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BIOLOGY
HOLIDAY
HOME
WORKTHE FUNDAMENTAL
UNIT OF LIFE
In 1665 Robert Hooke examined the slice of
cork by self designed microscope .
Cork is a substance which comes from bark of
tree.
By microscope cork resembled the structure
of a honey comb consisting of many little
compartments.
This was very important invention in the history
of science that living things appear to consist
of separate small units.
The word cell use to describe this unit in
biology .
HISTORY
In1839 Purkinje discovered some fluid
substance in the cell termed protoplasm.
In 1940 with the discovery of electron
microscope complex structure of cell and
various organelles could understand.
CELL All organisms around us are made up of cells.
Some organisms are made up of single cell called
unicellular organism .e.g. Amoeba.
Many cells grouped together in a single body and
perform various functions called multicellular
organisms .
Some organisms have different kinds of cells with
different shape and size.
Each living cell has a capacity to perform certain
basic function . That are characteristics of all living
forms .
All living cell perform this basic function.
As we know there is a division of labour in
multicellular organism such as human being ,
means different part of our body perform different
part of our body perform different functions .
A single cell also perform different functions with
the help of its component which is known as cell
organelles .
These organelles together constitute the basic unit
called the cell.
STRUCTURE OF A CELLA cell have 3 features –
Plasma membrane
Nucleus
Cytoplasm
Plasma membraneCell membrane is the outer most covering of the cell
that separate the content of the from its external
environment .Structure The plasma membrane is flexible made up of
organic molecules –
Lipid
Protein
We can observe the structure of plasma only
through an electron microscope .
The flexibility of cell membrane also enable the cell
to engulf the food and other material from its
external environment . This process is known as
endocytosis. Ex :- Amoeba enquires its food through
this process.
Cell wall In plants cells addition to the plasma membrane
another rigid outer covering called the cell wall.
Structure
This is made up of complex substance cellulose .
It provide strength to plant.
Functions Cell walls permit the cell of plant , fungi and
bacteria to with stand very dilute external media
without bursting .
It take water by osmosis.
Function of plasma membrane Separation of content of cell.
Permit the entry and exit of material .
Prevent movement of some other material called
selectively permeable membrane .
Some substance like carbon dioxide , oxygen can
move across the cell membrane by a process
called diffusion. In diffusion substance move from a
region of high concentration to low concentration.
Use of diffusion – waste product can excrete out by
the cell like carbon dioxide , Respiration.
Movement of water through semi permeable
membrane is called osmosis.
Use of osmosis –
Transportation of water
Transportation of dissolve substance
Transportation of nutritious substance
Transportation/excretion of waste product
Examples of osmosis – unicellular fresh water organism
and most plant cell absorb water by plant root.
Use of diffusion – waste product can excrete out by
the cell like carbon dioxide , Respiration.
Movement of water through semi permeable
membrane is called osmosis.
Use of osmosis –
Transportation of water
Transportation of dissolve substance
Transportation of nutritious substance
Transportation/excretion of waste product
Examples of osmosis – unicellular fresh water organism
and most plant cell absorb water by plant root.
NUCLEUSNucleus is a darkly coloured spherical or oval
dot like structure near the Centre of each cell.
StructureDouble layer covering of nucleus – Nuclear
membrane.
Functions of nuclear membrane – porous and
transfer the material from nucleus to cytoplasm.
Chromosomes are rod shapely structure.
Parts of chromosomes – DNA and protein.
DNA – genes and chromatin .
Function of Nucleus – cellular reproduction
Types of nucleus –
Organisms with poorly defined nuclear membrane
is known as prokaryotes .
Organisms with well defined nuclear membrane is
known as eukaryotes.
NUCLEUS
Nucleus
chromosome
DNA
Genes Chromatin
Protein
Nuclear Membrane
CYTOPLASM The cytoplasm is the fluid content inside the plasma
membrane. It contains many specialized cell organelles .
CELL ORGNELLES Large and complex cells of multicellular organism
need a lot of chemical activities to support their complicated structure and functions.
To perform these activities membrane bounded little structures are present called organelles, this is the feature of eukaryotic cell
These organelles are visible only with electron microscope.
TYPES OF CELL
PROKARYOTIC CELL
Size:generally small
Nuclear region :poorly defined, nuclear membrane is absent.
Chromosome : single
Membrane-bounded cell organelles absent .
EUKARYOTIC CELL
Size:generally large
Nuclear region :well defined , nuclear membrane is present.
Chromosomes : more than one.
Membrane-bounded cell organelles present.
These organelles are :
1. Endoplasmic reticulum
2. Golgi apparatus
3. Lysosomes
4. Mitochondria
5. Plastids
6. Vacuoles
ENDOPLASMIC RETICULUM (ER) It is a large network of membrane bound tubes and
sheets.
Structure Long tubules and round or oval vesicles.
Type Rough Endoplasmic Reticulum (RER)
Looking rough under microscope because it contains
particles called ribosomes attached to its surface.
Ribosomes : sight of protein manufacturer
depending on need.
Smooth Endoplasmic Reticulum (SER)
Size of SER – Varies in size
Smooth in different cells and forms network system.
Functions Of Endoplasmic Reticulum Transport of material like protein within the cell
organs .
Providing a surface framework for some
biochemical activities of cell.
Detoxifying many poison and drugs .
GOLGI APPARATUS It was discovered by Camilo Golgi by his name is
called Golgi Apparatus .
Structure Membrane bounded vesicles arrange
approximately parallel to each other called cistern.
It is also connected with the membrane of ER so its
also complex cellular membrane system.
Functions Storage
Modifications
Packaging of products in vesicles
Formation of lysosomes
LYSOSOMES It is known as waste disposal system of the cell .
Helps to keep the cell clean by digesting any
foreign material like bacteria or food.
It contains powerful digestive enzymes which help
to digest foreign materials .
It is also known as suicide bags of a cell.
Structure Membrane bound sacs, filled with objective
enzymes.
MITOCHONDRIA Mitochondria are known as power house of the
cell.
It release energy for various chemical activities.
Structure It have 2 membrane covering outer membrane
is very porous while inner one is deeply folded .
These folds create a large surface area for
formation of ATP.
Functions ATP is Adenosine triphosphate .
It produce energy so it is known as the energy
currency of the cell.
It is a organelle of sense because it produce DNA
PLASTIDS Plastids are present only in plant cells.
Types Chromoplast – coloured plastids–green , yellow etc.
Leucoplast – white or colourless plastids .
Structure The internal organization of the plastids consist of
numerous membrane layers embedded in a
material called the stroma.
Functions It contains pigment chlorophyll known as
chromoplast and leucoplast .
Chloroplast contain pigment chlorophyll used for
photosynthesis , it is found in the chromoplast.
Leucoplast is used for storage.
Plastids work like mitochondria because its own
DNA and Ribosomes
VACUOLES Vacuoles are storage sac for solid or liquid
contents.
In plant cells there is very large central
vacuole , providing rigidity to cell.
CONCLUSION Cells have a basic structural organization with the
help of membrane and organelles.
Cells perform functions like respiration, obtaining
nutrition, forming new proteins and cleaning of
waste materials etc.
Thus cell is the fundamental structural and
functional unit of life.
PRESENTED BY –
Paridhi Gouri Patel
CLASS – 9th