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Showing posts from April, 2024

An overview of cell

  A typical plant cell, has a distinct cell wall as its outer boundary and just within it is the cell membrane . Cells that have membrane bound nuclei are called eukaryotic whereas cells that lack a membrane bound nucleus are prokaryotic . in both prokaryotic and eukaryotic cells,  a semi- fluid matrix called cytoplasm occupies the volume of the cell. The cytoplasm is the main arena of cellular activities in both the plant and animal cells. various chemical reactions occurs in it to keep the cell in the living state., Besides the nucleus, the eukaryotic cells have other membrane bound distinct structures called organelles like the endoplasmic reticulum (ER), the golgi complex, lysosomes, microbodies . the prokaryotic cells lack such membrane bound organelles. Ribosomes are non-membrane bound organelles found in all cells - both eukaryotic as well as prokaryotic cells. Within the cell, ribosomes  are found not only in the cytoplasm but also within the two organelles chloroplast (in plan

Cell theory

In 1838, Matthias Schleiden , a German botanist , examined a large number of plants and observed that all plants are composed of different kind of the cell which form the tissue of the plants . at about the same time Theodore Schwann  (1839) , a British Zoologist ,studied different type of animal cell and reported that cells had a thin outer layer which is today known as the plasma membrane . He also conclude, based on his studies on plant tissue, that the presence of the cell wall is a unique character of the plants cells. Schwann proposed the hypothesis that the bodies of animals and plants are composed of the cells and products of cells . Schleiden & Schwann together formulated the cell theory . this theory however , did not explain as to how new cells were formed . Rudolf Virchow (1855) first  explained that cells cells divided and new cells are formed from pre-existing cells (Omnis cellula-e-cellula). He modified the hypothesis of Schleiden and Schwann  to give the cell theo

What is cell

 All organisms are composed of cell. Some are composed of a single cell and are called unicellular organisms while others, like us, composed of many cells, are called multicellular organism . unicellular organism are capable of (1) independent  existence and (2) performing the essential functions of life . Anything less than a complete structure if a cell does not ensure independent living . Hence, cell is the fundamental structure and functional unit of all living organisms. first cell was discovered by - ROBERT HOOKE in thin slice of cork. Anton von Leeuwenhoek first saw and describe a living cell . Robert Brown later discovered the nucleus .