Cells are the basic units of organisms and can only be observed under a microscope. The document then discusses the basic structures of cells including the cell membrane, nucleus, cytoplasm, and various organelles. It explains the functions of these structures and how they allow cells to intake nutrients, produce energy, synthesize proteins, and remove waste. The document also covers cellular processes like diffusion, osmosis, endocytosis, and exocytosis that allow movement of materials into and out of cells.

3. 3
Introduction to CellsIntroduction to Cells
Cells are the basic units of organisms
Cells can only be observed under microscope
Basic types of cells:
Animal Cell Plant Cell Bacterial Cell

4. 4
Basic Structure of a Cell

5. Cells
• Smallest living unit
• Most are microscopic

6. 6
Eyepiece
Fine adjustment
Arm
Stage
Condenser
control knob
Base
Body tube
Coarse
adjustment
Iris diaphragm
Revolving
nosepiece
Objective
Clip
Condenser
Mirror
Parts of Compound Microscope

7. Discovery of Cells
• Robert Hooke (mid-1600s)
– Observed sliver of cork
– Saw “row of empty boxes”
– Coined the term cell

8. Cell theory
• (1839)Theodor Schwann & Matthias Schleiden
“ all living things are made of cells”
• (50 yrs. later) Rudolf Virchow
“all cells come from cells”

9. Principles of Cell Theory
• All living things are made of cells
• Smallest living unit of structure and
function of all organisms is the cell
• All cells arise from preexisting cells
(this principle discarded the idea of
spontaneous generation)

10. Characteristics of All Cells
• A surrounding membrane
• Protoplasm – cell contents in thick fluid
• Organelles – structures for cell function
• Control center with DNA

11. Cell Size

12. 12
The cell is the Basic Unit ofThe cell is the Basic Unit of
LifeLife
• Cell is the smallest unit of living organisms
• Unicellular organisms are made of one cell only
• The cells of multicellular organisms are
specialized to perform different functions
–e.g. mesophyll cells for photosynthesis and
root hair cells for water absorption

13. 13
Levels of organizationLevels of organization
• Cells are grouped
together and work
as a whole to
perform special
functions

14. 14
TissueTissue
• A group of similar cells to perform
a particular function
–Animals : epithelial tissue,
muscular tissue
–Plants : vascular tissue,
mesophyll

15. 15
Number of Cells
Organisms may be:
• Unicellular – composed of
one cell
• Multicellular- composed
of many cells that may
organize

16. 16
OrganOrgan
• Different tissues group together to
carry out specialized functions
– Heart : consists of muscles, nervous
tissue and blood vessels
– Leaf : consists of epidermis,
mesophyll and vascular tissue

17. 17
Stoma
Air Space
Spongy Mesophyll
Cell
Chloroplast
The Structures of a Leaf
(Plant Organ)
Palisade
Mesophyll Cell

18. 18
The Structures of a Heart (Animal Organ)

19. 19
Organ SystemOrgan System
• Several organs and tissues work together
to carry out a particular set of functions in
a co-ordinated way
– Human : digestive, respiratory, excretory,
circulatory and reproductive systems
– Plant : root and shoot systems

20. 20
Human Body SystemsHuman Body Systems
Examples of systems :
 Digestive System
 Respiratory System
 Circulatory System
 Nervous System
 Reproductive System

21. Human digestive system
Examples of a Human Body System

22. 22
The RespiratorySystem

23. Human circulatory system

24. Human nervous system

25. 25
Levels of OrganizationLevels of Organization
 TISSUES (muscle, epithelium)
 ORGANS (heart, lungs, stomach)
 SYSTEMS (circulatory system)
 CELLS (muscle cells,nerve cells)
 ORGANISM (human)

26. 26
 Prokaryotes include bacteria
& lack a nuclear membrane or
membrane-bound structures
called organelles
Eukaryotes include most
other cells & have a nucleus
and membrane-bound
organelles (plants, fungi, &
animals)
Cells May be Prokaryotic or Eukaryotic

27. 27
Prokaryotes
• Consists of Prokaryotic cells
do not have a nuclear
membrane. The nuclear
material a single chromosome
and lies in the cytoplasm.
• The nuclear region in the
cytoplasm is called nucleoid.
• Membrane-bound organelles
are absent.
• Prokaryotic cells are found in
bacteria and cynobacteria (blue-
green algae).

