CELL-A cell is a structural and functional unit of all organisms. The cell was discovered by Robert hooke in 1665. In actually Hooke discover a non living cell. first living cell is discovered by Antony von Leeuwenhoek who described the algae Spirogyra. MJ Schieiden and T Schwann give the cell theory in 1839.
Cell theory-
1.All life forms are made from one to more cells.
2.New cell formed by pre existing cells.
3.A cell is a smallest form of life.
CELL SIZE- There is a wide variation in the size of cells. The smallest cells are those of mycoplama. They have a size of 0.1-1.05µm. Viruses are still smaiier. They do not have cellular structure The smallest virus has a volume of 7.0×10-7µm3.Cells of multicellular eukaryotes have a size of 5-100µm. Erythrocytes are 7-8µm in diameter. ‘small lymphocytes’ are still smaller.muscle and nerve cells are comparatively very large. Longest cells of human body are the nerve cells which may reach a length of 90cm.
Amongst plants,large cells occur
in many algae.Inter-nodal cells of CHARA are 1-10cm in length. Acetabularia, a unicellular
alga,is upto 10cm in length.In general,eggs are large sized cells because they
store food for partial or complete development of the embryo.Human egg is
slightly over 0.1mm or 100µm in diameter. Avian eggs are largest. The egg of Ostrich
is 170×150mm
with a volume of 1.1×1015µm3
LAST YEAR QUESTION PAPER WITH SOLUTION
CELL STRUCTURE AND CELL TYPES-
A plant cell consists of cell wall and protoplast,But i animal cell the cell wall is absent.In the cytoplasmic matrix are embedded a large number of cell organelles having specific functions. They are plastid,mitochondria,golgibodies,Ribosome,Centrioles,lysosomes,micofilaments,etc.
Ergastic substances are chemical substances appear in the plant bodyas products of metabolism.They may occur in the cytoplasm or in the cell wall.The various such substance are carbohydrate,proteins,fats and oils,Tannins,resins,gums,etc.
CELL TYPES-Prokaryotic and Eukaryotic
There is a two types of cells-
(a)Prokaryotic-founds in becteria,blue green algae and the PPLO(Pleuronemonia like organisms)
(b)Eukaryotic-present in animal and plant body.
PROKARYOTIC CELL
These are one enveloped structure which has a central nuclear material surrounded by cytoplasm. A bacterial cell is the best modal of an prokaryotic cell structure,Its enclosed by three layers,the outermost covering of slime,the middle cell wall and the innermost plasma membrane. parts of prokaryotic cell-
(1)Slime Layer-Capsule,Glycocalyx -This layer is present on the outer surface of the cell wall,made of polysaccharides and a polypeptide chain of amino acid,When the constituents of this layer are only polysaccharides which form a viscous layer,it is termed as slime layer.
LAST YEAR QUESTION PAPER WITH SOLUTION
CELL STRUCTURE AND CELL TYPES-
A plant cell consists of cell wall and protoplast,But i animal cell the cell wall is absent.In the cytoplasmic matrix are embedded a large number of cell organelles having specific functions. They are plastid,mitochondria,golgibodies,Ribosome,Centrioles,lysosomes,micofilaments,etc.
Ergastic substances are chemical substances appear in the plant bodyas products of metabolism.They may occur in the cytoplasm or in the cell wall.The various such substance are carbohydrate,proteins,fats and oils,Tannins,resins,gums,etc.
CELL TYPES-Prokaryotic and Eukaryotic
There is a two types of cells-
(a)Prokaryotic-founds in becteria,blue green algae and the PPLO(Pleuronemonia like organisms)
(b)Eukaryotic-present in animal and plant body.
PROKARYOTIC CELL
These are one enveloped structure which has a central nuclear material surrounded by cytoplasm. A bacterial cell is the best modal of an prokaryotic cell structure,Its enclosed by three layers,the outermost covering of slime,the middle cell wall and the innermost plasma membrane. parts of prokaryotic cell-
(1)Slime Layer-Capsule,Glycocalyx -This layer is present on the outer surface of the cell wall,made of polysaccharides and a polypeptide chain of amino acid,When the constituents of this layer are only polysaccharides which form a viscous layer,it is termed as slime layer.
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