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CELL – BASIC UNIT OF LIFE
Fundament unit of life
CELL – BASIC UNIT OF LIFE
Prokaryotic and Eukaryotic Cells
Multicellular Organisms
Cell Membrane and Cell Wall
Cell Organelles• Chloroplast• Mitochondria• Vacuoles• Endoplasmic Reticulum• Golgi Apparatus• Nucleus
Chromosomes • Basic Structure, Number
DISCOVERY OF CELL
In 1665 Robert Hooke – an English Scientist, Saw
Cells in a thin slice of cork with his crude
microscope.
He observed as “Honey – comb” like Structure
and named them as CELLULAE or CELLS
His discovery indicated for the first time that
living organisms consisted of number of small
structures or units.
Microscope
1665- Robert Hook discovery of cell
1674-A. Van Leeuwenhoek-studied living for the first
time.
1831-Robert Brown discovery and named Nucleus in a
cell
1838-39-M.J.Schleiden & Schwann formulated Cell
Theory
1855-Rudolf Virchow, Stated “Omnis cellula-e-cellula”
TO KNOW THE HISTORY OF CELL?
Robert Hook
Leeuwenhoek
Robert Brown
M.J.Schleiden
Schwann
Rudolf Virchow
Just as a building is made up of bricks the body of all
living organisms made up of cells.
Basing on the cellular organization some organisms are
made of single cells “Unicellular Organisms” e.g.
Chlamydomonas, Amoeba, Paramecium
Organisms which are made up of more than a cell
“multicellular”
Irrespective of unicellular or multicellular organisms
the cells perform similar basic functions for their
survival.
WHAT ARE LIVING ORGANISMS MADE UP
OF?
Cells are too small to be seen by necked eye.
They are studied with the help of microscopes.
Microscopes are high resolution instruments that
are used for observing fine details of very small
objects
Two common types of microscopes• Light microscope-magnification range from 100-1500• Electron microscope- magnification range from 1 lakh-
5 lakhs
GADGETS TO STUDY CELLS
Shape and size of cells vary but all of these are
ultimately determined by the specific function.
Shape and Size of cells
Some cell can change their
shapes amoeba, WBC but plants
and animals have almost fixed
shapes.
Smallest ell=
PPLO(mycoplasma)
Largest Cell-Ostrich egg
Longest animal cell-Nerve cell
A micrometer (μm) or micron is
one thousandth of a millimeter.
The Scale of Life
Unicellular
Made of Single Cell
Single cell able to
perform all the life
processes like obtaining
food, respiration,
excretion, growth and
reproduction.
Cannot be divided in to
cells, they are also called
acellular organisms
Amoeba, paramecium
UNICELLULAR VS. MULTICELLULAR
Multicellular
Made up of many number of
cells
Cells have a similar basic
structure and similar basic
life activities
Different shapes and
aggregated to form different
tissues
Tissues form organs and
organs give rise to organ
system that perform special
function.
Plants, Animals and Fungi
It performs all life function like intake of food
materials, excretion, metabolism, respiration,
irritability, etc.,
Division of Labour – Cell usually possesses a
number of components called cell organelles.
Each cell organelle performs different functions• Clearing waste material• Protein synthesis• Lipid synthesis
Cell is basic unit of life
A cell is a tiny mass of protoplasm which is
surrounded by a membrane and is capable of
performing all function of life.
A typical cell is formed of three parts• Plasma membrane-to create separate
environment • Nucleus-for its control• Cytoplasm-possessing metabolic machinery
What is Cell made up of?
The outer most delicate elastic membranous covering of the
cell that separates its contents from the external
environment is called Plasma Membrane
Plasma Membrane is Selectively Permeable (it allows entry
of certain substance restricting others)
It is made up of a bi-lipid layer and proteins are integrated
in out and inside.
Small carbohydrates are attached at placed to outer surface
of lipids and proteins.
Functions- Shape to contents of cell, Mechanical Barrier,
Semi-Permeable, Endocytosis, Recognition Centres, Flow of
Information, Osmosis, Cell Continuity, Modified to perform
special functions like absorption in microvilli.
