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The Fundamental Unit Of Life
• cell
Cell is the structural and functional unit of life
...
Since all living
organisms are formed of cells and their
physiological ,biochemical, genetic and metabolic activities
take place inside the cell, therefore ,it is called the basic
unit of life
...

• Robert brown later in 1831 discovered the nucleus of the
cell
• In 1839,Purkinje gave the term 'protoplasm' for the fluid
substance of the cell
...
This theory however
did not explain how new cells were formed
...
He
modified the hypothesis of Schleiden and Schwann to give
cell theory the final shape
...
All the living organisms are composed of and
product of cells
...
All the cells arise from the pre-existing cells
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Some of the examples which
shows variation in shapes are as follows:
▫ Bio- concave and round -Human Red Blood
Cells
▫ Amoeboid- White Blood Cells
▫ Narrow And Long -Columnar Epithelium
▫ Oval And Round -Mesophyll Cells

○ Number
All organisms are composed of cells
...
On the basis of
this ,organisms are classified into two types :

Unicellular
Organisms composed of single cells are called
Unicellular organisms
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Multicellular
Organisms like us are made up of many cells called
multicellular organisms
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All multicellular organisms
arise from single cells
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The lack nucleus sand other cell organelles
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g
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Some prokaryotes contain a region within
the cell called nucleoid where the genetic material is
freely suspended
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2 Eukaryotic cells

These are the well-developed cells
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These cells have well-developed membrane
bound organelles such as mitochondria , lysosome,
endoplasmic reticulum etc
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DIFFERENCE BETWEEN PROKARYOTIC CELL AND
EUKARYOTIC CELL

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ANIMAL CELL
Common features and general features :

The cytoplasm is the main arena of cellular
activities in animal cell
...

Animal cells have irregular shape due to the
absence of a cell wall
...
These
organelles carry out specific functions that are
needed for the normal functioning of the cell
...
They are the sites of protein
synthesis
...
It has
larger size than the animal cell
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There is presence of rigid cell wall which
is made up of cellulose , glycoproteins,
lignin ,pectin and hemicellulose
...
This thin membrane forms
the barrier between the cell's inner contents and the
intestinal fluid [the fluid that surround the cell]
...
Cilia ,flagella, and
microvilli are examples of modified plasma membrane
extensions
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It also
prevents the movement of some other materials
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Types of transport are given below:

1
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For instance ,exchange of
gases through stomata
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• Facilitated diffusion -It is the type of
diffusion in which material moves across a
membrane along a concentration
2 Osmosis: Osmosis is defined as the
spontaneous movement of solvent or water
molecules from the area of lower concentration
[diluted solution] to an area of higher
concentration through a selectively permeable
membrane
...
It could be
endosmosis or exosmosis
...

Endosmosis and Exosmosis process takes place on
the basis of the concentration gradient
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1
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Such a solution is known as an isotonic
solution
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The cell will stay the same size
...
e
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Such a solution is known
as Hypotonic Solution
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Such a solution is known as Hypertonic
Solution
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The plant cell wall is a non-living
rigid structure whereas the cell wall is absent in
animal cell
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 It provides mechanical support against gravity
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 Cell Wall prevents over expansion of cell
membrane when water enters the cell and
inhabits plant cell from excessive endosmosis
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Nucleus
The nucleus was discovered by Robert Brown in
1831
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➢ Functions of a Nucleus
 It controls all the metabolic activities of the
cell and regulates the cell cycle
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 Division of Nucleus is prerequisite to cell
division
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R
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It is
often termed as a system of the membrane
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These
organelles are also known as Dictyosomes
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Functions of Golgi Apparatus
• Its functions include the
storage ,modification and packaging of
secretary products in the vesicles
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•

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LYSOSOMES
These are the tiny sac like granules filled with
different types 0f digestive enzymes that help in
intracellular digestion
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Lysosomes are kind of waste disposal
system of the cell

➢ FUNCTIONS OF LYSOSOMES
• IT HELPS IN INTRACELLULAR
DIGESTION BECAUSE THEY CONTAIN
POWERFUL DIGESTIVE ENZYMES
CAPABLE OF BREAKING DOWN ALL
ORGANIC MATERIAL
• THEY HELP IN DIGESTING FOIREIGN
MATERIAL , OLDER CELLS AND WORN
OUT CELL ORGANELES

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VACUOLES
Vacuole is a membrane bound space found
in the cytoplasm
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It is bounded by a single
membrane called Tonoplast
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• Helps in osmoregulation in plant
cells ,i
...
,expels excess water from the
cell
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•

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PLASTIDS
Plastids are found in almost all plant cells
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It is the
largest cell organelle in the plant cell
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Chromoplast- These are yellow and red
colored ,fat soluble plastid
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➢ FUNCTIONS OF PLASTIDS
• Photosynthetic pigments of chloroplast traps

light energy of the sun and converts it into the
chemical energy in the form of glucose
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RIBOSOMES
Ribosomes are the granular structure first
observed under electron microscope by
George Palade
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➢ FUNCTIONS OF RIBOSOMES
• Synthesis of cellular protein is the main
function of the ribosome
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MITOCHONDRIA
It is a sausage shaped structure found in the
cytoplasm of all eukaryotic cells except
human RBCs
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ATP is known as the energy
currency of the cell
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Most of the oxidative
metabolism and ATP production occurs
in Mitochondria
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New Section 4 Page 16



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