CELL

                                                                 

            

The cell is basic functional and structure unit of life. All the living organisms are composed of cell. All cell are division of the existing cells which in term of biology means reproduction. Every cell of our body comprises of genetic material which is passed down during the process.

Introduction of cell

The introduction to cell began back in the year 1655 when a revolutionary observation was made by an English scientist Robert Hooke. This observation made by him was so huge that it went on to change the basic biological theory and research forever. So, how was the cell discovered?

Robert Hooke was examining a dried section of the cork tree using a crude light microscope. In this analysis, he observed multiple small chambers which he named the cells. Thereafter, over the next 175 years, several kinds of research were made which led to the formation of the cell theory that we know today.

The first such theory was proposed by the German botanist Matthias Jacob Schleiden and the German physiologist Theodore Schwann in 1838. This theory was formalized in the year 1858 by the German researcher Rudolf Virchow.

Cell Theory

·         The cell is the basic functional and structural unit of life. All the living organisms are composed of cells.

·         All cells are formed by the division of the already existing cells which in terms of biology means reproduction. Every cell of our body comprises of genetic material which is passed down during the process.

·         All the basic physiological and chemical functions i.e. the growth, repair, movement, communication immunity and digestions are performed inside the cells.

·         All the activities of the cell depend mainly on the activities of the subcellular structures that lie within the cell. These subcellular structures comprise of the plasma membrane, organelles and if present, the nucleus.

·         Anton von Leeuwenhoek first saw and described a live cell.

·         Robert brown later discovered the nucleus.  

NOTE  POINT

The cell was first discovered and named by Robert Hooke in 1665. He remarked that it looked strangely similar to cellula or small rooms which monks inhabited, thus deriving the name. However what Hooke actually saw was the dead cell walls of plant cells (cork) as it appeared under the microscope.

Prokaryotic cell

 What is a Prokaryotic Cell?

Prokaryotic cells are single-celled microorganisms known to be the earliest on earth. Prokaryotes include Bacteria and Archaea. The photosynthetic prokaryotes include cyanobacteria (blue-green algae) that perform photosynthesis.

A prokaryotic cell consists of a single membrane and therefore, all the reactions occur within the cytoplasm. They can be free-living or can be found within the gut of other organisms.

·        Organism in which the nuclear material is not bounded by a definite

nuclear membrane are called prokaryotic cell.

·        It includes all the bacteria and blue green algae.

·        Placed in kingdom - monera

A  prokaryotic cell does not have a nuclear membrane. However the genetic material is present in a region in the cytoplasm known as the nucleoid. They may be spherical rod-shaped or spiral a prokaryotic cell structure is as follows.

1.    Capsule– It is an outer protective covering found in the bacterial cells, in addition to the cell wall. It helps in moisture retention, protects the cell when engulfed, and helps in the attachment of cells to nutrients and surfaces.

2.    Cell Wall– It is the outermost layer of the cell which gives shape to the cell.

3.    Cytoplasm– The cytoplasm is mainly composed of enzymes, salts, cell organelles and is a gel-like component.

4.    Cell Membrane– This layer surrounds the cytoplasm and regulates the entry and exit of substances in the cells.

5.    Pili– These are hair-like outgrowths that attach to the surface of other bacterial cells.

6.    Flagella– These are long structures in the form of a whip, that help in the locomotion of a cell.

7.    Ribosomes– These are involved in protein synthesis.

8.    Plasmids– Plasmids are non-chromosomal DNA structures. These are not involved in reproduction.

9.    Nucleoid Region– It is the region in the cytoplasm where the genetic material is present.

A prokaryotic cell lacks certain organelles like mitochondria, endoplasmic reticulum, and Golgi bodies.

Prokaryotic Cell Diagram

The prokaryotic cell diagram given below represents a bacterial cell. It depicts the absence of a true nucleus and the presence of a flagellum that differentiates it from a eukaryotic cell.

EUKARYOTIC  CELL

·       Eukaryote any cell or organism that possesses a clearly defined nucleus. The eukaryotic cell has a nuclear membrane that surrounds the nucleus in which the well-defined chromosomes (bodies containg the hereditary material) are located. Eukaryotic cell also contain organelles including mitochondria (cellular energy exchangers) a golgi apparatus (secretory device) an endoplasmic reticulum.(a canal-like system of membrane within the cell) and lysosomes(digestive apparatus within many cell type). There are several exception to this however foe example the absence of mitochondrice and a nucleus in red blood cell and the lack of mitochondria in the oxymonad monocercomonoides species.                                                                                               

·        It Includes kingdom- protists, plants, animals and fungi.