Plasma Membrane-Cell Membrane
Plasma Membrane
Plasma membrane
SEM-Plasma membrane
Membranes act as physical
barriers between the organelles
of a cell and its cytoplasm and its
surrounding environment.
Impermeable – substances do not
pass through the membrane
Permeable – both solute and
solvent can pass through
Semipermeable – membrane
permeable to solvent but prevents
solutes passage
Selectively Permeable – if
membrane allows the passage of
solvent and some selected
solutes.
Transport Across the Membrane
Substances may pass across the membrane without or
with expenditure of energy-
Active Transport - substances pass the membrane with
consuming ATP
Passive Transport-substances pass the membrane
without consuming ATP
Bulk Transport – Large amounts of substances and food
particles across the plasma membrane
The process of bringing the bulk of materials from outside
by formation of endosomes is called endocytosis.
Bulk expulsion of materials as in secretion and excretion
is called exocytosis.
Active & Passive Transport
Active Transport
Passive Transport is of two types• Diffusion• Osmosis
Diffusion – The process of movement of substances
(solid, Liquid or Gas)from the region of higher
concentration to the region of its lower concentration
till spread uniformly in the given space is called
diffusion.
Passive Transport
Diffusion – Demonstration
Helps in spread of different
substances throughout
cytoplasm of cell.
Osmosis is a type of diffusion
where only solvent is allowed
to diffuse.
Diffusion helps in exchange
of respiratory gases between
the cells and their
environment.
Transpiration is diffusion
process
Flowers spread aroma
through diffusion to attract
insects and other animals for
pollination.
Importance of Diffusion
Defined as the diffusion of water or solvent across a
semipermeable membrane from a region of its higher
concentration to region of its lower concentration.
Plasma membrane functions as semipermeable
membrane.
Osmosis
Osmosis Osmosis - demonstration
Diffusion
It can take place in solid,
liquid and gases.
It does not involve any semi
permeable membrane.
It equalizes the
concentration of substances.
Different substances diffuse
independent of one another
Diffusion is not much
influenced by the presence
of other substances
How Diffusion differs from Osmosis ?
Osmosis
It takes place only in liquid
medium
It requires semi-permeable
membrane.
It does not equalize the
concentration of solvent on
the two sides of the
membrane
Only solvent undergoes
diffusion
It is influenced by the
concentration and type of
solute particles.
Osmotic solutions are those solutions which can cause
osmosis
They are three types• Hypotonic Solution, Isotonic Solution and Hypertonic
Solution
Hypotonic – which has an osmotic concentration lower
than another solution.
Isotonic – The solution has an osmotic concentration
similar to another solution.
Hypertonic – which has an osmotic concentration higher
than that of another solution.
Types of Osmotic Solutions
Osmosis is of two types • Endosmosis• Exosmosis
Endosmosis – Osmotic entry of water in to the cell or
system
Exosmosis – Osmotic withdrawal of water from a cell or
system
When we place the cell in higher concentration the
water comes out of the cell by a process called
exosmosis.
When we place the cell in lower concentration the
water enters in to the cell by a process called
endosmosis.
Types of Osmosis
En
dosm
os
is Exosm
osis
Rigid, semi elastic, semi transparent and
protective covering present outside the
plasma membrane in plant cells, fungi and
prokaryotes.
Made up of Cellulose in plants, Fungal
cellulose and Chitin in fungi
Extra deposition of lignin, suberin and
cutin may be present during secondary
thickening
A cementing layer called middle lamella is
present between the walls of two adjacent
cells
Cell wall possesses small pores through
which adjacent cells remain connected
called Plasmodesmata.
Cell Wall
Plasmodesmata.
Middle lamella.
It provides shape to the cells
It provides mechanical strength to plants
Protects against pathogens and mechanical injury
Growth of the cell wall determines the growth of the
cell
Cell wall prevents bursting of cell on endosmosis
Ability to withstand a lot of variation in nature.
What is the role of cell wall?
Does cell wall & Plasma membrane are similar in
function?
