Cell Introduction, Functions and Types

Cell Introduction, Functions and Types

Introduction: – 

The cell is the structural and functional unit of life. All living organisms are made by the cell. Cytology– Study of cell structure and function. The word coined by Hertwig
Robert Hooke- Father of cytology.
Cell Discovered by– Robert Hooke saw the dead cell in cork. A. V. Leeuwenhoek first saw living cell.

During evolution first It is produced by the abiotic process or chemical synthesis

Cell Theory

It is proposed by Malthias Schleiden and Theodore Schwann. according to this theory, the cell is the functional, structural and hereditary unit of life.
Rudolf Virchow said Omnis cellula e-cellula means new cells are formed from pre-existing cells.
The final cell theory is –
(A) All living organisms are composed of cells and component of cells.
(B) All cell arise from pre-existing cells.

Exception of This Theory:-

(I) Virus:- Acellular, only made by nucleic acid and protein
(II) Viroids:- They have RNA particle only.
(III) Virions:- They are an inactive carrier of the viral genome.
(IV) Prions:- Only made by protein do not have a nucleus.
(V) RBC- do not contain Nucleus (camel’s RBC contains nucleus)
(VI) Multinucleate organisms:- Syncytium in the animal, Coenocyte in plants, Plasmodia in slime molds.
(VI) B and T Lymphocyte- have nonidentical genetic material.


Mycoplasma:- smallest cell, 0.3 micrometers in length
Bacteria:- 3-5 micrometer in length
Human RBC:- 7micrometer
Nerve cell:- Longest cell, 90cm in length
Bohemia Nivea:- Longest plant cell
Acetabularia:- Longest unicellular plant
Ostrich Egg- Largest single cell


They may be disc-like, polygonal, columnar, cuboid, the thread like or even irregular

(adsbygoogle = window.adsbygoogle || []).push({});


On the basis of evolution and structure of nucleus C. B. Van Neil classify cells into two classes.

Prokaryotic cell:

Pro -> Initial (Primitive), Karyon -> Nucleus

  • Bacteria, Blue-green algae, Mycoplasma (absence of cell walls), PPLO (organisms such as Pleuro pneumonia) etc. have prokaryotic cells.
  • The nucleus naked primitive called the Nucleoid, which lacks the histone protein.
  • Membrane-bounded organelles are absent
  • The outer layer of prokaryotes is the glycocalyx that is made of polysaccharide which is in the form of a hard shell (Capsule CAPSULE) or soft coat (SLIME LAYER).
  • The cell wall is made of peptidoglycans.
  • The plasma membrane is made of fat, proteins, and oligosaccharides.
  • Bacteria are of G + VE and Gram -VE type.
  • MESOSOME is formed from the interaction of the plasma membrane. On which enzymes for respiration are present.
  • Contain extra genomic, single circular DNA called plasmid.
  • The bacterial cells that are motile or non-motile.
  •  FLAGELLUM – There are three parts of flagellum –
  • Filament hook and basal body ·
  • PILI, FIMBRIAE – does not play a role in mobility. But it helps in an adhesive.
  • Ribosome 15-20nm, the 50s and 30s divided into 2 sub-units – total 70s –
  • Ribosomes help in protein synthesis. Known as the factory of protein.
  •  RNA + Ribosome -> Polyribosome or POLYSOMES
  • Inclusion Bodies:- Contain phosphate granules, cynopycean granles, glycogen granules, polyhyderoxybutret granules, sulfur granules, carboxysomes and gas juices.
  • They divide by amitosis.

Eukaryotic cell:-

  • Eu- well, Karyon- nucleus. They have a well-developed nucleus.
  • They contain one or more nucleus.
  • Their genetic material is organized into the chromosome.
  • they contain membrane-bounded organisms.
  • All plants, animals, fungi, protists contain eukaryotic cells. Plant cell and animal cells are also different.
  • They have 80s ribosome.
  • they divide by mitosis.


Cell Introduction, Functions and Types

For eBook

BSER books
NCERT books
Molecular Biology of the Cell-Alberts
Cell and Molecular Biology Concepts and Experiments.Gerald Karp
Cell Biology, Genetics, Molecular Biology, Evolution and Ecology by Verma, Agarwal

1 Comment

Leave a reply

Shopping cart