The cell is the basic structural and functional unit of life. The cell is the simplest and smallest unit capable of carrying all life activities.In the unicellular organism, a single cell performs all the life activities. Hence, a cell is considered as the structural and functional unit of life. Cell biology is the biology which deals with the structure and function of cells.
R. Hooke first observed cell under the microscope. The kind of cell he observed is plant cell(dead cells) eg; cork cell. He gave the term cell where the cell is the hollow space or chamber. A.V. liver hook first observed living cells. eg; protozoans R.B.C. sperm cells. M.J. Schledemand T. Schwann is formulated cell theory.
Statement of cell theory
It refers that every living vegetative part of living plants has got all the potentialities to grow into a new plant. It was first stated by German botanist Haberlandt ( 1902 ) but later it was proved experimentally by F.C. Steward and his co - worker in 1950.
|Features||Prokaryotic cells||Eukaryotic cells|
Absence of a true or well-organized nucleus or membrane-bounded. But instead, a primitive type or so-called incipient nucleus is present.
The incipient nucleus is characterized by the absence of a nuclear membrane and the genetic material consist of highly folded, naked DNA strand without histone protein.
The absence of nucleolus.
DNA is circular.
Presence of a true membrane-bounded nucleus and the genetic material always remains associated with the histone protein.
The presence of nucleolus.
DNA is linear.
|Cell wall||Cell wall if present is chemically composed of "Murein" or "Peptidoglycans" or "Muramic acid".||Cell wall is present in plants and fungi. The chemical composition of plants is cellulose, hemicellulose, pectin and that of fungi is chitin.|
|It is one membrane system.||It is two membrane system.|
Membrane-bounded cell organelle
|Membranebounded cell organelles like mitochondria, endoplasmic reticulum, Golgi bodies, lysosomes are absent.||Membrane-bounded cell organelles like mitochondria, endoplasmic reticulum, Golgi bodies, lysosomes are present.|
|Ribosomes present - 70s type. Subunits- (The 30s and 50s) where S is sedimentation coefficient.||Ribosomes present-80s type. Subunits-(The 40s and 60s)|
Photosynthetic apparatus (Thylakoids)
|Thylakoids occur freely in the cytoplasm.||Thylakoids remain grouped inside the chloroplast.|
|Vacuoles||Absence of true or sap(liquid) vacuole but instead gas vacuoles may occur.||Present of true or sap vacuoles.|
|Cyclosis(Streaming movement of cytoplasm)||Does not occurs.||It occurs.|
|Amitotic type of cell division.||Mitotic and meotic types and sometimes amitotic also.|
|It takes 20 minutes to 1 hour.||It takes 12 hours to 24 hours.|
|In prokaryotic cell it is absent.||It is present.|
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