3. INSIDE
● CELL AS A BASIC UNIT OF LIFE
● PROKARYOTIC & EUKARYOTIC
CELLS
● STRUCTURE OF CELL
● PLASMA MEMBRANE
● NUCLEUS
● CYTOPLASM
● DIFFERENCES BETWEEN PLANTS
& ANIMAL CELLS
4. CELL AS A BASIC UNIT OF
LIFE
●Our earth is inhabited by different
kinds of living organisms, which look
very different from each other. These
living organisms are bacteria, protista
(Amoeba, Chlamydomonas), fungi,
plants and animals. The bodies of
living organisms are made up of
microscopic units called cells. The
cell has same central position in
5. ●On the basis of number of cells
an individual is made up of
organisms, are divided into two
categories : -
1.UNICELLULAR ORGANISMS :-
Organisms made up of
one cell only
2.MULTI-CELLULAR
ORGANISMS : -
6. UNICELLULAR
ORGANISMS
MULTICELLULAR
ORGANISMS
●Organisms made up of
a single cell.
●Organisms made up of more than one
cell.
●Single cell carries out all
the vital functions of
life.
●Different cells carry out
different functions of life.
●Cell is sufficiently large.
For example : -
Bacteria, amoeba,
Euglena etc.
●Cells are of various sizes, some small &
some are larger in size.
For example : -
Human beings, plants etc.
7. PROKARYOTIC &
EUKARYOTIC CELLS
● According to above criteria,
all living organisms present
on earth can be classified
into following two types :
8. NON-CELLULAR
ORGANISMS
●Non cellular organisms which
do not contain any cell in their
body organisation e.g., viruses.
Viruses lack any membrane
and hence do not show
characteristics of life until they
enter a living body (i.e.
prokaryotic cell or eukaryotic
9. CELLULAR
ORGANISMS
●Cellular organisms which
contains either one or many
cells in their bodies, e.g.,
bacteria, plants and animals.
●Cellular organisms are again
divided into following two
main types :
1. Prokaryotes
10. PROKARYOTIC CELL EUKARYOTIC CELL
●Size of the cell is generally
small (1-10µm)
●Size of cell is generally large
(5-100µm).
●Nucleus is absent (Nuclear
region or nucleoid is not
surrounded by a nuclear
membrane).
●Nucleus is present (Nuclear
material is surrounded by a
nuclear membrance).
●It contains single
chromosome.
●It contains more than one
chromosome.
●Nucleolus is absent. ●Nucleus is present.
●Membrane bound cell
organelles are absent.
●Membrane bound cell
organelles are present.
●Cell division takes place by
fission or budding (no
mitosis).
●Cell division occurs by mitotic
or meiotic cell division.
11. STRUCTURE OF
CELL
●The size, shape, number
and volume of the cell
vary greatly among
unicellular and
multicellular organisms.
12. CELL SHAPE
○The basic shape of eukaryotic cell is
spherical but the shape of cell is
ultimately determined by the specified
function of the cell. Thus, the shape of
the cell may be variable (i.e. frequently
changing its shape) or fixed. Variable
or irregular shape occurs in amoeba
and white blood cells or leucocytes. In
fact, leucocytes are spherical in the
circulating blood, but in other
conditions they may produce
pseudopodia and become irregular in
shape.
13. CELL SIZE
●The size of different cells ranges
between broad limits. Some plant and
animal cells are visible to the naked eye.
Most cells, however, are visible only with
a microscope, since they are only a few
micrometres in diameter. A micrometre
(µm) is one thousand of a millimetre. The
size of cells varies from the very small
cells of bacteria (0.2 to 5.0 µm) to the
very large eggs of the ostrich (18 cm)
14. CELL VOLUME
● The volume of a cell is fairly
constant for a particular cell type &
is independent of the size of the
organism. For example, kideny or
liver cells are about the same size in
the bull, horse and mouse. The
difference in the total mass of the
organ or organism depends on the
number, not on the volume of the
cells. Thus, the cells of an elephant
are not necessarily large than those
15. CELL NUMBER
●The number of cells in most
multicellular organisms is
indefinite, but the number of
cells may be fixed in some
multicellular organisms such as
rotifers and nematodes. The
number of cells in multi-cellular
organisms usually is correlated
with size of the organism.
Thus, small sized organism has
16. DETAILED STRUCTURE OF
CELL
●Though their shape, size and
activities vary, all cells have
three major functional regions
:
●The plasma membrane or cell
membrane.
●The nucleus, and
19. NATURE &
OCCURRENCE
■Most cellular organelles such as
mitochondria, chloroplasts,
lysosomes, peroxisomes, Golgi
apparatus, nucleus and
endoplasmic reticulum are all
enclosed by the unit membrane.
The cell surface membrane or
plasma membrane is the outer
20. STRUCTURE
■Plasma membrane is a living,
thin, delicate, elastic, selectively
permeable membrane. It is about
7 µm (70Å) thick. Under the light
microscope this merely appears
as a single line. However, the
development of electron
microscope has made it possible
21. FUNCTIONS
●Plasma membrane permits the entry
and exit of some materials in the
cells. It also prevents movement of
some other materials. Therefore, the
plasma membrane is called a
selectively permeable membrane.
●Entry or exit of materials through the
plasma membrane take place by two
processes.
