class 11 ncert biology,cell theory,cell biology handwritten notes hindi

11TH BIOLOGY ALL NEET POSTS

Cell structure and function
All Organisms are composed of structural and functional units of life called cells. The body of some organisms like Bacteria Protozoa and some algae is made up of a single cell where as the body of higher fungi plants and animals are composed of many cells. Human body is built of about 1 trillion cells.
The cell and cell theory
Landmarks in the study of a cell
Soon after Anton Van leeuwenhoek invented the microscope Robert hooke in Seoul 165 observed a piece of cork under the microscope and found it to be made of small compartments which he called cells Latin cell barabar small room 6072 Livon Hawk observed bacteria sperms and red blood corpuscles all of which were sales much letter in 1831 Robert Brown in English man observed that all cells had a centrally position body which terminator the nucleus
Cell theory
1838 MJ schleiden and theodor schwann formulated the cell theory which maintenance that all organisms are composed of cells cell is the structural and functional unit of life and cells arise from preexisting cells cells very considerable and shapes and sizes Nerve cells of animals have long extensions they can be several sentimeter and length muscle cells are located in shape of the ostrich is the largest cell 75 mm some plant cells have thick walls there is also wide variation in the number of cells in different organisms
The cell
A cell may be defined as a unit of Protoplasm bound by a plasma or Cell Membrane and processing A nucleus Protoplasm is the life giving substance and includes the cytoplasm and the nucleus the cytoplasm has init organelles such as ribosomes mitochondria Golgi body plastids lysosomes and endoplasmic reticulum plant cells have in their cytoplasm and large vacuoles containing non living nuclear inclusions like crystals pigments the bacteria have neither defined cell organelles nor a well formed nucleus but every cell has three major components
Plasma membrane cytoplasm DNA naked in bacteria and enclosed by a nuclear membrane in all other organisms
Two basic types of cells
Psychologists recognise two basic types of cells their differences have been tabulated below in organisms which do not possess a well formed nucleus are prokaryotes such as the bacteria all others possess a well defined nucleus covered by a nuclear membrane they are eukaryotes
The Eukaryotic cell
You provide true karyon barabar nucleus
Nucleus distinct with well formed nuclear membrane double membrane cell organelles chloroplast mitochondria nucleus and single membrane and Golgi apparatus lysosomes vehicle endoplasmic reticulum are present songs 80s district compartments in the Sel IE the cytoplasm and nucleus depending upon the species number of chromosomes per nucleus where is from 2 to many is chromosome is liner whether its two ends free is chromosome has one liner double stranded DNA Complex with stones is chromosome has one send through metre that divides a chromosome into two arms however if the centromere is terminal the chromosome would have only one arm
The prokaryotic cell
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Nucleus not distinct it is in the form of a nuclear zone nuclear nuclear membrane absent single membrane and cell bodies like mysms present endoplasmic reticulum plastids and mitochondria microbodies like lysosomes and Golgi body absent ribosomes 70 no Cup Apartments there is only one chromosome personal the chromosome is circular and remains attached to cell membrane at one point the chromosome has single double standard circular DNA molecule and is not associated with stones the chromosome legs a centromere.
Svedberg unit
When the sale is fractionated or broken down into its components by rotating in a ultracentrifuge at different speeds the ribosomes of Eukaryotic and prokaryotic cells sediments settle down at different speeds the coefficient of sedimentation is represented in sweat work unit is depicted as S
Cell and the animals cell also differ in several respect
The plant cell
Cellulose cell wall present external two cell vacuoles are usually large plastids present Golgi body present in the form of units known as dictyosomes centriole absent
Animal cell
No cell wall outermost structure is cell membrane or plasma membrane generally vacuoles are absent and if present are usually small plastids sent Golgi body well developed having two sister Ne Central present

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