IX-5-The fundamental unit of life science .ppt

Fundamental Unit of life

1. CHAPTER - 5
THE FUNDAMENTAL UNIT OF LIFE
CLASS :- IX
SUBJECT :- SCIENCE

2. INTRODUCTION
Any structure of a plant or animal is when
seen under microscope it is found that it
is made up of many, small units called
cells. Cells are very small and cannot be
seen by naked eyes.
Cell: Cell is a Latin word for ‘a little
room’. Cell is the smallest, structural
and functional unit of life. There are
two types of cell: prokaryotic cell
(bacterial cell) and eukaryotic cell (plant
cell and animal cell).

3. Cork cell

4. DISCOVERY
❑Cell: Robert Hooke (1665).
❑Free living cells in pond water (Bacteria):
Anton Van Leeuwenhoek (1671).
❑Nucleus: Robert Brown (1831).
❑Protoplasm: Purkinje (1839).
❑Cell theory: Schleiden (1838) and
Schwann (1839) in plants and animals
respectively.
❑All cell arises from pre existing cell:
Virchow (1855)

5. WHAT ARE LIVING ORGANISM
MADE UP OF
All living organisms are made up of cells. Cells
can be easily seen in an onion peel. Shape and
size of the cell varies according to the
function. It may be cuboidal, polygonal,
elliptical, small or very large.
Smallest cell: PPLO ( Pleuro Pneumonia Like
organism ). It is called mycoplasma
Largest cell: Ostrich egg.
Smallest cell in our body: Red blood cell.
Largest cell in our body: Nerve cell (neuron).

6. SMALLEST CELL
LARGEST CELL
SMALLEST CELL IN OUR BODY
LARGEST CELL IN OUR BODY

7. UNICELLULAR AND
MULTICELLULAR
❑There are some organisms which are made up of only
single cell as in Amoeba, Euglena, Bacteria etc.These
organisms are called unicellular organism.
❑When many cells are grouped together in a single
organism then they are called multicellular organism.
E.g. Fungi, Plants, animals. Different cells perform
different functions in these organisms. Every
multicellular organism has come from a single cell. All
the cells thus come from pre-existing cell ( Omnis
Cellulae cellula ). Cells which are produced from single
cell may differentiate to have different structures and
function. In multicellular organism there is division of
labour. This means that different part of an organism
perform different function.

8. UNICELLULAR ORGANISMS

9. MULTICELLULAR ORGANISM

10. ANIMALS

11. STRUCTURAL ORGANIZATION OF A
CELL
All the cells are made up of :
❖Plasma membrane
❖Nucleus
❖Cytoplasm
Plant cells have cell wall in addition to the above
components.
❖Plasma membrane/cell membrane:
✔Discover by C.Nageli and C. Cramer in 1855.
✔It is the outermost covering of cell except plant cell
that separates the contents of the cell from its
external environment.
✔It allows the entry and exist of some materials ( ions
and molecules ) in and out of the cell.

12. PLASMA MEMBRANE

13. ✔It also prevents the movement of some other
materials.
✔It is a very thin, elastic, living and selective
permeable membrane.
✔It is made up of lipid and proteins.
✔It encloses nucleus and cytoplasm.
✔It helps in protection of cellular component.
How does the movement of substance takes place into
the cell? How do substances move out of the cell?
Some substances like carbon dioxide and oxygen can move
across the cell membrane by a process called diffusion.
In this case there is spontaneous movement of a
substance from a region of high concentration to a
region of low concentration. Thus, diffusion plays an
important role in gaseous exchange between the cells
as well as the cell and its external environment.

14. Osmosis: The movement of water molecules through a
selectively permeable membrane is called osmosis.
Osmosis takes place from a region of high water
concentration to region of low water concentration
through a semi permeable membrane. Thus, osmosis is
a special case of diffusion.
Significance of diffusion:
❑Gaseous exchange between the leaves and air takes
place.
❑Transport of food through phloem takes place.
❑Loss of water from the plants is based on the principle
of diffusion.
❑Movement of ions and solutes from one cell to another
cell takes place through diffusion.

16. Significance of osmosis:
❑Absorption of water by roots and root hairs.
❑Water moves from one cell to another cell.
❑It controls the amount of water within the
cell.
❑It controls various physiological activities :
❖Opening and closing of stomata.
❖Splitting of fruits due to over irrigation.
❖Dehiscence of fruits and seeds for dispersal.

17. HYPOTONIC, ISOTONIC AND
HYPERTONIC SOLUTION
❑Hypotonic solution: If the medium surrounding the cell
has a higher water concentration than the cell,
meaning that the outside solution is very dilute, the
cell will gain water by osmosis ( endosmosis ) .Such a
solution is called hypotonic solution. In this case the
cell is likely to swell up.
❑Isotonic solution: If the medium surrounding the cell
has exactly the same water concentration as the cell,
there will be no net movement of water across the cell
membrane. Such a solution is called isotonic solution.
In this case there is no overall movement of water.
The cell will stay the same size.

