Study of the cell at school level

1. 1
Cell:
The
unit
of
life
Guruda2a
K
Wagh

2. 2
Cell:
The
unit
of
life

3. 3
Cell:
The
unit
of
life
Cell
• The
common
basic,
structural
and
func7onal
unit
of
living
beings
-­‐
Robert
Hooke
1665
Cell
theory
• All
plants
are
composed
of
cells;
cell
is
the
basic
unit
of
life
-­‐
MJ
Schleiden
and
T
Schwann,
1838-­‐39
• All
cells
arise
from
exis7ng
cells
-­‐
R
Virchow,
1885
modified
the
cell
theory
Modern
cell
theory
postulates
• All
organisms
are
composed
of
cells
• Cell
is
the
structural
and
func7onal
unit
of
life.
All
vital
func7ons
of
an
organism
occur
within
cells
• All
cells
arise
from
pre-­‐exis7ng
cells.
No
cell
originates
on
its
own
• Every
organism
starts
its
life
as
a
single
cell

4. 4

5. 5
Unit
to
measure
size
of
a
cell
• micrometer
(µm)
1
micrometer
=
1/1000
mm
=
10-­‐3
mm
=
0.001
mm
(1
metre
=
1000
mm
=
1,000,000
microns;
1
mm
=
1000
microns;
1
micron
=
0.001
mm)
(milli
m=
0.001/
10-­‐3;
micron
µ=0.000,001/
10-­‐6;
nano
n=0.000,000,001/
10-­‐9)
• Egg
and
an
amoeba
-­‐
are
single
cells
Small
size
of
cell
ensures
• Greater
surface
area
• Greater
diffusion
of
nutrients
into
the
cell
• Greater
extent
of
exchange
of
materials
in
and
out
of
the
cells
• Easy
repair
of
the
damaged
cell
Smallest
cell
• Mycoplasma
gallisep.um
(0.1
µm).
Bacterium,
causa7ve
agent
of
chronic
respiratory
disease
(CRD)
in
chickens
and
infec7ous
sinusi7s
in
turkeys,
chickens,
pigeons
Largest
cell
• Egg
of
an
ostrich
-­‐
18
cm
diameter

6. 6
Shapes
of
cells

7. 7
 Shapes
of
cells
a) Branched
b) Circular
c) Circular
biconcave
d) Columnar
e) Irregular
f) Oval
g) Rectangular
h) Rod
shaped
i) Spiral
j) Spindle
shaped
 Shapes
of
cells
–
funcAons
they
perform
• Human
RBCs
circular
biconcave
for
easy
passage
through
human
capillaries
• WBCs
change
their
shape
to
engulf
microorganisms
• Nerve
cells
are
long
to
conduct
impulses
from
one
point
to
another

8. 8
 Parts
of
a
cell
1. Cell
wall
(in
plant
cell)
2.
Plasma
membrane
3.
Cytoplasm
4.
Cell
organelles

9. 9

10. 10
 Plasma
membrane
Cell
is
bound
by
a
thin
covering
which
separates
the
contents
of
the
cell
from
its
external
environment
Living,
extremely
delicate
elas7c
membrane
of
about
70A°
thickness
(
1
A°
=
1Oµm
=
10-­‐7
mm)
made
up
of
a
lipid
bilayer
(two
molecule
thick
layer)
having
integrated
protein
molecules
-­‐
described
as
a
'number
of
protein
icebergs
floa7ng
in
the
sea
of
lipids'
Organiza7on
of
the
plasma
membrane
is
not
fixed
but
flexible
 SelecAvely
permeable
membrane
• Useful
molecules
enter
the
cell
(eg.
water,
salt,
oxygen)
• Useful
products
remain
in
the
cell
(eg.
enzymes,
proteins)
• Waste
and
other
secre7ons
leave
the
cell
(eg.
carbon
dioxide)
 Homeostasis
=
a
constant
internal
environment
is
maintained
inspite
of
changes
outside