28. What Prokaryotic and Eukaryotic Cells Have in
Common
• Both have DNA as their genetic material (it’s
DNA that tells cells what kind of cells they
should be).
• Both are covered by a cell membrane.
• Both contain RNA.
• Both are made from the same basic chemicals:
carbohydrates, proteins, nucleic acid, minerals,
fats and vitamins.
• Both have ribosomes (the structures on which
proteins are made).
• Both regulate the flow of the nutrients and
wastes that enter and leave them.
• Both have similar basic metabolism (life
processes) like photosynthesis and
reproduction.
• Both require a supply of energy.

30. Eukaryotic cell
1.Cells that have a
membrane around their
nucleus.
2.Cells usually are 10 times
larger than Prokaryote
cells.
3. They have membrane
bound cell organelles
4.They have more than one
chromosome

31. Representative Animal Cell

32. Representative Plant Cell

33. Plant cells, in addition to
the plasma membrane,
have another rigid outer
covering called the cell
wall.
The cell wall lies outside
the plasma membrane.
The plant cell wall is
mainly composed of
cellulose.
Cellulose is a
complex substance and
provides structural
strength to plants.
.

34. Cell Wall Differences
• Plants – mostly cellulose
• Fungi – contain chitin

35. Plasmolysis
• Plasmolysis of Plant Cells
Plant cells are surrounded by rigid
cell walls. When plant cells are
exposed to hypertonic
environments, water rushes out of
the cell, and the cell shrinks away
from the rigid wall, resulting in
plasmolysis. The plasmolyzed cells
are dehydrated and lose most or all
physiological functions while in the
shrivelled state. If cells are returned
to isotonic or hyptonic
environments, water reenters the
cell and normal functioning may be
restored.

36. Plasma membrane
• This is the outermost covering
of the cell that separates the
contents of the cell from its
external environment.
• The plasma membrane allows
or permits the entry and exit of
some materials in and out of
the cell.
• It also prevents movement of
some other materials.The cell
membrane, therefore, is called
a selectively permeable
membrane.

37. Diffusion
• Simple Diffusion - water, oxygen and other molecules move from
areas of high concentration to areas of low concentration, down a
concentration gradient
• for example, some substance like CO2 (which is cellular waste and requires to
be excreted out by the cell) accumulates in high concentrations inside the
cell. In the cell’s external environment, the concentration of CO2 is low as
compared to that inside the cell. As soon as there is a difference of
concentration of CO2 inside and outside a cell, CO2 moves out of the cell, from
a region of high concentration, to a region of low concentration outside the
cell by the process of diffusion.
• Similarly, O2 enters the cell by the process of diffusion when the level or
concentration of O2 inside the cell decreases. Thus, diffusion plays an
important role in gaseous exchange between the cells as well as the cell and
its external environment.

38. Diffusion
• Molecules move to equalize concentration

39. Diffusion
• Move from HIGH to LOW concentration
– “passive transport”
– no energy needed
diffusionS osmosis
movement of water

40. Diffusion across cell
membrane
• Cell membrane is the boundary between
inside & outside…
– separates cell from its environment
IN
food
carbohydrates
sugars, proteins
amino acids
lipids
salts, O2, H2O
OUT
waste
ammonia
salts
CO2
H2O
products
cell needs materials in & products or waste out
IN
OUT
Can it be an impenetrable boundary? NO!

42. OSMOSIS
• Two solutions of equal solute concentration are
termed “isotonic”
– Water concentration is also equal
• Two solutions of unequal solute concentration
are not isotonic
– Solution with more solute is “hypertonic”
• More solute = less water
– Solution with more solute is “hypotonic”
• Less solute = more water
)

43. Unicellular freshwater organisms and
most plant cells tend to gain water through
osmosis. Absorption of water by plant roots
is also an example of osmosis

44. Concentration of water
• Direction of osmosis is determined by
comparing total solute concentrations
– Hypertonic - more solute, less water
– Hypotonic - less solute, more water
– Isotonic - equal solute, equal water
hypotonic hypertonic
water
net movement of water

45. Endocytosis
The flexibility of the cell membrane
also
enables the cell to engulf in food and
other material from its external
environment. Such processes are
known as endocytosis.
Amoeba acquires its food through such
processes.

