For better understanding about human cell and its organelles

1. CELL AND CELL ORGANELLES
PRESENTED BY:
DR.NAVEEN PARVATHAREDDY,
I MDS,
NARAYANA DENTAL COLLEGE, NELLORE, AP.

2. CONTENTS
 INTRODUCTION
 HISTORY
 CLASSIFICATION
 BASIC CELL STRUCTURE
 CELL MEMBRANE
 CYTOPLASM

3.  CELL ORGANELLES - STRUCTURE &
FUNCTIONS
 CYTOSKELETON
 PROJECTIONS FROM CELL SURFACE
 CELL INCLUSIONS
 REFERENCES

4. INTRODUCTION

5. Latin word ‘cella’
Building blocks
Functions
Cell biology

7. History

8. SCIENTIST YEAR DISCOVERY
Robert Hooke 1655 CELL
Brown 1831 NUCLEUS
Schleiden 1838 CELL THEORY
Virchow 1858 “OMNIS CELLULA E
CELLULA”
Miescher 1871 DNA
James Watson & Francis
Crick
1953 Double helix model of
DNA.
Singer & nicholson 1972 Fluid Mosaic model

9. CLASSIFICATION

10. Ex:
animals, plants,
protozoa, and
fungi.
Ex :
Bacteria, blue
green algae

12. Size &shape
• Spindle
shaped
• Small & disc
shape
• Long &
branched
number
• Unicellular
• multicellular
function
• Movement
• Synthesis &
secretion
• Transport
• Digestion
• Absorption
• Growth, repair
Based on cell

13. CELL STRUCTURE

14. CELL
CYTOPLASM NUCLEUSCELL MEMBRANE
 CYTOSKELETON
 CYTOSOL
 CELL ORGANELLES
 CELL INCLUSIONS
 NUCLEAR MEMBRANE
 NUCLEOLUS
 CHROMATIN
 NUCLEOPLASM

15. • Outer limiting membrane
• Thickness
• Functions as
• Other names
HISTORY
• Lipid bilayer
• Sandwich model
• Unit membrane
model
• Fluid mosaic model
Cell membrane:

17.  major constituents of plasma membrane are: lipids, proteins,
carbohydrates.
LIPIDS :
1. Phospholipids
2. Cholesterol.
3. Glycolipids.

19. Membrane Proteins
They are mainly of two types:
Peripheral proteins
Integral proteins

20. Many Functions of Membrane Proteins
Outside
Plasma
membrane
Inside
Transporter
Cell surface
receptorEnzyme
activity
Cell surface
identity marker
Attachment to the
cytoskeleton
Cell adhesion

21. Membrane carbohydrates
Play a key role in cell-cell recognition
 ability of a cell to distinguish one cell from another
 important in organ &
tissue development
 basis for rejection of
foreign cells by
immune system

22. FUNCTIONS OF PLASMA
MEMBRANE:It maintains the
shape of cell
Helps in
absorption of
nutrients
Acts as
Semipermeable
membrane
Acts as Receptors for
hormones &
enzymes
Regulates various
metabolic reactions
Helps in adhesion
between cells
Helps in exchange
of gases

23. Molecules move through
plasma membrane by:
 Passive transport
a) Diffusion
b) Facilitated diffusion
c) Osmosis
 Active transport

24. Diffusion
 Move from HIGH to LOW concentration
 No energy needed.
diffusion

25. Diffusion through phospholipid bilayer
molecules that can get through
directly are fats & other lipids
inside cell
outside cell
lipid
salt
aa H2Osugar
NH3
 molecules can NOT
get through
polar molecules
H2O
Ions
salts, ammonia
large molecules
starches, proteins

26. Channels through cell membrane
 Membrane becomes semi-permeable with protein channels
 specific channels allow specific material across cell
membrane
inside cell
outside cell
sugaraaH2O
saltNH3

27. Facilitated Diffusion
 Diffusion with the aid of protein channels or
carrier proteins.
 No energy is needed.
open channel = fast transport
high
low

28. CARRIER PROTEINS:
The proteins move specific type of molecules through the
membrane from one side to other side of membrane.

