which include the
protoctists, fungi animals and plants have chromosomes surrounded by well
defined nuclear membranes.
Table the different of prokaryoict and eukaryotic
Prokaryotic
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Eukaryotic
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Examples are bacteria
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Examples are plants
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Average diameter of cell 0,5-5 µm
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Average diameter of cell 10- 100 µm
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Genetic materials is circular double strand of DNA not surrounded by
double membrane nuclear envelope.
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Most DNA are associated with histone protein to form chromosomes.
Chromoshomes are surrounded by double membrane nuclear envelope . Circular DNA
are present in mithocondrion and choloroplast.
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Some bacteria have small circular DNA called plasmid
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Plasmid are absent.
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Few organelles. No double membrane bound organelle such as
mitochondrion and chloroplast.
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Many organelle . Presence of double membrane organelle such as
nucleus, mitochondrion and choolroplast in plant and algae
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No mitosis or meiosis
No spindle formation, just binary division
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Mitosis, meiosis or both can occur. There is spindle formation.
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Ribosomes are smaller, 70 Svedberg. ribosomes occur as free particles
in cytoplasma
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Ribosomes are larger, 80 Svedberg. Ribosomes occur as free particle
or are bounded to endoplasmic reticulum
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Rigid cell walls containing murein (peptidoglycan)
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Cell walls of plants and algae contain cellulose, fungi contain
chitin and animal cells have no cell walls.
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Mesosomes in bacteria and plasma membrane of cyanobacteria contain
respiratory enzym. No mithocondrion
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There are no mesosomes . Mitochondria function as sites for cellular
respiration to produce ATP
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Some prokaryotic are photoautrotophs. Photosinthetic membranes not
staked into grana. No chloroplast
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Chloroplast containing grana
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Flagella, if present, contain flagellin and lack of microtubules.
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Flagella, if present have a “9 + 2” formula arrangement of
microtubules
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Some prokaryotic cells have enzym that can fix atmospheric nitrogen
for use in amino acid synthesis
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Eukaryotic cells do not contain enzym that can fix atmospheric
nitrogen
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