22. DIFFUSION OSMOSIS
●Diffusion can occur in any
medium.
●It occurs only in liquid
medium.
●The diffusing molecules
may be solids, liquids or
gases.
●It involves movement of
solvent molecules only.
●Semipermeable membrane
is not required.
●Semipermeable membrane
is required.
●It is dependent upon the
free energy of the
molecules of diffusing
substance only; presence of
other substances in the
system is of no importance.
●Though it is the diffusion
of solvent molecules only,
yet influenced by the
presence of other
substances (solutes) in the
system.
●An equilibrium in the free
energy of diffusion
●Equilibrium in the free
energy of solvent molecules
25. NATURE &
OCCURRENCE
●The nucleus is a major, centrally
located spherical cellular
component. It is bounded by
two nuclear membranes, both
forming a nuclear envelope.
Nuclear envelope encloses a
space between two nuclear
membranes and is connected to
26. FUNCTIONS
●The nucleus controls all
metabolic activities of the cell. If
the nucleus is removed from a
cell, the protoplasm ultimately
dries up and dies.
●It regulates the cell cycle.
●It is concerned with the
transmission of hereditary traits
28. NATURE &
OCCURRENCE
●The part of the cell which occurs
between the plasma membrane and
nuclear envelope is called the cytoplasm.
The inner granular mass of the
cytoplasm is often called endoplasm,
while the outer, clearer (glassy) layer is
called cell cortex or ectoplasm.
●Cytoplasm consists of an aqueous
ground substance, the cytosol,
containing a variety of cell organelles
and other inclusions such as insoluble
29. CYTOSO
L
●It is the soluble part of cytoplasm. It
forms the ground substance or
“background material” of the cytoplasm
and is located between the cell
organelles. Cytosol is about 90 per cent
water and forms a solution which
contains all biochemicals of life.
●Cytosol (cytoplasm) acts as a store of
vital chemicals such as amino acids,
glucose, vitamins, ions, etc. It is the site
30. CELL ORGANELLES
●A cell has to perform different functions with
the help of its various membrane bound
organelles :
●It has to synthesize substances, eg.
Protein synthesis by ribosomes,
photosynthesis of food by chloroplasts.
●It has to secrete cell products, e.g.
enzymes, ormones, mucus, etc.
●It has to digest those substances which
are taken up by the cell during
endocytosis.
32. ENDOPLASMIC RETICULUM
(ER)
● Inside the cell there exists a
membranous network enclosing a
fluid-filled lumen which almost
fills up the intracellular cavity. It
is called endoplasmic reticulum
(ER). On the one end ER is
connected to the outer membrane
of the nucleus and on the other
end to the plasma mebrane.
● Endoplasmic Reticulum is of
two types :
33. RIBOSOMES
■Ribosomes are dense, spherical
and grannual particles which occur
freely in the matrix (cytosol) of
remain attached to the endoplasmic
reticulum (RER). Chemically, the
major constituents of ribosomes are
the ribonucleic acid (RNA) and
proteins. Lipids are virtually absent
in ribosomes.
35. GOLGI APPARATUS
●The Golgi apparatus, first
described by Camillo Golgi,
consists of a system of
membrane-bound vesicles
arranged aprpoximately parallel
to each other in stacks called
cisterns.
●It is used for storage,
37. LYSOSOMES
●Lysosomes are a kind of waste
disposal system of the cell. Each
lysosome is a small vesicle
srrounded by a single membrane
and contains powerful enzymes.
These enzymes are capable of
digesting or breaking down all
organic material.
●During breakdown of cell structure,
38. MITOCHONDRIA
●Mitochondira are known as the
power houses of the cell. The
energy required for various chemical
activities needed for life is released
by mitochondria in the form of ATP
(Adenosine triphoshate) molecules.
ATP is known as the energy
currency of the cell.
●Mitochondira are strange organelles
in the sense that they have their own
40. PLASTIDS
●Plastids occur in most plant cells and
are absent in animal cells. Plastids are
of following three types :
● Chromoplasts : Coloured plastids
● Chloroplasts : Green coloured plastids
● Leucoplasts : The colourless plastids
●Chloropasts trap solar energy & utilise
it to manufacture food for the plant.
●Chromoplasts impart various colours
to flowers to attract insects for
pollination.
●Leucoplasts store food in the form of
41. VACUOL
ES
■Vacuoles are storage sacs for solid
or liquid contents. Vacuoles are
small sized in animal cells while
plant cells have very large vacuoles.
The central vacuole of some plant
cells may occupy 50-90%of the cell
volume.
■Vacuoles help to maintain the
osmotic pressure in a cell
(osmoregulation). They store toxic
45. ANIMAL CELL PLANT CELL
●Animal cells are generally
small in size.
●Plant cells are large than
animal cells.
●Cell wall is absent. ●The plasma membrane of
plant cells is surrounded by a
rigid cell wall of cellulose.
●Except the protozoan
Euglena, no animal cell
possesses plastids.
●Plastids are present.
●Vacuoles in animal cells are
many, small and temporary.
●Most mature plant cells have
a permanent & large central
sap vacuole.
●Animal cells have a single
highly complex & prominent
Golgi apparatus.
●Plant cells have many
simpler units of Golgi
apparatus, called
dictyosomes.
●Animal cells have ●Plant cells lack centrosome &