29. Active Transport
Cells may need to move molecules against
concentration gradient.
Protein “pump”
“costs” energy = ATP
conformational change
ATP
low
high

30. Transport summary
simple
diffusion
facilitated
diffusion
active
transport
ATP

31. Transport of large molecules (bulk
transport)
Endocytosis
Phagocytosis
Pinocytosis
Exocytosis

32. Phagocytosis:
 cell eating
 Actin dependent endocytosis

33. Pinocytosis
 cell drinking
 endothelium
 clathrin independent endocytosis

34. EXOCYTOSIS
It is the process by which a vesicle moves from
cytoplasm to the plasma membrane where it
discharges its contents to the extracellular space.

35. CYTOPLASM

36.  It is everything that is
present between the cell
membrane and the
nuclear envelope.
 consists primarily of
water.
 It includes:
 Factory area of cell
 site for

37. CYTOSOL
The cyoplasmic matrix is a
concentrated aqueous gel consisting
of molecules of different sizes and
shapes.
Such as electrolytes, metabolites,
RNA, and synthesised proteins.

38. Cytoplasmic cell Organelles
 Membranous organelles
 Mitochondria
 Golgi apparatus
 Rough surfaced endoplasmic reticulum
 Smooth surfaced endoplasmic reticulum
 Coated vesicle
 Secretory vesicles
 Lysosomes
 Endosomes / Peroxisomes
 Non Membranous organelles
 Ribosomes
 Microtubules
 Filaments

39. CELL ORGANELLES

40. MITOCHONDRIA-“powerhouse of the cell”
 Bilayered
organelle
 “CRISTAE”.
 “MATRIX”.

41.  The outer membrane possess
receptors
 The inner membrane contains
several enzymes, including
phospholipase A2, monoamine
oxidase and acetyl coenzyme A
(coA) synthase.
 Matrix contains
 Elementary particles

42.  The membrane forming the cristae contains proteins that have
three major functions :
1.oxidative electron transfer.
2. Synthesis of ATP.
3.Regulating transport of metabolites .

43.  CISTERNAE
 Two types:
r ER
s ER
 Present
abundantly in
 RER and
Ribosomes are
concerned with
protein
synthesis.
ENDOPLASMIC RETICULUM

44. Functions of rER:
 Segregation of proteins.
 Helps in initial glycosylation
of glycoproteins.
 Synthesis of phospholipids.
 The assembly of multi chain
protein
 Major reservoir of ca ions.
Functions of sER:
 Lipid and steroid
synthesis
 Detoxification of drugs

45.  Camillo Golgi.
 Usually composed of 4 or more stacked layers of thin,
flat, enclosed vesicles lying one side of nucleus.
 Prominent in secretory cells.
 It functions in association with ER,
GOLGI COMPLEX

46. STRUCTURE
 Functionally Golgi complex is
divided into 3 regions
1. The region nearest the nucleus is
cis-face
2. The opposite face, nearest to cell
membrane is trans-face
3. The intermediate part is medial
Golgi.

47.  Cis face: proteins are
phosphorylated
 Medial golgi : protein –
carbohydrate complexes
formed
 Trans face : Inactive forms to
active forms
 Sugar residues are added
and then
 Sorting & packing into
vesicles is done.

48. LYSOSOMES
(Digestive bags, suicide sacks)
 Lysosomes have unique membrane that is resistant to acidic
internal PH.
 They are fomed from region of golgi complex.
 They are membrane limited vesicles and contain large variety
of hydrolytic enzymes.
 They are abundant in cells exhibiting phagocytic activity
 Digestive organ of cell

50. Functions:
 Contains enzymes essential for for
intracellular digestion.
 Kill and remove foreign bodies.
 Acrosome
 Autolysis.

