Skip to main content

CELL

Cell

It is the structural , functional and  biological unit of life. Cell is smallest unit of life. And cell also called building  blocks of life 

  • Cell is termed as the structural unit of life as it provides structure to our body.
  • Cell is considered as the functional unit of life as all the functions of the body take place at cell level.

Discovery of cell:

  • Discovered by Robert Hooke in 1665.
  • Robert Brown in 1831 discovered the nucleus in the cell.

Cell Theory:

Cell theory states that:

  • All living organisms are composed of cells.
  • Cell is the fundamental unit of life.
  • All new cells come from pre-existing cells

  • Types of Organisms on the Basis of Number of Cells
    There are two kinds of organisms on the basis of cells:
    (i) Unicellular Organisms: The organisms that are made up of single cell and may constitute a whole organism, are named as unicellular organisms.

  • For example: Amoeba, Paramecium, bacteria, etc.

    (ii) Multicellular Organisms: The organisms which are composed of a collection of cells that assume function in a coordinated manner, with different cells specialized to perform particular tasks in the body, are named as multicellular organisms.

    For example: Plants, human beings, animals, etc.

    Shape and Size of Cells

    • Cells vary in shape and size. They may be oval, spherical, rectangular, spindle shaped, or totally irregular like the nerve cell.
    • The size of cell also varies in different organisms. Most of the cells are microscopic in size like red blood cells (RBC) while some cells are fairly large like nerve cells.

    Types of Cells
    The cells can be categorized in two types:
    1. Prokaryotic Cell  2. Eukaryotic Cell

  • 1. Prokaryotic cell
    Prokaryotic cells are cells in which true nucleus is absent. They are primitive and incomplete cells. Prokaryotes are always unicellular organisms. For example, archaebacteria, bacteria, blue green algae are all prokaryotes.   

                                                                                          2. Eukaryotic Cell. 

  • Eukaryobc cells are the cells in which true nucleus is present. They are advanced and complete cells. Eukaryotes include all living organisms (both unicellular and multicellular organisms) except bactera and blue green algae.          

Difference Between Prokaryotic and Eukaryotic Cells:

S. No.

Prokaryotic cell

Eukaryotic cell

1.

Size of cell is generally small (1-10 mm).

Size of cell is generally large (5-100 mm).

2.

Nucleus is absent.

Nucleus is present.

3.

It contains single chromosome.

It contains more than one chromosome.

4.

Nucleolus is absent.

Nucleolus is present.

5.

Memrane bound cell organelles are absent.

Memrane bound cell organelles such as mitochondria, plastids, endoplasmic reticulum, golgi apparatus, lysosomes, etc., are present.

6.

Cell division takes place by fission or budding.

Cell division takes place by mitotic or meiotic cell division.


Comments

Post a Comment

Popular posts from this blog

Heisenberg's Uncertainty Principle

Introduction Werner   Heisenberg   a German physicist  in 1927 stated uncertainty principle which is the consequence of dual behaviour of matter and radiation. It states that it is impossible to determine simulataneously, the exact position and exact momentum( or velocity) of an electron. Heisenberg's Uncertainty Principle states that there is inherent uncertainty in the act of measuring a variable of a particle. Commonly applied to the position and momentum of a particle, the principle states that the more precisely the position is known the more uncertain.  the momentum is and vice versa. This is contrary to classical Newtonian physics which holds all   variables of particles to be   measurable to an arbitrary uncertainty given good enough equipment. The Heisenberg Uncertainty Principle is a fundamental theory in quantum mechanics that defines why a scientist cannot measure multiple quantum variables simultaneously. Until the dawn of quantum me...
Post a Comment
Read more

CARBON AND ITS COMPOUNDS (PART-2)

  Homologous Series:   Series of organic compounds having the same functional group and chemical properties and successive members differ by a CH 2   unit or 14 mass units are known as Homologous series. Homologous series of Alkanes, Alkenes and Alkynes Characteristic of Homologous Series The successive members in homologous series differ by CH 2  unit or 14 mass unit. Members of given homologous series have the same functional group. All the members of homologous series shows similar chemical properties. Functional Group:   An atom or group of atoms present in a molecule which largely determines its chemical properties are called Functional Group. Nomenclature of Organic Compounds:   It is difficult to remember millions of compounds by their individual common name. Thus, to systematize the nomenclature of organic compounds IUPAC (International Union of Pure and Applied Chemistry) has given certain rule which is as follows: 1. Identify the Number of Carbon ...
13 comments
Read more