11. 11
 Osmosis
A
process
by
which
molecules
of
a
solvent
tend
to
pass
through
a
semipermeable
membrane
from
a
less
concentrated
soluAon
into
a
more
concentrated
one
Passage
of
water
from
a
region
of
high
water
concentra7on
through
a
selec7vely
permeable
membrane
(Plasma
membrane)
to
a
region
of
low
water
concentra7on
Pure
mechanical
process,
cell
gains
water
without
spending
energy
When
a
cell
is
placed
into
a
solu7on
of
sugar
or
salt
-­‐
three
possible
situaAons
 Isotonic
solu7on
-­‐
Medium
surrounding
the
cell
has
same
water
concentra7on
as
that
of
the
cell
 Hypotonic
solu7on
-­‐
Medium
surrounding
the
cell
has
higher
water
concentra7on
than
that
of
the
cell
i.e.
outside
solu7on
is
very
dilute
 Hypertonic
solu7on
-­‐
Medium
surrounding
the
cell
has
lower
water
concentra7on
than
that
of
the
cell
i.e.
outside
solu7on
is
more
concentrated
 Plasmolysis
-­‐
shrinkage
of
cytoplasm
in
a
cell
when
placed
in
hypertonic
solu7on

12. 12
 Diffusion
Diffusion
is
the
movement
of
molecules
from
a
high
concentraAon
to
a
low
concentraAon
e.g.
taking
in
oxygen
from
the
air
in
the
body
and
giving
out
carbon
dioxide.
Ac7ve
cellular
process,
needs
energy.
 Endocytosis
-­‐
engulfing
the
food
and
other
material
from
external
environment
 Exocytosis
-­‐
throwing
out
the
waste
and
secretory
material
Diffusion
Osmosis
It
occurs
in
any
medium
It
requires
liquid
medium
The
diffusing
molecules
can
be
solid,
liquid
It
involves
movement
of
only
solvent
or
gases
molecules
Semipermeable
membrane
is
not
required
Semipermeable
membrane
is
required

13.
Osmosis
in
plant
cells
13

14.
Osmosis
–
plant
and
animal
cells
14

15. 15
Cell
wall
• Plant
cells,
rigid
outer
covering,
just
outside
the
plasma
membrane
• Non-­‐living
and
freely
permeable
(allows
all
sorts
of
substances
to
enter
and
leave
the
cell
freely)
• Made
up
of
cellulose
(a
type
of
carbohydrate)
• Gives
protec7on
to
the
cell,
also
determines
its
shape
• In
a
hypotonic
solu7on
the
cell
absorbs
water
and
swells
due
to
osmosis
and
becomes
turgid.
But
the
presence
of
cell
wall
in
plant
cells,
bacteria
and
fungi
help
the
cells
to
counter
balance
the
pressure
exerted
by
the
vacuole
which
is
filled
with
water

16. 16
Cytoplasm
-­‐
fluid
which
lies
in
between
the
plasma
membrane
and
nucleus
• Living
cytoplasm
-­‐
constantly
moving,
jelly-­‐like
substance
• Many
cell
organelles
lie
in
the
cytoplasm
• Cellular
chemical
reac7ons
take
place
in
the
cytoplasm
• The
part
of
cytoplasm
other
than
organelles
is
called
cytosol.
It
stores
vital
substances
like
amino
acids,
glucose,
vitamins
etc.
• In
animal
cells
cytoplasm
is
more
granular
and
dense
while
in
plant
cells
it
is
thin
and
mostly
pushed
to
the
periphery
due
to
a
larger
central
vacuole
Organelle
-­‐
specialized
subunit
within
a
cell
that
has
a
specific
func7on,
and
is
usually
enclosed
within
its
own
lipoprotein
membrane
• Except
nucleus
and
chloroplast
all
the
organelles
are
seen
only
with
the
help
of
electron
microscope
• Various
cell
organelles
are
embedded
in
the
cytosol.
They
are
'Organs
of
a
cell'
• Each
organelle
is
living
and
performs
a
specific
func7on
• It
has
a
definite
shape,
structure
and
is
bounded
by
a
membrane

