Introduction to Cell

Question 1

What is a cell?

Answer 1

cell is the
fundamental structural and functional unit of all living organisms

Question 2

Unicellular organism are capable of?

Answer 2

Unicellular organisms are capable of
(i) independent existence and
(ii) performing the essential functions of life.
-Anything less than a complete
structure of a cell does not ensure independent living.

Question 3

What is Cell Theory, Explain about its genesis?

Answer 3

In 1838, Matthias Schleiden, a German botanist,
-examined a large number
of plants and observed that all plants are composed of different kinds of
cells which form the tissues of the plant.

-At about the same time, Theodore
Schwann (1839), a British Zoologist, studied different types of animal cells
and reported that cells had a thin outer layer which is today known as the
‘plasma membrane’.

-He also concluded, based on his studies on plant
tissues, that the presence of cell wall is a unique character of the plant
cells.

-On the basis of this, Schwann proposed the hypothesis that the bodies
of animals and plants are composed of cells and products of cells.

-Schleiden and Schwann together formulated the cell theory. This theory
however, did not explain as to how new cells were formed.

-Rudolf Virchow
explained that cells divided and new cells are formed from
pre-existing cells (Omnis cellula-e cellula).

-He modified the hypothesis of
Schleiden and Schwann to give the cell theory a final shape.

• Cell theory
  as understood today is:
  (i) all living organisms are composed of cells and products of cells.
  (ii) all cells arise from pre-existing cells.
  (iii) omnis cellula - e - cellula