Cell Wall
occurs in plant cells
lies on the outside of
the cell
Rigid and thick
Cell wall is permeable
Formed of Cellulose,
Hemi cellulose and
Pectin.
Provide protection and
strength to the cell
Plasma Membrane
Occurs in plant & animal
cells
Lies on the outside of
animal cells and inside in
plants
Flexible and thin
Selectively Permeable
Lipids and Proteins with
small number of
carbohydrates
Hold cellular contents and
control of passage materials
Nucleus – The Cell Brain
Dense protoplasmic body that
contains hereditary information
controlling cell activities as well as for
transfer to next generation
It lies in median or central position
In mature plant cell it lies towards
periphery
In prokaryotes nuclear membrane is
absent
It is called Nucleoid.
Cells like RBC, Sieve Elements lack
Nucleus
Cells without Nucleus cannot survive
for longtime
One nucleus (uninucleate) is present
in most of cells but some cells may
have more than one (multi nucleate)
Nuclear Envelop is a double
membrane covering which separates
the nucleus from the cytoplasm. It
contains many Nuclear pores.
Nuclear pores allow exchange of
materials between the nucleus and
cytoplasm
Nucleoplasm – It is colorless, dense
sap found inside the nucleus in which
chromatin and nucleolus are
suspended.
Nucleolus – a round structure found in
side the nucleus, it is rich in RNA and
protein. It is site of ribosome
formation.
What is Nucleus made up of?
Nuclear EnvelopNucleoplasmNucleolus
THE NUCLEUS IS ENCLOSED BY A DOUBLE MEMBRANE
Nuclear Pore Complex-Diagram
Does cell wall & Plasma membrane are similar in
function?
Nucleus
It represent the whole
eukaryotic complex that
contains genetic
information
It is covered by a two
membrane envelop
It controls the structure
and working of cells
Nucleolus
It is a component of
nucleus
It is without a covering
membrane
It synthesizes ribosomal
subunits
Chromatin Material – An intervened mass of thread-like structure made of DNA and Proteins. During Cell Division, Chromatin becomes highly condensed, thick and rod like structures, Known as Chromosomes.
Thread like structures which are formed by condensation of
chromatin during cell division are called chromosomes they
referred as hereditary vehicles
Chromosomes are made of DNA & Proteins
A chromosome consists of two similar threads called
Chromatids
Two chromatids are attached at the center by a centromere
On either side of centromere chromatids are called arms
Chromosomes
Chromosome number is fixed for each species
In most organisms they occur in homologous pair
In each pair, one chromosome belongs to father parent
while other belongs to mother parent
Presence of two sets of chromosomes is called Diploid• 2n=46 ( in human)
Presence of singe set of chromosomes is called Haploid• n=23 (in human)
Chromosomes-Number
Nucleus contains all the genetic
information not only for the cell but
also the whole organism
It functions as control centre of the
cell as it controls cell metabolism
and cell activities
Ribosomes are formed by nucleolus
part of nucleus
Nucleus us brings about cell
differentiation by which a cell
attains a specific structure and
function.
Division of nucleus is essential for
cell division
Reshuffling of chromosomes and
changes in genes produce variations
Role of Nucleus in a Cell
Prokaryotes (singular ) are a group of organisms that
lack a cell nucleus or any other membrane-bound
organelles. They differ from the eukaryotes, which
have a cell nucleus. Prokaryotes are the single-celled
organisms, such as bacteria, and are roughly one
micrometre in diameter.
A eukaryote is an organism whose cells contain
complex structures inside the membranes. The
defining membrane-bound structure that sets
eukaryotic cells apart from prokaryotic cells is the
nucleus, or nuclear envelope, within which the genetic
material is carried
Prokaryotes & Eukaryotes
Bacteria Plant Cell
Prokaryotes do not have a nucleus that houses its genetic
material.
Prokaryote cell consists of a large DNA molecule compacted
in an area of cytoplasm called the nucleoid region.
The nucleoid region is protected and encased by the cell
wall, or cell membrane, the outer layering of the cell
(similar to human's skin). Finally,
Flagellum a rudder-like device, affords the prokaryote the
luxury of mobility.
