CELL – BASIC UNIT OF LIFE
ch 5

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
Leeuw
enhoek
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

Active Transport

Active Transport

Active Transport

Active 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
Endosmosis
Exosmosis

 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 Envelop
Nucleoplasm
Nucleolus

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

Adhweat Gupta
Class – 9th ‘D’
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