46. Process of Endocytosis
• Plasma membrane surrounds material
• Edges of membrane meet
• Membranes fuse to form vesicle

47. Forms of Endocytosis
• Phagocytosis – cell eating
• Pinocytosis – cell drinking

48. Exocytosis
• Reverse of endocytosis
• Cell discharges material

49. Exocytosis
• Vesicle moves to cell surface
• Membrane of vesicle fuses
• Materials expelled

50. PHAGOCYTOSIS
• Material is surrounded by pseudopodia
• Pseudopodia fuse
• Material is engulfed, enclosed within a
membrane-bound structure (vesicle, vacuole)

51. freshwater balanced saltwater
Managing water balance
• Cell survival depends on balancing water
uptake & loss

54. Nucleus
• Control center of cell
• Double membrane
• Contains
– Chromosomes
– Nucleolus

55. Separates nucleus
from rest of cell
Double membrane
Has pores

56. The nucleus contains
chromosomes,which are visible
as rod-shaped structures only
when the cell is about to divide.
Chromosomes arecomposed of
DNA and protein
DNA molecules contain the
information necessary for
constructing and organising
cells.
Functional segments of DNA are
called genes.

57. Chromain & chromosomes
• In a cell which is not
dividing, this DNA is
present as part of
chromatin material.
• Chromatin material is
visible as entangled
mass of thread like
structures.
• Whenever the cell is
about to divide, the
chromatin material
gets organised into
chromosomes.

58. Chromosomes during cell
division

59. Nucleolus
• Cell may haveCell may have 1 to 31 to 3
nucleolinucleoli
• Inside nucleusInside nucleus
• DisappearsDisappears when cellwhen cell
dividesdivides
• Makes ribosomesMakes ribosomes thatthat
make proteinsmake proteins

60. Nucleoid
In some organisms like bacteria, the
nuclear region of the cell may be
poorly defined due to the absence of
a nuclear membrane. Such an
undefined nuclear region containing
only nucleic acids is called a
nucleoid.
Such organisms, whose cells lack a
nuclear membrane, are called
prokaryotes

61. Reproduction in Unicellular
organisms
• The nucleus
plays a central
role in cellular
reproduction,
the process by
which a single
cell divides and
forms two new
cells

62. CYTOPLASM
Cytoplasm has various cell organelles

63. Endoplasmic Reticulum
Endoplasmic reticulum (ER) is
an extensive, interconnected,
membranebound network of
tubes and sheets.
The ER membrane is
similar in structure to the
plasma membrane.
It is of two types
1. Rough Endoplasmic Reticulum
(RER)
Ribosomes are attached to the
surface
2.Smooth Endoplasmic Reticulum
(SER)
Ribosomes are not attached to
the surface

64. Functions of endoplasmic
reticulum
• RER synthesizes
Proteins
• The SER helps in the
manufacture of fat
molecules, or lipids,
• Some of these proteins
and lipids help in building
the cell membrane. This
process is known as
membrane biogenesis.
• Some other proteins and
lipids function as
enzymes and hormones.

65. Golgi complex
• The Golgi apparatus, first
described by Camillo Golgi.
• It consists of a system of
membrane-bound vesicles
arranged approximately parallel
to each other in stacks called
cisterns.
• These membranes often have
connections with the
membranes of ER and
therefore constitute another
portion of a complex cellular
membrane system.

67. Function of Golgi apparatus
• It is like a cellular post office-The
material synthesised near the ER
is packaged and dispatched to
various targets inside and
outside the cell through the Golgi
apparatus
• Involved in the formation of
lysosomes.
• It also helps in formation of
complex sugars from simple
sugars.