Prokaryotes & Eukaryotes
Prokaryotes & Eukaryotes
Prokaryotes
Small in size, 1-10μm.
Organized nucleus is
absent.
A single DNA molecule is
present suspended in
cytoplasm, nucleolus is
absent
Membrane bound cell
organelles are absent
Typical vacuoles are absent
Mitosis is absent
Bacteria, Cyanobacteria
Eukaryotes
Larger in size, 5-100 μm
Organized nucleus is
present with nuclear
envelop, Nucleolus is
present, several DNA
molecules are present
Membrane bound cell
organelles are present
Typical vacuoles are
present
Mitosis is present
Plants, Animals, Fungi
Eukaryotic (Animal ) Cell
The contents of a cell except for the nucleus. It
includes cytosol, organelles, vesicles, and the
cytoskeleton
Cytoplasm has two parts, cytosol and cell organelles
Cytosol – is the fluid part of cytoplasm,
homogeneous and crystallocolloidal liquid that
contains substances water, ions, enzymes, vitamins,
amino acids, carbohydrates, lipids, proteins etc.,
Cell Organelles – Submicroscopic structure which
are specialized to perform specific cellular
functions.
Cell organelles may be bounded by a membrane as
in Eukaryotes but prokaryotes lack membrane bound
organelles
Virus lack cytoplasm as well as membrane
Cytoplasm
The endoplasmic reticulum (ER) is a network of interconnecting
membranes distributed throughout the cytoplasm.
The internal compartment, called the lumen, is a separate part
of the cell with a distinct protein and ion composition.
The ER’s folding generates a surface area much greater than
that of the plasma membrane.
At certain sites, the ER membrane is continuous with the outer
nuclear envelope membrane.
Depending upon the presence or absence of ribosomes on the
surface, there are two types of E.R.
Rough E.R. – Characterized by the presence of ribosomes on its
surface
Smooth E.R. – Devoid of ribosomes on its surface
Endoplasmic Reticulum
Endoplasmic Reticulum
Protein Synthesis – Rough E.R. is the site of Protein
synthesis
Lipid Synthesis – Smooth E.R. helps in lipid synthesis
Proteins and lipids synthesized on E.R. are used for
making cell membrane
Transport – helps in intercellular and intracellular
transport of substances
Support – it gives internal support to the cytoplasm
SER in liver cells takes part in detoxifying many
poisons and drugs
Functions of E.R.
SER
Ribosomes are absent
Synthesize lipids and steroids
Mainly formed of vesicles
and tubules
RER
Ribosomes are present
Synthesize proteins
Formed by cisternae
Golgi complex is an organelle of membrane bound sacs,
tubules and vesicles secrete complex biochemical
Golgi is a single complex in animal cells.
In plants they form separate units called dictyosomes.
Membrane bound sacs of Golgi are called cisternae.
Cisternae occurs in stacks, tubes and vesicles occur on
their periphery
Golgi Complex
Golgi Apparatus
Golgi apparatus is involved in repair and
synthesis of cell membranes
Lysosomes are formed by Golgi apparatus
All types of substances which are to be secreted
or excreted are packed in vesicles by Golgi
apparatus for passage to the outside
Takes part in storage, modification and
packaging of various biochemical produced by
different components of the cell
Components of cell wall are synthesized by
Golgi apparatus
Complex and special sugars are made by Golgi
apparatus
Functions of Golgi
Lysosomes
Lysosomes generally found in animal cells they lack in plant cell
Are small spherical vesicles covered by single membrane
contain digestive enzymes for intracellular digestion and waste
disposal
These enzyme are synthesized by R.E.R
In damaged cell, lysosomes burst to release enzymes for
digestion of cellular components
Functions
Destruction of foreign particles
Intracellular Digestion
Removal of cell debris
Time of metamorphosis
Organs are digested by Lysosomes
Lysosomes-suicide bags
Lysosomes-Kuffer cells
Mitochondria is rod-shaped cell organelles of aerobic
eukaryotes which take part in the Krebs cycle.
