The Fundamental Unit of Life

                                     THE FUNDAMENTAL UNIT OF LIFE 

All organisms including plants and animal are composed of cell. Each and every cell arises from pre - existing cell . These cells are become specialized to perform different specialized functions after division. Cell is the basic fundamental structural and functional unit of living organisms . 

Discovery of cell -  

ROBERT HOOKE ( 1665 ) EXAMINED A THIN SLICE OF CORK UNDER THE PRIMITIVE MICROSCOPE . HE OBSERVED THAT CORK CONSISTS of small box - like structures resembling honeycomb . He called these boxes cells 

                                                

Scientist                     Year                                                   Work 

Robert Hooke          1665                     Discovered cells for first time in cork slice with the help of

                                                                  a primitive microscope 

Leeuwenhoek            1674                       discovered free living cells in pond water using an                                                                                    improved   microscope 

Robert brown              1831                     Discovered nucleus in cell 

Purkinje                       1839                      Coined the term "protoplasm " for the fluid substance                                                                           of cell 

___________________________________________________________________________________

________________________________________________________________________________

Shape of cell - some cell have fixed cell ( e.g. most plant and animal cells ) , while some cells like WBSs and amoeba keep changing their shapes . Fixed shaped cells may be of various types like elliptical(e.x.  fat cell), spherical (e.g. ovum)spindle - shaped ( e.g. smooth muscle cell ) knobbed thread ( e.g. sperm ) , discoidal ( e.g. RBC), elongated (e.g. nerve cell ) , etc.    

Size of cells - 

                                   The size of cell varies significantly from the smallest cell of mycoplasma ( 0.1-0.5 um ) to very large egg cells of the ostrich (, 18 cm ) . Longest cells of human body are the nerve cells , which may reach up to a length of 90 cm . 

Some Important Questions 

1- who discovered free-living cells ? 

2-Give name of two organisms each that are ? B- Unicellular                       B- Multicellular

3-Name the two cells which can change their shape 

4- Which is the longest cell in human body ? 

5- Unicellular organisms organisms differ from multicellular ones . how ? 

cell membrane / plasma membrane 

This is outermost living , thin and delicate covering of cell . it separates the contents of the cell from its external environment . 

presence of lipids and proteins ( as phospholipids) provides  flexibility to plasma membrane . It enables engulf food and other material from external environment . This process is called endocytosis, e.g. Amoeba acquires food through this process , with the help of finger - like projections called pseudopodia.       __________________________________________________________________________________

      

. 

 __________________________________________________________________________________ 

 __________________________________________________________________________________

                                        Prokaryotic cell 

1- size- Generally small ( 1-10 um) 1um = 10m 

2- Nuclear region - Undefined and contains only nucleic acids called nucleoid , lacks nuclear membrane . 

3- Chromosome are single 

4- membrane bound cell organelles absent 

 __________________________________________________________________________________

                                                   Eukaryotic cell 

1- Size - Generally large ( 5-100 um ) 1um-10m 

1-Nuclear region - Well defined and surrounded by a nuclear membrane 

3- Chromosome are more than one 

4- membrane bound cell organelles present 

__________________________________________________________________________________

        Cell wall -

1-They are determine the morphology , growth and development of plant cell 

2-Protect the protoplasm                                     

3-Help the plant in with standing the gravitational forces 

4- Transport of material and metabolites into and out of the cell 

5- They with the turgor pressure 

CELL - CELL MEMBRANE , CYTOPLASM , NUCELUS 

                                                            ⇩

                                    CELL ORGANNELS , CELL INCLUSIONS 

Cell organelles - Endoplasmic Reticulum 

                           - Mitochondria  

                            - Golgi apparats 

                              - Ribosomes 

                              - Lysosomes 

                              -    plastids 

__________________________________________________________________________________

Cell inclusions - 

                                     -  Granules 
                                     - Vacuoles

__________________________________________________________________________________

Nucleus - 

              - nuclease membrane 
              - nucleoplasm 
              - nucleolus 
              - chromatin fibers  

__________________________________________________________________________________

                                           Animal cell 

Nucleus - 

Structure - ( 1) - Largest cell organelle coloured  with double layered nuclei membrane 

2- Mostly spherical , dense and contain jelly like fluid called Nucleoplasm . 

3- Contain network of thread like structure called cramative fiber Which contain DNA ( Dioxayribo nuclic acid ) 

4- Play key role of cellular Reproduction . 

__________________________________________________________________________________

                                                         

                          Endoplasmic Reticulum 

__________________________________________________________________________________

  Function - Make and package proteins and lipids 

. Found in eukaryotic cell 

. Longest organelle 

. Two type - RER and SER 

RER- ribosomes are attendance to its outer surface hence it surface appear rough 

SER- lipid formation detarofication  in verification liver cell 

__________________________________________________________________________________

                                                         

Golgi apparatuses  - 

__________________________________________________________________________________

           THANK  
                                 YOU 

__________________________________________________________________________________