This ppt contains information about THE FUNDAMENTAL UNIT OF LIFE that is cell.

1. THE
FUNDAMENTAL
UNIT OF LIFE

2. Q.WHAT IS CELL ?
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“ A cell is defined as the
smallest, basic unit of life
that is responsible for all of
life’s processes ”.
All organisms are made up of cells
.They mean be made up of a single
cell (unicellular) , or many cells
(multicellular)

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ROBERT HOOKE discovered the cell in
1665 .While examining a thin slice of cork
, Robert Hooke saw that the cork
resembled the structure of honeycomb
consisting of many little compartments.
However his compound microscope had
limited magnification, and hence , he
could not see any details in the structure.
Owning this limitation, Hooke concluded
that these were non – living entities.
Q.WHO DISCOVERED CELLS ?
The Fundamental Unit Of Life

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ANTONVAN LEEUWENHOEK
(1674) observed cells under
another compound microscope
with higher magnification. This
time, he had noted that the cells
exhibited some form of
movement (motility).
As a result Leeuwenhoek
concluded that these
microscopic entities were
“alive”.

5. In 1883, ROBERT BROWN a Scottish botanist
Provided the first insight into the cell structure.
He was able to describe the nucleus present in
the cells of orchards.
The cell theory, that all cells and that the cell
is the basic unit of life, was presented by two Robert Brown
biologists, Schleiden (1838) and Schwann
(1839) .
The cell theory was further expanded by Virchow (1855) by suggesting that all
cells arise from pre-existing cells .
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6. • TYPES OF CELL
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Cells are similar to the factories with different laborers and
departments that work towards common objective. Various
types of cells perform different functions. Based on cellular
structure, there are two types of cells.
•Prokaryotic cells
•Eukaryotes cells
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7. • PROKARYOTIC CELLS
Prokaryotic cells are single-celled microorganisms
known to be the earliest on earth . Prokaryotes
includes Bacteria and Archaea . The photosynthetic
prokaryotes include cyanobacteria that perform
photosynthesis.
Characteristics of Prokaryotic cells
1. They lack a nuclear membrane.
2. The genetic materials is present on a single chromosome.
3. The cell wall is made up of carbohydrates and amino acids.
4. The plasma membrane acts as the mitochondrial membrane carrying respiratory
enzymes.
5. Mitochondria, Golgi bodies, Chloroplast and Lysosomes are absent .
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8. • EUKARYOTIC CELLS
Eukaryotic cells have a nucleus enclosed within
the nuclear membrane and form large and
complex organisms . Protocol, fungi, plants,
and animals all have eukaryotic cells.
Characteristics of Eukaryotic cells
1. Eukaryotic cells have the nucleus enclosed within the nuclear membrane.
2. The cell has mitochondria.
3. A cell wall is the outermost layer of the Eukaryotic cells.
4. The cells divide by a process called mitosis.
5. Flagella and cilia are thr locomotory organs in a Eukaryotic cells .
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9. STRUCTURAL
ORGANISATION OF
A CELL
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10. • CELL MEMBRANE OR PLASMA MEMBRANE
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The cell membrane supports and protects the cell. It
controls the movement of substances in and out of
the cells. It separate the cell from the external
environment.The cell membrane present in all the
cells.
It also prevents movement of some other materials.
The cell membrane, therefore, is called a selective
permeable membrane.
Some substances like carbon dioxide or oxygen cam
move across the cell membrane by a process called
diffusion.
Water also obeys the law of diffusion.The movement
of water molecules through such a selective
permeable membrane is called osmosis.

11. • CELLWALL
The cell wall is the most prominent part of the
plant’s cell structure. It is made up of cellulose,
hermicellulose and pectin.
The cell wall is present exclusively in plant cells.
It protects the plasma membrane and other
cellular components. The cell wall is also the
outermost layer of plant cells.
It provides shape and support to the cells and
protects them from mechanical shocks and
injuries.
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12. • NUCLEUS
The nucleus contains the hereditary material of the
cell, the DNA.
The nucleus has a double layered covering called
NUCLEAR MEMBRANE. The nuclear membrane
has pores which alows the transfer of material from
inside the nucleus to its outside, that is to
Cytoplasm.
The nucleus contains Chromosomes, which are
visible as rod shaped structures only when the cell
is about yo divide. CHROMOSOMES contains
information for inheritances of features from
parents to next generation in form of DNA
molecules.
The nucleus plays a central role in
cellular reproduction, the process by
which a single cell divides and form
two bew cells. It also plays a crucial
part, along with the environment, in
determining the way the cell will
develop and what form it will exhibit at
maturity, by directing the chemical
activity of the cell.
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13. • CYTOPLASM
The fluid that fill up the cells is referred to as the CYTOPLASM.
It also contains specialised cell organelles. Each of the
organelles performs a specific function for the cell.
Cell organelles are enclosed by membranes. In
Prokaryotes, besides the absence of define nuclear region, the
membrane- bound cell organelles are also absent .
On the other hand, the
Eukaryotic cells have nuclear membrane as well as membrane-
enclosed organelles.
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14. CELL
ORGANELLES

