Cells are the fundamental units of life, first discovered by Robert Hooke in 1665. All living organisms consist of one or more cells, which can be unicellular or multicellular, and they possess various structures such as the nucleus and cytoplasm. Key components like the cell wall, cell membrane, and organelles support cell functions, while processes such as cell division create new cells for growth and replacement.

2. Cells are the basic
structural units and the
building blocks of all living
organisms.
Example- Amoeba , Cheek
Cells , etc .

4.  Discovery of the Cell- Cell was
discovered by Robert Hooke in 1665
after observing a piece of cork under
a magnifying device.
 Robert Hooke coined the term “cell”.
 Schleiden and Schwann proposed the
cell theory. According to cell theory.
1. Cells are the basic structural and
functional units of life.
2. All living organisms are made up of
one or more cells.
3. New cells arise from pre-existing

5. Cells that are made up of single
cell are called Unicellular organisms
.
Example – Amoeba , Paramecium .
Cells that are made up of multi
cells are called multicellular
organisms.
Example – Humans , Plants ,

6. animals
amoeba
paramecium
plants

7. Most of the cells have a definite shape.
 Some cells such as that in Amoeba have
no definite shape.
The human red blood cell (RBC) is
spherical-shaped.
 The muscle cells in humans are spindle-
shaped.
 The human nerve cells have elongated
branched structure.
 In plants and bacteria, the cell is
enclosed in a protective covering called cell
wall, which gives shape and rigidity to the
cells.

8. An ostrich egg measures 170m * 130m.
It is the largest single cell .
Bacteria is the smallest cell is
0.0001mm * 0.0005mm . It is the
smallest cell .
Human red blood cells are 0.007mm in
diameter .
A typical cell is about 0.02mm in
diameter . It can only seen through a
powerful microscope .

9. A typical cell
Red blood cells
Bacteria
An ostrich egg

10. The components of cell are:-
1. Cytoplasm
2.Cell wall
3.Cell membrane
4.Nucleus
And some other organelles

11. The cytoplasm is a jelly - like
substance that makes up most
of the inside of a cell . All life
functions take place in the
cytoplasm ( kytos means
hollow plasma means liquid )

12. Cell wall is present in Plant
cells but absent in animal cells
.
Cell wall supports and
protects the plant cell since
plants do not have skeletons
for support .

13. It is a thin covering that surrounds
cytoplasm .
It is also called the plasma
membrane.
It protects the cell and gives it a
shape .
However it allows minerals , water
and some other necessary
substances to pass through it .

14. It is the control centre of the cell .
The liquid in the nucleus is called nucleoplasm .
The thin nuclear membrane is porous and
allows the movement between the cytoplasm
and the nucleus .
Inside nucleus there are thread like
structures called chromosomes . These carry
jenes that carry information of cells .
The cytoplasm and the nucleus together make
protoplasm. It is the living substance of the
cell .

15. Organelles are the small structures present in
the cytoplasm .some of these are :-
1. Mitochondria - They are power house of the
cell.
2. Vacuoles – They are sac like structures . They
store food , water and other wastes .
3. Golgi bodies – They secrete enzymes .
4. Endoplasmic reticulum – These helps to
transport substances within the cell .
5. Lysosomes– They help to destroy old

16. 1. They have
proper nucleus
.
2. Example –
humans , plants
, protozoa , etc
.
1. They don’t
have proper
nucleus .
2. Example –
bacteria , etc .

17. 1.It has cell wall
.
2.It has large
vacuoles .
3.It has
chlorophyll .
1.It does not
have cell wall .
2.It has small
vacuoles .
3.It does not
have
chlorophyll .

19. The process by which new cells
form is called cell division .
The new cells are called daughter
cells .
New cells are needed for the
growth of an organism and to
replace cells that die .