Commonly called “Power House of the Cell” because they
contain enzymes necessary for the total oxidation of food and
for release of high amount of energy in the form of ATP
It is bounded by two membrane- outer membrane is smooth and
porous while inner membrane is folded inwards to form Cristae
Cristae contains oxysomes they are partially embedded in inner
membrane
Mitochondria enclose a matrix having DNA, ribosomes and
enzymes.
DNA and ribosomes make the mitochondria semi-autonomous as
they are able to manufacture some of their own proteins and
enzymes.
Mitochondria (power House of a Cell)
Mitochondria
Lysosomes-suicide bags
Plastids are large cell organelles found only in plant
cells which are specialized to synthesize and store
organic substances.
Plastids are classified on the basis of pigment present
in them two types• Leucoplasts – colorless plastids (amyloplasts,
aleuroplast, elaioplasts• Chromoplasts – Coloured Plastids. Green & Non green
plastids
Plastids
Leucoplasts
colorless
Cylindrical to round in
shape
Found in un exposed cells
Take part in storage of
food
Can change to other types
Chromoplasts (non green)
Brown or reddish in colour
Irregular in shape
in exposed & un exposed
cell
Do not storage food
Provide coloration of organs
Bounded by two membranes. Inside of chloroplast is
clearly marked into a colorless matrix called Stroma
and Membranous system called Grana.
Each granum consists of stack of membrane bounded,
flattened sacs called thylakoids
Thylakoids pigments like chlorophyll, carotenoids and
phycobillins
Stroma contains enzymes for dark reaction, DNA, RNA
and ribosomes, latter make the chloroplasts
semiautonomous.
Chloroplast-kitchen of the cell
Chloroplast Chloroplast
Lysosomes-suicide bags
Chromoplasts provide color to fruits and flowers and
attract the animals to help in pollination and fruit
dispersal
Leucoplasts take part in storage of protein, starch and
oil
Chloroplasts trap solar energy to manufacture food
through photosynthesis
Oxygen is being consumed in combustion and
respiration. Carbon dioxide is being produced inn the
two process. Chloroplasts maintain the balance of the
two gases by absorbing carbon dioxide and oxygen in
photosynthesis.
Plastids-functions
Ribosomes are small rounded bodies found either in
free state in the cytoplasm or attached to the surface of
Endoplasmic Reticulum
They are composed of ribonucleic acid (RNA) and
proteins
They are not bounded by a membrane
They are present in both prokaryotes (70s=50s+30s)
eukaryotes (80s=60s+40s)
Absent in mammalian R.B.Cs.
Ribosomes are the site of protein synthesis in the cell
Ribosomes-Translation factory
It is a small naked organelle
present near the nucleus in the
cells of animals and some lower
plants.
It has sheath of special
cytoplasm called centrosphere.
It encloses two micro cylinders
called centrioles.
Two centrioles like right angles
to each other.
It has nine triplet fibrils
present obliquely on the
periphery.
They form astral spindle fibers
and produce basal bodies that
form cilia and flagella
Centrosome-central apparatus
Membrane bound non-cytoplasmic sacs that contain
non-living solid or liquid contents. They are of three
types- sap vacuoles, food vacuoles and contractile
vacuoles
Covering membrane of sap vacuole is called tonoplast
The fluid filled content of the vacuole is called cell sap
or tonoplasm
Recently digestive enzymes are reported in vacuole of
plant cell
Vacuoles-store house of the cell
Vacuoles-store house of the cell
Differences between Plant and Animal Cell
Cell wall is present
Plastids are present
Centrioles and
centrosomes are absent
Vacuoles large and less
Nucleus lie on one side
Cell is rigid
Golgi contains
dictyosomes
Larger in size
Starch is stored
absent
absent
Centrioles and
centrosomes are present
Vacuoles small and many
Nucleus lies in the
centre
Cell is flexible
In the form of vesicles
Smaller in size
Glycogen is stored
Plant and Animal Cell
R.V.Raghavendra Rao
PGTBiology
JNV Kiltampalem
Vizianagaram
Phone-9490811620
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