CELL ;   It is the basic structural and functional unit of all form of life .All living forms are composed  of  microscopic units called cell The study  of structure and  composition  is called Cytology. Cell was first  discovered and observed by ROBERT HOOKE in a thin dead sclice of crock in year 1665 . First living cell was discovered by A. V. LEEUWENHOCK in 1674 . 

Protoplasm is an aggregate of  various chemicald such as water, ions, salts and other organic molecules like protiens , carbohydrates, fats, nucleic acids, vitamins . Presents in cytoplasm  along with cell organelles and nucleus that constitute a cell . It exists in sol – gel state.

CELL THEORY :  The two biologist SCHLEIDEN and  SCHWANN  in1838 gave the cell theory as All  plants and animals are composed of cells which are the basic unit of life and arises from pre existing cell ( Viruses is the exception of cell theory )

TYPES OF CELLS  : Prokaryotic cell such bacteria, blue green algae or cyanobacteria Eukaryotic as Paramecium, Amoeba , ostrich or pine tree

PROKARYOTIC CELLS :  they are very small in size about 1 – 10^-,6 m , Nuclear region is not surrounded  by nuclear membrane so nucleolus are absent  ,always found in unicelled organism, single chromosome is present in it Cell division by fission / budding and membrane bound  cell organelles are absent such in  Bacteria

EUKARYOTIC CELLS : They are fairly large in size of 5 – 10 pico m, Nuclear material surrounded  by a  nuclear membrane so  nucleolus is present it may be unicellular or multicellular , more than one chromosome are present cell division takes place by  mitosis or meiosis. Membrane bound cell organelles are present such as all plants, animals , amoeba

ORGANISMS ARE OF TWO TYPES : unicellular  organism and multicellular organism. In the unicellular organism are single cell ,they are simple in nature ,all functions are performed by single cell  , division may or may not be performed ,reproduction involved the same single cell their life spam is short . eg amoeba, paramecium, bacteria . In case of Multicellular organism  where there are large number of cells having complex  , different cell perform different  specific function , The specialised cells/gem cells take part in reproduction  their life span is long .

CELL SHAPE : Cells are of variable shapes ad sizes. That varies is according to their function position  .Generally cell are spherical but they may be elongated as nerve cell ,branched as pigment discoidal in RBC  spindle shaped as muscle cell .  It has squamous epithelium cells , Ciliated epithelium  form  Trachea, columnar cells in the stomach,  smooth muscle  that form intestine, Red blood cells/Erythrocytes , WBC, Nerve cell , sperm and  ovum .

CELL SIZE  :  The size of cells is variable depending upon it’s position and function. Some are microscope while some are visible with naked eyes. Their size may vary  from .2 pico m to 18 pico cm. Size of typical cell in a multicellular  organism ranges  from 2 – 120 micron . The largest cell is Ostrich egg (15cm x13cm ) weight 1.4kg The longest cell is nerve cell up to 1 meter the smallest cell so far known as PPLO  as mycoplasma .

COMPONENT OF CELLS :  There is  an occurrence of division of labour  within a EUKARYOTIC  cell as they all got certain specific components called  cell organelles. Each of them perform a specific function .Three basic  components of all the cell are  the plasma membrane, nucleus and cytoplasm.

CELL MEMBRANE/ PLASMA MEMBRANE : Plasma membrane is selectively permeable in nature , means it allows or permits the entry and exit of  some materials in and out of the cell. The cell membrane is also called plasma membrane/plasma lemma.It is the limiting boundary of each cell which separates  cytoplasm from its surroundings. It is found in both plant as well as animals cells. It is  the outermost  covering of the cell incase of the animals and lies below the cell wall incase of plants . As per  lipid  model of plasma of plasma  membrane. It is made of  proteins and lipids where  proteins are the sandwiched between  bilayer of lipids SINGER AND NICHOLSON  gave the fluid mosaic model or lipid bilayer model of plasma membrane. It is flexible and can be  folded, broken and reunited

FUNCTIONS  : It regulates the movement of the molecules inside and outside the cell , it helps in maintaining the distinct  composition of the cell

TRANSPORTATION OF MOLECULES ACROSS THE PLASMA MEMBRANE : Diffusion  is the movement  of solutes/ ions from the region of higher concentration to lower concentration ,it does not require any energy so it is called passive transport it do not require any semipermeable membrane

Osmosis is the movement of solvent/ water from  higher concentration to lower concentration solvent through semipermeable membrane . In other words the movement of water across semipermeable membrane is also osmosis It is also called diffusion of solvent.