20. ❑Hypertonic solution: If the medium surrounding the cell
has a lower concentration of water than the cell,
meaning that it is a very concentrated solution, the
cell will lose water by osmosis ( exo-osmosis ) . Such a
solution is called a hypertonic solution. In this case
the cell will shrink.
Endocytosis: The flexibility of the cell membrane also
enables the cell to engulf in food and other materials
from its external environment. Such a process is known
as endocytosis. Amoeba acquires its food through this
process.
Types of endocytosis:
⮚Phagocytosis: Cell takes in solid food material through
plasma membrane.
⮚Pinocytosis: Cell takes in fluid matter through plasma
membrane.

23. ENDOCYTOSIS

25. Exocytosis: It is the process of exudation of secretions or the
waste materials out of the cell through plasma membrane.
It is opposite of endocytosis.
When the metabolic wastes are thrown out of the cell,
the process is called ephagy.
Cell wall: In plant cells, in addition to the plasma membrane,
there is another rigid outer covering called cell wall. It lies
out side the plasma membrane. In plant cell , cell wall is
mainly composed of cellulose. Cell wall is non-living.
Function of cell wall:
❖It gives a shape to the cell.
❖It helps in giving rigidity to the cell.
❖It gives mechanical strength.
❖It also support the internal structure of the cell.
❖It protects the cell from osmotic bursting.
❖It helps in the expansion of cells.

27. Plasmolysis: When a living plant cell looses
water through osmosis then there is
shrinkage or contraction of the contents
of the cell away from the cell wall. This
phenomenon is called plasmolysis.
Protoplasm: All living components of a cell
is protoplasm. It is clear colourless or
slightly translucent, jelly like, viscous
semi fluid substance. It can be
distinguished into a centrally located
nucleus and cytoplasm.

28. PLASMOLYSIS

29. PLASMOLYSIS

30. ❖Nucleus:
✔It is the largest and most prominent structure of the
cell.
✔Generally one nucleus is present in each cell.
✔Generally present in the centre of younger cell but it
is pushed towards the periphery in the mature cell.
✔It governs the cell that is why it is called controlling
centre of the cell ( governor of the cell ).
✔It is bounded by double layer membrane.
✔The membrane have pore called nuclear pore.
❖Important parts of nucleus:
▪Nuclear membrane.
▪Nucleoplasm.
▪Chromatin network.
▪Nucleolus.

32. ❑Nuclear membrane:
❖It is double layer membrane that separates
nucleoplasm from cytoplasm.
❖It has number of pores which helps in exchange of
materials between nucleus and cytoplasm.
❖It disappears during cell division.
❑Nucleoplasm:
❖The fluid which is present inside the nucleus is called
nucleoplasm/ karyolymph.
❖It is a gel like dense substance present within the
nucleus.
❖In this chromatin material and nucleolus are present.

33. ❑Chromatin net work or chromatin material:
❖It is the entangled mass of thread like structures.
❖During cell division, it is organized to form
chromosomes. Chromosomes are made up of DNA
(deoxyribonucleic acid) and proteins.
❖DNA is the master molecule and it controls all the
activities of the cell. Functional segment of DNA are
called genes. Genes control the characters.
❖On one chromosome many genes are present.
Chromosome are considered as ‘heredity vehicle’ as it
transfers the characters from parent to offspring.

34. ❑Nucleolus:
❖Spherical or oval body present within the nucleus.
❖It is generally bigger in size in those cells which are
actively concerned with protein synthesis.
❖It is more prominent in non-dividing cells.
❖It contains large amount of RNA and protein, also a small
amount of DNA.
Function of nucleus:
⮚It helps in maintenance of cell.
⮚It helps in cell division.
⮚It is needed for inheritance of character from parent to
offspring.
⮚It controls various cytoplasmic activities.

36. ❑Cytoplasm:
❖The fluid which is present inside the cell but outside the
nucleus is called cytoplasm.
❖It is a larger region of each cell enclosed by a cell
membrane.
❖It is transparent, semi solid ground substances in which
various cell organelles are present.
❖Water is the main component of cytoplasm which contains
fats, proteins, carbohydrates and various organic
substances.
❖It helps in exchange of materials between cell organelles.
❖It acts as a site of chemicals reactions like glycolysis.
❖Cytoplasm takes very little stain.

38. CHARACTER PROKARYOTIC CELL EUKARYOTIC CELL
Size Generally small (1-10
micro meter).
Generally large ( 5-100
micro meter).
Nuclear region Not well defined and
not surrounded by a
nuclear membrane &
known as nucleoid.
Well defined and
surrounded by a nuclear
membrane.
Chromosomes Single and circular. More than one and
linear.
Membrane bound
organelles
Absent. Present.
Cell division By simple fission
(amitosis).
By mitosis and meiosis.
Nucleus Lack true nucleus. True nucleus present.
Ribosome Smaller in size and
randomly scattered in
cytoplasm.
Bigger in size and
attached to the
endoplasmic reticulum or
freely present in
cytoplasm.
Example Bacteria and Blue green
algae
Plants, animals and
fungi.