17.
Plant
cell
17

18. Animal
cell
18

19. Nucleus
19

20. 20
 Nucleus
-­‐
large
spherical
body,
at
the
centre
of
a
cell
Most
important
part
of
the
cell,
controls
all
the
cellular
ac7vi7es,
plays
an
important
role
in
cell
division,
decides
what
func7on
a
cell
will
carry
out
aier
matura7on.
When
observed
with
the
help
of
an
electron
microscope
we
can
see
nucleus
covered
by
a
double
layered
nuclear
membrane.
The
nuclear
membrane
has
pores
which
allow
the
transfer
of
products
from
inside
the
nucleus
[nucleoplasm]
to
the
outside
[cytoplasm].
The
nucleoplasm
contains
one
or
more
round
shaped
nucleoli
[singular-­‐nucleolus]
and
a
network
of
fibres
called
chroma7n
fibres
 Nucleolus
-­‐
one
or
more
in
number,
not
bound
by
a
membrane
Chroma7n
fibres
-­‐
thin
thread
like
structures
composed
of
DNA
[Deoxyribo
nucleic
acid]
and
protein.
These
fibres
condense
to
form
short
thick
chromosomes
during
cell
division
and
become
visible.
DNA
molecules
transfer
the
hereditary
informa7on
from
one
genera7on
to
the
next.
Func7onal
segments
of
DNA
are
called
genes.
Generally
one
gene
controls
one
or
more
cell
func7on
but
some7mes
a
single
func7on
is
controlled
by
a
set
of
genes.

21. 21
 Nucleus
FuncAons
• It
controls
all
metabolic
ac7vi7es
of
the
cell.
If
it
is
removed,
the
cell
ul7mately
dies
• Nucleus
controls
cell
division
• It
is
involved
in
transmission
of
hereditary
characters
from
parents
to
offsprings
In
the
RBCs
of
humans
and
other
mammals
nuclei
disintegrate
due
to
which
there
is
more
space
to
carry
haemoglobin
and
to
absorb
more
oxygen
In
plant
cells
like
sieve
tubes,
the
same
thing
happens
and
they
become
hollow
for
easier
flow
of
materials.

22.
Endoplasmic
reAculum
22

23. 23
Endoplasmic
ReAculum
(ER)
• Intracellular
transport
system
of
a
cell
• Large
network
of
membrane
bound,
fluid
filled
inter
connec7ng
tubules
and
sheets
• ER
spreads
from
the
nuclear
membrane
to
the
plasma
membrane
Two
types
Rough
endoplasmic
reAculum
(RER)
• Looks
rough
under
an
electron
microscope
as
it
has
par7cles
called
ribosomes
amached
to
it.
• Ribosomes
are
present
in
all
ac7ve
cells.
They
are
the
sites
where
proteins
are
synthesized.
• RER
helps
to
transport
the
proteins
synthesized
by
ribosome
to
that
part
of
the
cell
where
they
are
needed.
Smooth
endoplasmic
reAculum
(SER)
• Is
without
ribosome
and
is
meant
for
manufacture
of
fat
molecules
or
lipids

24. 24
Endoplasmic
reAculum
FuncAons
• Along
with
intracellular
transport
it
also
acts
as
a
suppor7ve
framework
for
a
cell
• It
synthesizes
proteins
and
lipids
(fats)
and
transports
them.
Some
lipids
synthesized
by
it
are
used
in
building
plasma
membrane
while
some
other
lipids
and
proteins
are
used
as
hormones
and
enzymes
• It
transports
proteins
synthesized
by
ribosomes
• SER
of
certain
cells
of
liver
play
a
crucial
role
in
detoxifying
many
poisons
and
drugs
which
enter
our
body
through
food,
air
or
water.
It
makes
the
toxins
water
soluble
so
that
they
may
be
excreted
through
urine

25.
Rough
endoplasmic
reAculum
at
work
25

26. Golgi
apparatus
26

27. 27
Golgi
apparatus
(Golgi
complex)
• Described
by
a
German
scien7st
Camillo
Golgi
• It
comprises
of
five
to
eight
(some7mes
more)
sacs
which
resemble
deflated
balloons
placed
approximately
parallel
to
each
other
• These
sacs
are
called
cisternae
and
are
filled
with
different
enzymes.
It
is
considered
as
the
packing
and
forwarding
department
of
the
chemical
factory
of
a
cell
• The
proteins
built
in
the
SER
and
RER
come
out
enclosed
in
vesicles
and
move
through
the
cytoplasm.
When
they
reach
the
golgi
apparatus
they
fuse
with
the
cis
face
(forma7on
face)
of
the
go1gi
membranes
and
empty
their
contents
in
the
cisternae.
As
they
pass
from
fold
to
fold,
they
are
biochemically
modified
by
the
enzymes
present
in
the
cisternae
and
are
packed
again
in
the
vesicles.
These
vesicles
exit
from
the
trans
face
(matura7on
face).