There are two kinds of osmosis  i) Endosmosis in which the movement of solvent into the cell takes place ii) Exosmosis in which the movement of solvent takes place outside the cell

Types of Solution a) Isotonic Solution in this kind the  solution in which concentration of the solution outside the cell is equal to the concentration of the cytoplasm  of the cell  b) Hypertonic Solution is the solution in which the concentration of the solution outside the cell is more than the concentration of the cytoplasm of the cell due to this cell loses water and become plasmolyzed c)Plasmolysis is the shrinking of the  protoplasm away from the cell wall due to loss of water (exosmosis ) d) Hypotonic Solution is that kind of solution where the concentration of the solution out side the cell is less than the cytoplasm of the cell due to which water flows inside the cell get swell or may burst

CELL WALL :It is the outermost covering of the plant cells and te cell of fungi but absent in animal cells. Cell wall is rigid , strong, thick porous and non living  structure. In plants it is made up of cellulose and hemi celluloses. In Fungi it is primarily made up of chitin. Cell walls of two adjacent cells are joined by a layer called middle lamellae  and microscopic channels known as plasmodesmata for transport

Functions : The cell wall provide strength  definite shape, structure , support and protection of the cell It is permeable and allows the entry of molecules of different sizes and control intercellular transport.

NUCLEUS  : It is the most important cell organelle which directs  and control all cellular activities, also called headquarters of the cell/ controller of cell discovered by ROBERT BROWN IN 1831 It is well defined in EUKARYOTES  but absent in PROKARYOTES. ( It contain  primitive nucleus  called  Nucleoid ) The Nucleus has double layered covering called nuclear membrane and also contain nucleolus and chromatin material  which is made up of DNA (DEOXY RIBONUCLEIC ACID ), Protein which condense to form chromosome . These Chromosome/ chromatin consist of DNA which  stores and transmits the hereditary information for the cell function, growth and reproduction. The functional segment of  DNA is genes

Function : It  directs and control all the metabolic activities of the cell and regulate the cell cycle , it also help in transmission of hereditary characters from the parents to the offsprings

CYTOPLASM : It is the fluid  content  enclosed by plasma membrane discovered by KOLLIKER IN1862 It is the site  of both biosynthetic and  catabolic pathway ie metabolic activities It is divided in two parts  a) Cytosol which is aqueous soluble part contain various fibrous proteins  forming cytoskeleton containing water , protein , carbohydrate b)Cell Organelles it is the living part of the cell having definite shape , structure and function bounded by plasma  membrane

Single membrane bounded cell organelles   are ER , Lysosomes , Golgi bodies , Vacuoles and  peroxisomes

Double bounded cell organelles are mitochondria , plastids  ( they have their own DNA material )

Non membrane bounded  cell organelles are Ribosome , Centrosome and microtubules.

ENDOPLASMIC RETICULUM :It is the net work of the membrane bound tubules and sheet  present in cytoplasm. Discovered by GARNIER  and structure was given by Porter  Claude and Fullum. These are present in all  cells  except  prokaryotes and mammalian erythrocytes.

ER are of two type a) SER ( smooth endoplasmic reticulum )   mainly made up of tubules , it helps in steroid , lipids and polysaccharides synthesis  and ribosomes are absent in it  b) RER ( Rough endoplasmic reticulum) which is made of Cisternae and vesicles , helps in protein synthesis  and contain ribosomes on the surface .

FUNCTION :  It is the organelle which serve as a channel for the transport of material between various regions of cytoplasm and its nucleus . It also work  like cytoplasm framework to provide surface for some of the biochemical activities it form endoskeleton of cell. Itis also in the synthesis of fats, protein , steroids cholesterol SER plays important role in detoxification  of drugs  and poisonous products It is the membrane of biogenesis protein, lipids produced by ER are used to  produce cell membrane .

GOLGI BODIES :It consist  of the system of the membrane bounded  fluid filled  Vesicles arranged parallel to each other in the sack  called Cisternae along with some large and spherical vesicles. It was discovered by CAMILLO GOLGI It is absent in  prokaryotes , mammalian RBC and sieve cells

FUNCTION ; The main function is storage, modification, packaging  and secretion  of products in vesicles.  It involves in the formation of lysosomes . It is  secretary in nature and helps in melanin synthesis and  helps i the synthesis of cell wall and plasma membrane.