68. Lysosomes
• Lysosomes are
Membrane bound
sacs filled with
powerful
digestive
enzymes. These
enzymes are
manufactured by
RER.Role and
function of
lysosomes

69. Lysosomes- functions
• : 1 As Waste disposal system of the cell
• : Lysosomes are the cells' garbage disposal
system. Any foreign material such as
bacteria that enters a cell and worn out cell
organelles are engulfed by lysosomes
and broken down.
• 2, Digestive bags of the cell
• : Since lysosomes are little digestion
machines, they go to work when the
cellabsorbs or eats some food. Once the
material is inside the cell, the lysosomes
attach and release their enzymes. The
enzymes break down complex molecules
that can include complex sugars and
proteins. food is scarce and the cell is
starving, the lysosomes go to work even if
there is no food for the cell. Whenthe signal
is sent out, lysosomes will actually digest
the cell organelles for nutrients.
• 3.Suicide bags of the cell
• : Sometimes, when the cell gets damaged,
the lysosomes burst and the enzymesdigest
their own cell, so they are also called suicide
bags of the cell.

70. Mitochondria
Mitochondria have two membrane
coverings. The outer membrane is
smooth while the inner membrane
is deeply folded.
These folds create a large surface
area for ATP-generating chemical
reactions.
The folds of inner membrane are
said to be cristae

71. Mitochondria -functions
Mitochondria are known as the powerhouses
of the cell. The energy required for various
chemical activities needed for life is released
by mitochondria in the form of ATP
(Adenosine triphopshate) molecules.
ATP is known as the energy currency of the
cell.The body uses energy stored in ATP
for making new chemical compounds and
for mechanical work

72. Mitochondria – semi
autonomous cell organelle
• Mitochondria are
strange organelles in
the sense that they
have their own DNA
and ribosomes.
• Therefore,
mitochondria are able
to make some of their
own proteins.

73. Plastids
• Plastids are present
only in plant cells.
There are three
types of plastids
• 1. Chromoplast-
Coloured plastid
• 2. Leucoplast `
Colourless plastid
• 3. Chloroplast-
Green plastid

74. Chromoplast
• Chromoplasts are red, yellow or orange
in colour and are found in petals of
flowers and in fruit. Their colour is due
to two pigments, carotene and
xanthophyll
the primary function in the cells of flowers is to attract agents
of pollination, and in fruit to attract agents of dispersal.

75. Leucoplasts
• Leucoplasts are colourless plastids
and occur in plant cells not exposed to
light, such as roots and seeds. They
are colourless due the absent of
pigments.
• Functions
• They store carbohydrates, fats&
proteins

76. Chloroplast
• Chloroplasts are usually disc-
shaped and surrounded by a
double membrane. Inside the
inner membrane there is a watery
protein-rich ground substance or
stroma
• in which is embedded a
continuous membrane system,
the granal network. This network
has membrane-bound vesicles
called thylakoids.
• The thylakoids usually lie in
stacks called grana and contain
the photosynthetic pigments -
green chlorophyll a and b and the
yellow to red carotenoids.
• The grana are interconnected by
tubular membranes called the
stroma lamellae.
Chloroplasts serve as the site of photosynthesis

77. Chloroplast – semiautonomous
cell organelle
Plastids are similar to
mitochondria in
external structure.
Like the mitochondria,
plastids also have their
own DNA and
ribosomes

78. Ribosomes
• Location
• 1. Cytoplasm
• 2. On the surface
of the RER
• Function
Protein synthesis

79. Vacuole
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.

80. Functions of vacuole
• In plant cells vacuoles are full of cell sap
and provide turgidity and rigidity to the cell.
• Many substances of importance in the life of
the plant cell are stored in vacuoles. These
include amino acids, sugars, various organic
acids and some proteins.
• In single-celled organisms like Amoeba, the
food vacuole contains the food items that the
Amoeba has consumed.
• In some unicellular organisms,specialised
vacuoles also play important roles in expelling
excess water and some wastes from the cell.
Amoeba
Paramoecium

81. Centrioles
• Seen in animal cells
• Play a role in cell division

82. Differences between Animal cell & Plant cell

83. Differences between Animal cell & Plant cell