28. 28
Golgi
complex
FuncAons
• Golgi
complex
is
the
secretory
organ
of
the
cell
• It
modifies,
sorts
and
packs
materials
synthesized
in
the
cell
(enzymes,
mucous
secre7ons,
proteins,
lipids,
pigments,
etc.)
and
dispatches
them
to
various
targets
inside
the
cell
(eg.
plasma
membrane,
lysosomes)
or
outside
the
cell
• It
produces
vacuoles
and
secretory
vesicles
• It
plays
the
role
in
forma7on
of
the
cell
wall,
plasma
membrane
and
lysosomes

29.
Lysosome
structure
29

30. 30
Lysosome
• Lysosomes
digest
the
waste
• Lysosomes
are
simple
one
membrane
bound
sacs,
filled
with
diges7ve
enzymes.
These
powerful
enzymes
are
made
by
RER
and
are
capable
of
diges7ng
and
breaking
down
all
organic
mamer.
It
is
the
cell's
waste
disposal
system.
Very
few
lysosomes
are
present
in
plant
cells.
FuncAons
•
As
it
is
the
diges7ve
system
of
the
cell,
it
protects
the
cell
by
destroying
any
foreign
material
like
bacteria
and
viruses
that
invade
the
cell
•
They
remove
worn
out
cellular
organelles
and
remove
all
the
organic
debris.
This
process
is
called
autolysis.
So
they
are
called
as
'Demoli7on
Squads‘
•
When
a
cell
gets
old
or
is
damaged,
lysosomes
burst
and
the
enzymes
digest
their
own
cells.
Therefore
lysosomes
are
also
called
as
'Suicide
Bags‘
•
During
starva7on,
lysosomes
digest
stored
proteins,
fats
to
supply
necessary
energy
•
When
tadpole
transforms
into
frog,
the
tail
is
digested
by
lysosomes

31.
Mitochondrion
31

32. 32
Mitochondrion
(plural
mitochondria)
• Power
house
of
the
cell
-­‐
produces
the
energy
for
the
cell
• A
mitochondrion
has
a
double
membrane
structure.
The
outer
membrane
is
porous
while
the
inner
membrane
is
deeply
folded.
These
folds
are
called
cristae.
They
create
a
larger
surface
area
for
efficient
func7oning
• The
interior
cavity
is
filled
with
proteinaceous
gel
like
matrix
which
contains
ribosomes,
phosphate
granules
and
DNA.
Therefore
they
are
capable
of
making
some
of
their
own
proteins
• Mitochondria
oxidise
carbohydrates
and
fats,
present
in
the
cells,
with
the
help
of
enzymes.
During
this
process,
large
amount
of
energy
is
released,
which
is
used
by
the
mitochondria
to
produce
energy-­‐rich
compound
ATP
(Adenosine
tri
phosphate)
• There
are
numerous
mitochondria
in
animal
cells
whereas
plant
cells
have
fewer
mitochondria

33. 33
Mitochondrion
FuncAons
• Mitochondria
produce
the
energy
rich
compound
ATP
which
is
the
energy
currency
of
the
cell
• The
body
uses
the
energy
stored
in
ATP
to
synthesize
chemical
compounds
(proteins,
carbohydrates,
lipids,
etc.)
and
to
do
mechanical
work
(movement
of
muscles,
conduc7on
of
nerve
impulses,
produc7on
of
heat,
etc.)
• RBCs
do
not
have
mitochondria
hence
these
cells
do
not
use
any
of
the
oxygen
they
transport.
Think-­‐What
would
happen
if
mitochondria
are
present
in
RBCs?

34. 34
PlasAds

35. 35
PlasAds
• Organelles
that
give
colour
to
leaves,
flowers,
fruits
• Double
membrane
structures
present
only
in
plant
cells
Two
types
 Chromoplasts
(coloured-­‐plas7ds)
 Chlorophyll
-­‐
green
pigment
Chloroplasts
(Chloroplast
can
get
converted
to
other
type
of
chromoplast,
eg.
raw
green
tomatoes
get
converted
to
red)
 Carotene
-­‐
gives
orange
colour
 Xanthophyll
-­‐
gives
yellow
colour
 Leucoplasts
(white
or
colourless
plas7ds)
FuncAons
• Chloroplasts
help
to
harness
solar
energy
and
convert
it
into
chemical
energy
in
the
form
of
food
• Chromoplasts
give
colour
to
flowers
and
fruits
• Leucoplasts
are
involved
in
the
synthesis
and
storage
of
various
kinds
of
food
like
starch,
oils
and
proteins

