The word cell is derived from the Latin word “cellula” which means “a little room”
It was the British botanist Robert Hooke who, in 1664, while examining a slice of bottle cork under a microscope, found its structure resembling the box-like living quarters of the monks in a monastery, and coined the word “cells”
2. 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
3. D I S C OV E RY O F C E L L
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
4. TO KNOW THE
HISTORY OF CELL?
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”
Leeuw
enhoek
Robert
Hook
Rudolf
Virchow
M.J.Schleiden
Schwann
Robert
Brown
5. WHAT ARE LIVING
O RG A N I S M S M A D E U P O F ?
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.
6. G A D G E T S TO S T U DY C E L L S
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
7. Shape and Size of cells
Shape and size of cells vary but all of these are ultimately
determined by the specific function.
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.
10. UNICELLULAR VS.
M U LT I C E L L U L A R
Unicellular
Multicellular
Made of Single Cell
Made up of many number of cells
Single cell able to perform all the Cells
have
a
similar
life processes like obtaining food,
structure and similar basic
respiration, excretion, growth and
basic
activities
reproduction.
Cannot be divided in to cells, they
life
Different shapes and aggregated
to form different tissues
are also called acellular organisms Tissues form organs and organs
Amoeba, paramecium
give rise to organ system that
perform special function.
Plants, Animals and Fungi
11. Cell is basic unit of life
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
12. What is Cell made up of ?
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
13. Plasma Membrane-Cell Membrane
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.
15. Transport Across the 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.
16. Active & Passive Transport
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.
18. Passive 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.
Diffusion – Demonstration
19. Importance of Diffusion
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.
20. Osmosis
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 - demonstration
21. How Diffusion differs from
Osmosis ?
Diffusion
Osmosis
It can take place in solid,
It takes place only in liquid
medium
liquid and gases.
It does not involve any semi
It equalizes the concentration
of substances.
Different substances diffuse
independent of one another
is
not
much
influenced by the presence of
other substances
requires
semi-permeable
membrane.
permeable membrane.
Diffusion
It
It
does
not
equalize
the
concentration of solvent on the
two sides of the membrane
Only
solvent
undergoes
diffusion
It
is
influenced
concentration
solute particles.
and
by
the
type
of
22. Types of Osmotic Solutions
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.
23. Types of Osmosis
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.
Exosmosis
Endosmosis
24. Cell Wall
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
Plasmodesmata.
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
Plasmodesmata.
remain
connected
called
Middle lamella.
25. What is the role of cell wall?
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.
26. Does cell wall & Plasma membrane
are similar in function?
Cell Wall
Plasma Membrane
occurs in plant cells
Occurs in plant & animal cells
lies on the outside of the Lies on the outside of animal
cells and inside in plants
cell
Rigid and thick
Flexible and thin
Cell wall is permeable
Selectively Permeable
Formed of Cellulose, Hemi Lipids and Proteins with small
number of carbohydrates
cellulose and Pectin.
Provide
protection
strength to the cell
and
Hold cellular contents and
control of passage materials
27. 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)
28. What is Nucleus made up of ?
Nuclear Envelop
Nucleoplasm
Nucleolus
Nuclear Envelop is a double membrane
covering which separates the nucleus
from the cytoplasm. It contains many
Nuclear pores.
Nuclear
materials
pores
allow
between
the
exchange
of
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.
31. Does cell wall & Plasma membrane
are similar in function?
Nucleus
Nucleolus
It represent the whole eukaryotic
It is a component of nucleus
complex that contains genetic
information
It is covered by a two membrane
envelop
It controls the structure and
working of cells
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.
32. 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
33. Chromosomes-Number
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)
34. Role of Nucleus in a Cell
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
35. Prokaryotes & Eukaryotes
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
Plant Cell
Bacteria
36. Prokaryotes & Eukaryotes
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.
37. Prokaryotes & Eukaryotes
Prokaryotes
Eukaryotes
Small in size, 1-10μm.
Larger in size, 5-100 μm
Organized nucleus is absent.
Organized nucleus is present
A single DNA molecule is
present
suspended
in
cytoplasm, nucleolus is absent
Membrane
bound
cell
organelles are absent
with
nuclear
envelop,
Nucleolus is present, several
DNA molecules are present
Membrane
bound
cell
organelles are present
Typical vacuoles are absent
Typical vacuoles are present
Mitosis is absent
Mitosis is present
Bacteria, Cyanobacteria
Plants, Animals, Fungi
39. Cytoplasm
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
40. Endoplasmic Reticulum
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
42. Functions of E.R.
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
SER
RER
Ribosomes are absent
Ribosomes are present
Synthesize lipids and steroids
Mainly formed of vesicles and
tubules
Synthesize proteins
Formed by cisternae
43. Golgi Complex
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
45. Functions of Golgi
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
47. Lysosomes-suicide bags
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-Kuffer cells
48. Mitochondria (power House of a Cell)
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.
51. Plastids
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
Leucoplasts
Chromoplasts (non green)
colorless
Brown or reddish in colour
Cylindrical to round in shape
Irregular in shape
Found in un exposed cells
in exposed & un exposed cell
Take part in storage of food
Do not storage food
Can change to other types
Provide coloration of organs
52. Chloroplast-kitchen of the cell
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
Chloroplast
54. Plastids-functions
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
Oxygen is being consumed in combustion and respiration.
Carbon
photosynthesis
dioxide is being produced inn the two process. Chloroplasts maintain the
balance of the two gases by absorbing carbon dioxide and oxygen in
photosynthesis.
55. Ribosomes-Translation factory
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
56. Centrosome-central apparatus
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
57. Vacuoles-store house of the cell
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
59. Differences between Plant and
Animal Cell
Cell wall is present
absent
Plastids are present
absent
Centrioles and centrosomes Centrioles and centrosomes
are absent
are present
Vacuoles large and less
Vacuoles small and many
Nucleus lie on one side
Nucleus lies in the centre
Cell is rigid
Cell is flexible
Golgi contains dictyosomes
In the form of vesicles
Larger in size
Smaller in size
Starch is stored
Glycogen is stored