Cell biology
THE CELL:-
The cell is known to be the fundamental basic structural and functional unit of living organism .all living organism whether plants or animals are made-up of cells.the term cell was introduced by an English scientist "ROBERT HOOKE". cell is protoplast sorrounded by cell membrane .which is also known as plasma membrane.
(Structure of animal cell)
Cell theory:-
The cell theory was formulated by the two German scientists "Mathias schleiden and theodere Schwann" independently.they examined and observed a large variety of plant tissues and devised that all plants are composed of different kinds of cells.
The cell theory fail to explain how and from where the new cells were formed .all these observation leads to major expansion of cell theory that was expressed by RUDOLF VIRCHOW in 1855 modified the hypothesis of schleiden and Schwann and explained in his statement that cells divide and new cells are formed from pre-existing cells and the phenomena is know as "omnis cellula-e-cellula".
Types of cell:-
On the basis of organisation complexity and variety ,all cells can be grouped into two types ,i.e. prokaryotic and eukaryotic
cell.
1.PROKARYOTIC CELL:-
These are the cells that lack nuclear membrane and other membrane bound organelle.it has various components such as genetic material,cell envelope,cytoplasm,nucleoid ,inclusionbodies,ribosomes,flagella,pilli,fimbriae etc.
Nucleoid is the genetic material in case of prokaryotes that is naked,not enveloped by nuclear membrane .the outermost covering of protoplasm of the bacterial cells is called cell envelope,which protects the cell from mechanical shocks and injuries.
The cell envelope is composed of three main layers, i.e. GLYCOCALYX(mucilage sheath),cell wall and plasma membrane
Prokaryotic cells also lack the complex membrane bound organelles like chloroplast ,mitochondria etc.However some other special membranous structure are also found in them, i.e. mesosomes and chromatophores
Mesosomes are the extension of the plasma membrane into the cell in the form of vessicles,tubules and camellae .while,chromatophores are the structure present in some prokaryotes like cyanobacteria ,etc.
a)flagella,pili and fimbriae- flagella an another important feature of prokaryotes can be motile and nonmotile.Thus,motile can be motile bacteria posses one or more thread-like appendages extending from their cell wall.Each flagellum is about 1-7 micro meter long covered by a protein coat.
The flagellum is differentiate into filament,hook and basal body .pilli and fimbriae are surface structures but does not play any role in locomotion of bacteria.
Pili:-pili helps in forming conjugation tube during transfer of genetic material ,while the fimbriae helps the bacteria to attach to solid surfaces
EUKARYOTIC CELL:-
An eukaryotic cell is a cell having a well organised nucleus with a nuclear envelope along with a several membrane bounded organelles .They also posses a variety of locomotary and cytoskeletal structures.
It is seen that inspire of many similarities ,all eukaryotic cells are not exactly identical.they instead differ from echa other on the basis of individual structure and function they bear
The cell is known to be the fundamental basic structural and functional unit of living organism .all living organism whether plants or animals are made-up of cells.the term cell was introduced by an English scientist "ROBERT HOOKE". cell is protoplast sorrounded by cell membrane .which is also known as plasma membrane.
Cell theory:-
The cell theory was formulated by the two German scientists "Mathias schleiden and theodere Schwann" independently.they examined and observed a large variety of plant tissues and devised that all plants are composed of different kinds of cells.
The cell theory fail to explain how and from where the new cells were formed .all these observation leads to major expansion of cell theory that was expressed by RUDOLF VIRCHOW in 1855 modified the hypothesis of schleiden and Schwann and explained in his statement that cells divide and new cells are formed from pre-existing cells and the phenomena is know as "omnis cellula-e-cellula".
Types of cell:-
On the basis of organisation complexity and variety ,all cells can be grouped into two types ,i.e. prokaryotic and eukaryotic
cell.
1.PROKARYOTIC CELL:-
These are the cells that lack nuclear membrane and other membrane bound organelle.it has various components such as genetic material,cell envelope,cytoplasm,nucleoid ,inclusionbodies,ribosomes,flagella,pilli,fimbriae etc.
Nucleoid is the genetic material in case of prokaryotes that is naked,not enveloped by nuclear membrane .the outermost covering of protoplasm of the bacterial cells is called cell envelope,which protects the cell from mechanical shocks and injuries.
The cell envelope is composed of three main layers, i.e. GLYCOCALYX(mucilage sheath),cell wall and plasma membrane
Prokaryotic cells also lack the complex membrane bound organelles like chloroplast ,mitochondria etc.However some other special membranous structure are also found in them, i.e. mesosomes and chromatophores
Mesosomes are the extension of the plasma membrane into the cell in the form of vessicles,tubules and camellae .while,chromatophores are the structure present in some prokaryotes like cyanobacteria ,etc.
a)flagella,pili and fimbriae- flagella an another important feature of prokaryotes can be motile and nonmotile.Thus,motile can be motile bacteria posses one or more thread-like appendages extending from their cell wall.Each flagellum is about 1-7 micro meter long covered by a protein coat.
The flagellum is differentiate into filament,hook and basal body .pilli and fimbriae are surface structures but does not play any role in locomotion of bacteria.
(Flagella of bacteria)
EUKARYOTIC CELL:-
An eukaryotic cell is a cell having a well organised nucleus with a nuclear envelope along with a several membrane bounded organelles .They also posses a variety of locomotary and cytoskeletal structures.
It is seen that inspire of many similarities ,all eukaryotic cells are not exactly identical.they instead differ from echa other on the basis of individual structure and function they bear
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