36.
Chloroplast
36

37. 37
 Chloroplasts
• Important
for
photosynthesis
in
plants.
• These
are
'energy
factories'
of
plant
cells.
Chlorophyll
traps
solar
energy
and
convert
it
to
chemical
energy'.
This
energy
is
stored
into
chemical
bonds
produced
during
synthesis
of
food,
i.e.
starch.
 Each
chloroplast
shows
two
dis7nct
regions.
1. Stroma
It
is
the
colourless
proteinaceous
matrix
having
various
photosynthe7c
enzymes,
DNA,
ribosomes,
and
starch
granules
2.
Granum
(plural
Grana)
It
is
stack
of
thylakoids
which
are
the
discs
containing
chlorophyll
and
other
photosynthe7c
pigments.
The
tubes
joining
grana
are
called
inter-­‐granal
lamellae.
Due
to
presence
of
DNA
and
ribosomes,
plas7ds
can
self-­‐replicate
like
mitochondria

38. Vacuole
38

39. 39
Vacuoles
• Vacuoles
are
storage
sacs
for
solid
or
liquid
contents
• They
do
not
have
any
basic
shape
or
size
• The
structure
of
the
vacuole
changes
according
to
the
need
of
the
cell
• There
are
few
small
sized
and
temporary
vacuoles
in
animal
cells,
while
plant,
cells
have
one
or
more
large
vacuoles
• Vacuole
is
bound
by
a
single
membrane,
i.e.
it
is
one
layered
FuncAons
• Vacuoles
help
to
maintain
osmo7c
pressure
of
the
cell
• They
store
metabolic
by-­‐products
and
end
products
e.g.
Glycogen,
proteins
and
water
• They
store
waste
products
and
food
in
animal
cell.
e.g.
in
amoeba
it
stores
food
so
it
is
called
as
food
vacuole
• In
plant
cells,
vacuoles
are
full
of
cell
sap
and
provide
turgidity
and
rigidity
to
them

40. 40
ProkaryoAc
and
EukaryoAc
cells

41.
ProkaryoAc
and
EukaryoAc
cells
41

42. 42
 PROKARYOTIC
AND
EUKARYOTIC
CELLS
EUKARYOTIC
CELLS
In
Greek;
Eue
=
true,
karyone
=
nut
or
kernel
referring
to
nucleus
Cells
having
membrane-­‐bound
organelles
are
called
Eukaryo7c
cells
 CharacterisAcs
They
have
a
well
defined
nucleus,
i.e.
with
nuclear
membrane,
nucleolus
and
nucleoplasm
•
Size
of
the
eukaryo7c
cells
ranges
from
5-­‐100
µm
i.e
they
are
compara7vely
large
in
size
•
They
have
more
than
one
chromosome
•
They
are
present
in
higher
advanced
unicellular
and
mul7cellular
plants
and
animals

43. 43
 ProkaryoAc
cell
In
Greek;
Pro
=
before,
karyone
=
nut,
kernel
Can
there
be
cells
without
membrane
bound
organelles?
Cells
present
in
prokaryo7c
organisms,
do
not
have
membrane
bound
organelles.
Such
cells
called
as
the
prokaryo7c
cells
 CharacterisAcs
•
Prokaryo7c
cells
have
three
basic
structures,
plasma
membrane,
cytoplasm,
and
nuclear
material
•
Their
nucleus
lacks
nuclear
membrane.
Therefore
their
gene7c
material
(DNA)
lies
in
direct
contact
with
the
cytoplasm.
They
contain
a
single
chromosome.
Such
undefined
region
of
the
cytoplasm
containing
DNA
is
called
nucleoid.
•
Membrane
bound
organelles
such
as
mitochondria
are
absent
in
prokaryo7c
cells.
In
photosynthe7c
bacteria
or
blue-­‐green
algae,
chlorophyll
is
present
in
vesicles
(bag-­‐like
structures)
and
not
in
plas7ds.
•
Prokaryo7c
cells
are
smaller
in
size
ranging
from
1-­‐10
µm.

44. 44
The
following
YouTube
clip
will
help
immensely
in
understanding
the
chapter.
hmps://www.youtube.com/
watch?v=URUJD5NEXC8

45. 45
Thank
you
• Images
are
amributed
to
Google
images
• The
content
is
amributed
to
Standard
IX
text
book
of
the
MSBSHSE,
Government
of
Maharashtra,
India
• Video
clips
are
amributed
to
YouTube
SuggesAons
and
appreciaAons
welcome
gkwagh@gmail.com