MITOCHONDRIA : It is round shape structure foundin cytoplasm  of all  eukaryotic cells except mammalian RBC and also absent in  prokaryotes It was first seen by KOLLIKER in the insect cells in 1880 It is also called  Power House of cell or storage battery .It is double membranous  structure  where the outer membrane has specific proteins while inner membrane  is folded inside to form the chamber called Cristae It has it’s own DNA and  Ribosomes .

FUNCTION  The main function is to produce, store and release the energy in the form of ATP ( Adenosine Triphosphate ) the energy currency of cell , it is the site of  cellular respiration (Kreb cycle) in which ATP is produced .

RIBOSOMES ; It is the site of protein synthesis all structural and functional protein/ enzymes coded by nuclear DNA  are synthesized upon cytoplasmic ribosomes  .The DNA codes are transcript into messenger RNA (mRNA) ( Ribonucleic acid ) molecules, which comes out of Nucleolus and translated protein synthesis by ribosomes attached to RER in the formof protein.

FUNCTIONS :  They are main site of protein synthesis  which is transported to ER.

PLASTIDS :  It is double membrane  ,discoidal structure, found mainly in  algae and plant cells , beside being discoidal /rhombic in plant cells they are present  in variable shape  like in the algae .They may be  Coiled  , Spiral  or ribbon shaped .They also have their own DNA  .They are of three types a) LEUCOPLAST :  They are white/ colorless  and found in non photosynthesis tissue of plants such as roots, bulb seeds , they change into other type of plastids  it’s primary function  is the storge of starch, oil , proteins b) CHROMOPLAST They are  coloured plastids except green , it imparts  colour to fruits and  flowers c) CHLOROPLAST ;  It contain chlorophyll  which  impart green colour to the leaves and found  in aerial parts of plants  it helps in the process  of photosynthesis so it is  also called Kitchen of the cell , It is of two type i) GRANA  which constitute lamellar system. these are founded  on the top of each other. These stacks are called  Grana . Each granum of the chloroplast is formed by superimposed closed  compartment called Thylakoids they are the site of light reaction of photosynthesis as they contain the photosynthetic pigment chlorophyll, photosynthetic units ii) STROMA : It is  granular transparent substance is called  matrix >  Grana are embedded in it, it also contain lipids  droplets, starch grains and ribosomes

VACUOLES  :  These are membrane bounded region in the cytoplasm contain water and other substances .It is bounded by single membrane called Tonoplast .In animals it is absent or of very small size In plants  there is single large vacuole is is found which occupies 90% of the volume of the cell  It’s main function that it helps in maintaining osmotic pressure in cell and stores toxic metabolic products/ wastes products, water , sugar and protein

LYSOSOMES / SUICIDAL BAGS  They are tiny single membrane bound cell organelle contains  powerful digestive enzymes for intercellular digestion  , It is absent in RBC  It is synthesis by Golgi bodies and  enzymes present in it and are synthesis by RER

FUNCTION  Their main function  is digestion, it means they break down  worn out cellparts,they are the kind of waste disposal system of the cell It also help the digesting the foreign material like viruses and bacteria invaded in cell .

SUICIDAL BAGS : During the disturbances  in cellular metabolism / cell damage Lysosomes burst and their enzymes are released into cytoplasm which digest the own cell therefore it is known as suicidal bag.

PLANT CELLS ; They contain chloroplast for  photosynthesis, It have a cell wall to maintain it’s structure and rigidity , usually do not have lysosome and peroxisomes, cells  are square and rigid /geometrical shape it has large central vacuoles

ANIMAL CELL ; It has chloroplast ,no cell wall , may contain cilia and  flagella , cells are fluidic and flexible in shape  it has very small or no vacuoles  but have lysosomes.

CELL DIVISION  :  New cells are formed  in the organism  to relace dead cell/ old cells/ order to grow/  injured cells and to form  gametes for reproduction . The process by which  new cells are made  is called division of cell. they are of two type a) MITOSIS It is the process of cell division by which  most  of the cells divide  for the growth is called mitosis. In tis process , each cell  called mother cell  divides to form two identical daughter cells. The daughter cells have the same number of chromosomes as the mother cell it helps in growth and repair of tissue in organism  b) MEIOSIS  In this specific cells of reproductive organs/ tissue in animals  and plant  divide to form gametes, which after fertilization give rise to offsprings . They divide by different process called meiosis which involve  two consecutive  divisions. When cell divides by  meiosis it produces four new cells  instead of two . The  new cells have only  half the number of chromosomes than that of mother cells and these new cells are transformed into gametes .

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