(IGP) GS Paper 1 – General Science – “Cell”

Integrated Guidance Programme of General Studies for IAS
(Pre) – 2013

Subject – General Science
Chapter : Cell


Cells are small compart-ments that hold all of the biolo-gical equipments
necessary to keep organisms. Cells carry out all the basic functions of life:
growth, metabolism and reproduction.

Cell Theory

The term cell was coined by Robert Hooke in 1665. In 1838 matthias schleiden,
German botanist proposed the idea that all plants consists of cells. In 1839,
The Eodor Schwann a German zoologist asserted that all plant and animals are
made up of cells. This finding forms the basis of cell theory.

Components of Cell

  • In the living organisms there are two types of cellular

  • If we look at very simple organisms like bacteria and
    blue-green algae, We will discover cells that have no defined nucleus, these
    are prokaryotes cells.

  • The cells which have definite nucleus are known as

Cell membranes :

It is like a plastic bag with some tiny holes that bag holds
all of the cell pieces and fluids inside the cell and keeps foreign particles
outside the cell. The holes are there to let some things move in and out of the
cell. Compounds called proteins and phospholipids make up most of the cell
membranes the phospholipids make the basic bag.

Cytoplasm :

It is the fluid that fills a cell. Scientists used to call
the fluid proto plasm.cytoplasm contain many specialized cell called organ
cells. Each of these organ cells performs a specific function for the cell.

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Cell organells :

Organells are living part of the cell have definite shape,
structure and functions. To keep their function different from each other these
organelles use membranes bound little structure with in them selves. Some of the
important organells are :

  • Endoplasmic reticulum : It is a network of
    tulsular membranes connected at one end to the nucleus and on the other to
    the plasma membranes.

  • Ribosomes : It synthesis protein, and ER sent
    these protein in various part of the cell. Where as SER helps in the
    manufacture of fats.

  • Golgi apparatus : it is found in most cell. It is
    another packaging organelle like the endoplasmic reticulum. It gathers
    simple molecules and combines them to make molecules that are more complex.

  • Lysosomes : It is a kind of waste disposal system
    of the cell. It helps to keep the cell clean by digesting any foreign

  • Mitochondria : It is known as the power house of
    the cell. The energy required for various chemical activities headed for
    life is released by mitochondria in the form of ATP
    (adenosine-tri-phosphate) molecules.

  • Centrioles : It is a micro-tubular structure;
    centrioles are concerned with cell division. It initiates cell division.

  • Plastids : These are present only in plant cells.
    There are two types of plastids:-chromoplastes (colour plastides) and
    leucoplast (white or colourless plastids)

Some important facts regarding cells:

  • Nerve cells in animals are the longest cells.
  • Smallest human cell is red blood cell.
  • Largest human cell is female ovum.
  • The single largest cell in the world is of an ostrich.
  • The smallest cells are those of the mycoplasma.
  • Every minute about 3 millions cells in our body die.
  • Sieve tube in plants and the mature mammalian red blood cells do not
    have a nucleus.
  • The red blood cell carries respiratory gases.

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