15. 1. ENDOPLASMIC RECTICULUM (ER)
“Endoplasmic Recticulum is a complex
network of tubular membranes exclusively
present in the cytoplasm of the eukaryotic
cells”.
Endoplasmic Recticulum transpires in two
forms: a type with ribosome-studded surface
and another with a smooth surface.The latter
is called the Smooth endoplasmic
recticulum, and the former is called the
Rough endoplasmic recticulum.
Endoplasmic Recticulum

16. Rough Endoplasmic
Recticulum
• The Rough endoplasmic recticulum is
name so because of its appearance.
• It is a series of connected flattened sacs
having several ribosomes on its outer
surface, hence the name .
• It synthesizes and secrets proteins in
the liver,hormones and other
substances in the glands.
• Rough ER is prominent in cells where
proteins synthesis happens.
Smooth Endoplasmic
Recticulum
• The Smooth Endoplasmic Recticulum, on
the other hand, does not have ribosome.
• The Smooth Endoplasmic Recticulum has
a tubular form.
• Smooth Endoplasmic Recticulum
transports the products of thr Rough ER
to other cellular organelles, especially in
the Golgi Apparatus.
• Smooth Endoplasmic Recticulum is
responsible for the synthesis of essential
lipids such as phospholipds and
cholesterol.
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17. 2. GOLGI APPARATUS
The Golgi Apparatus has multiple names
such as Golgi complex or Golgi body. The
name is given on the scientist, who
discovered the organelles, i.e. Camillo
Golgi. It is found in all the eukaryotic cells,
plants as well as animals. Its main function
is the packaging and secretion of proteins .
It receives proteins from Endoplasmic
Recticulum. It packages it into membrane-
bound vesicles, which are then transported
to various destinations, such as lysosomes,
plasma membrane or secretion.
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18. 3. MITOCHONDRIA
“Mitochondria are membrane-bound
organelles present in the cytoplasm of
all eukaryotic cells, that produce
adenosine triphosphate (ATP),the main
energy molecule used by the cell”.
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Mitochondria popularly known as the
“power house of the cells“,
Mitochondria are a double membrane-
bound organelle found in most
eukaryotic organisms . They are found
inside the cytoplasm and essentially
functions as the cell’s “digestive system”.
They plays an important role in breaking
down nutrients and generating energy-
rich molecules for the cell.

19. 4. LYSOSOMES
Lysosomes are a kind of waste disposal system of
the cells. Lysosomes help to keep the cell clean by
digesting any foreign material as well as worn out
cell organelles. Foreign materials entering the cell,
such as bacteria or food, as well as old organelles
end up in the Lysosomes, which breaks them up
into small pieces. Lysosomes are able to do this
because they contains powerful digestive enzymes
capable of breaking down all organic material.
During the disturbance in cellular metabolism, for
example, when the cell gets damaged, Lysosomes
may burst and the enzymes digest their own cell.
Therefore, Lysosomes are also known as the
“Suicide bags” of the cell.
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20. 5. PLASTIDS
Plastids are present only in plants cells . There
are two types of plastids – Chromoplasts (colored
plastids) and leucoplasts (white or colourless
plastids). Plastids containing pigment chlorophyll
are known as chloroplasts. Chloroplasts are
important for photosynthesis in plants.
Chloroplasts also tain various yellow or orange
pigment in addition to chlorophyll. Leucoplasts
are primarily organelles in which materials such
as starch, oils and proteins granules are stored.
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21. 6. VACUOLES
• Vacuoles are storage sacs for solids or liquid contents. Vacuoles are
small sized in animals cells while plants elks have very large Vacuoles.
The central Vacuoles of some plants cells may occupy 50-90% of the cell
volume.
• In plants Vacuoles are full of cell sap and provide turgidity and rigidity to
the cells. Many substances of importance in the life of the plant cells are
stored in Vacuoles.
• In some unicellular organisms, specialized Vacuoles also plays
importance role in expelling excess water and some wastes from the
cell .
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Shiv kumar
Class – IX’E’
ROLL - 35