41. CELL ORGANELLES
The membrane bound structures present
in the cytoplasm are called cell
organelles ( mitochondria, chloroplast,
nucleus, endoplasmic reticulum etc.).
The structures which are not bounded by
membranes are called cell inclusions
(ribosome, centriole ).

42. ENDOPLASMIC RETICULUM
❑It consists of an irregular network of channels
which are bounded by membrane and are
interconnected with each other.
❑They are seen with the help of electron
microscope only.
❑If ribosomes are seen attached to their
surface, then they are called rough
endoplasmic reticulum (R.E.R).
❑If ribosomes are not present on endoplasmic
reticulum, they are called smooth endoplasmic
reticulum (S.E.R).

44. ❑FUNCTION OF ENDOPLASMIC RETICULUM:
❖Ribosomes present are the sites of protein
synthesis.
❖The S.E.R helps in the manufacture of fat
molecules or lipids.
❖It helps in the intracellular transport of
substances (proteins).
❖It helps in the synthesis of steroid hormones
(which detoxifying many poisons and drugs).
❖It acts as skeleton system of the cell.

45. Membrane biogenesis:
The S.E.R helps in the manufacture
of fat molecules or lipids,
important of cell function. Some of
these proteins and lipids help in
building the cell membrane. This
process is known as membrane
biogenesis.

46. GOLGI APPARATUS / GOLGI BODIES
❑Discovered by Camillo Golgi.
❑They are the membrane bound (single layer)
structures that occur in the form of tubules,
vesicles or cisternae.
❑They are usually seen aggregated towards the
nucleus.
❑In plants they occur as unorganized and
unconnected channels like structures called
dictyosomes.

48. FUNCTION OF GOLGI BODIES:
❑Helps in the synthesis of some polysaccharides
from simple sugar.
❑Helps in formation of glycoprotein.
❑It is involved in the transformation.
❑Primary lysosomes are formed from
golgibodies by budding.
❑They are responsible for secretion and
transport in the cell.

49. LYSOSOMES
❑They are small sized enzyme containing vesicles which
are bounded by single membrane.
❑During the disturbance in cellular metabolism, for
example when the cell gets damaged, lysosome may
burst and the enzymes digest their own cell.
Therefore lysosomes are also called suicide bags of
the cell.
❑Enzymes present in lysosomes are made by R.E.R.
❑They also destroy the foreign materials which enter
the cell.

51. FUNCTION OF LYSOSOMES:
❑They helps in the digestion of food
within the cell ( intracellular digestion ).
❑They protect the body from bacteria
and other harmful organisms.
❑They help in the removal of old worn out
cell organelles.

52. MITOCHONDRIA
❑They are small bodies that occur in large
numbers.
❑A mitochondrion consists of:
⮚An outer membrane.
⮚An inner membrane.
⮚Inner membrane folded inwards to form the
cristae.
⮚The cristae lie in a ground structure called
matrix.
❑They have their own DNA and ribosomes.

53. MITOCHONDRIA

54. FUNCTION OF MITOCHONDRIA:
Mitochondria have enzymes
necessary for the oxidation of
glucose thus releasing energy in
the form of ATP. They are
therefore called power house of
the cell.

55. PLASTIDS
❑Only present in plant cell.
❑It is of two types: chromoplast (coloured plastid) and
leucoplast (white or colourless).
❑It is a lamellated structure which is bounded by
double membrane.
❑Plastids containing the pigment chlorophyll (green
pigment) are called chloroplast.
❑Chloroplast is important for photosynthesis.
❑Leucoplast stores starch, oil, protein granules.
❑Plastids show two distinct regions: grana and stroma.
❑Plastids have their own DNA and ribosomes.

58. FUNCTION OF PLASTIDS:
❑Chloroplast is called kitchen of the cell
as food is synthesized by the process of
photosynthesis.
❑Chromoplast gives various colours to
different parts of the plant (petals of
flower).
❑Leucoplast stores food.

59. VACUOLE
❑Vacuoles are sac like structure meant for storage of
solid and liquid material.
❑Vacuoles are small sized in animal cells while large
sized in plant cell.
❑In plant cells vacuoles are full of cell sap that
contains amino acids, water, protein, organic acid,
sugar etc. This cell sap provide turgidity and rigidity
to the cell.
❑In unicellular organism like amoeba the vacuole having
food is called food vacuole.
❑The outer membrane of vacuole is called tonoplast.
❑It is osmoregulatory in function.

61. THANKS