51. PEROXISOMES
single membrane bounded organelles with
oxidative enzymes
Structure similar to lysosomes
Formed by self replication or by budding
off from sER
Detoxifying organs of cell
Lipid metabolism, myelin synthesis
Abundant in hepatocytes

52. The enzymes in them react
with other substances and
produces H2O2 which is
used to detoxify various
substances by oxidising
them.
ZELLWEGER SYNDROME

53. RIBOSOMES
• Made up of a large and a
small subunit.
• Ribosomes are seen in
1.bound form
2.free form
• Mainly involved in
protein synthesis

54. STRUCTURE
 RNA molecules of both subunits are synthesized with in the
nucleus
 The individual ribosomes held together by strand of mRNA to
form poly ribosomes.
 The message carried by mRNA is a code for the amino acid
sequence of proteins being synthesized by a cell and the
ribosomes play a crucial role in decoding or translating this
message during synthesis.

56.  Centrosome is the area located
near nucleus.
 The two centrioles are located
perpendicular to each other in the
centrosome.
 Each centrioles consists of nine
bundles of tiny microtubules
arranged in a circle.
 Functions:
1. Basal body formation
2. Mitotic spindle formation
Centrosome:

57. CYTOSKELETON

58. The cytoplasm is permeated by a number of
fibrillar elements that collectively form a
supporting network called the cytoskeleton.
Functions of cytoskeleton:-
 Maintains the cellular architecture
 Cell motility
 Divides cytosol into functionally discrete areas
 Anchoring cells to each other.

60.  25nm
 Protein is tubulin dimer(α and β
subunits).
 Polymerisation of microtubles
in centrioles constitute the
microtubule organising centre
(MTOC).
 Act as conveyor belts
ROLE:
 Intra-cellular vesicular
transport.
 Movement of cilia and
flagella.
 Mitotic spindles
 Cell elongation and
movement.
Microtubules

61. Microfilaments
 Diameter is 5 nm.
 It is composed of actin filaments.
Free actin = G –actin
polymerised actin = F-actin.
FUNCTIONS:
 Anchorage and movement of
membrane protein
 Formation of core of microvilli.
 Cell division, locomotion.
 Extension of cell processes.

62. Intermediate filaments
 Diameter: 10nm
 Connects adjacent cells through
desmosomes
 Made of fibrous proteins.
Proteins:
Cytokeratin in epithelial cells
Neurofilament proteins in neurons
Desmin in muscle
Glial fibrillary acidic protein in astrocytes
Laminin in nuclear lamina
Vimentin in various cells

63. PROJECTIONS FROM CELL SURFACE
1. CILIA:
 These are
minute hair-like
projections from
free surface of
some cells.
 0.25μm in
diameter.
 They are made
up of
microtubules.

65. FUNCTIONS:
Ciliary action moves :-
-Secretions in the respiratory tract
-Ova through the uterine tube.
-Spermatozoa through the male genital tract
-Cells in embryogenesis
 Abnomalities in cilia can lead to primary ciliary
dyskinesia(PCD) or immotile cilia syndrome.

66. 2) FLAGELLA
 Similar in structure to cilia but longer.
Eg; tail of spermatozoan.
 Movement starts at base of flagellum.
nearest segment--- one direction.
succeding segements--- opposite direction .
wave like motion passes down the flagellum.

67. 3) MICROVILLI:
 With EM: Finger like extensions of cell membrane.
 plasma memebrane and numerous actin filaments in it.
 Increases the surface area for absorption of materials

68. CELL INCLUSIONS

70.  Inclusions contain products of metabolic activity of the cell
 Consists of pigment granules, lipid droplets and glycogen.
 Considered as nonmoving and nonliving components of the cell.
 characteristic staining properties

71. Commonly seen inclusions are
 Lipofuscin
 Hemosiderin
 Glycogen
 Lipid inclusions
 Crystalline inclusions

72. LIPOFUSCIN
 Brownish gold pigment –H & E.
 conglomerate of lipids, metals & organic molecules.
 wear and tear pigment.
HEMOSIDERIN :
 Iron storage complex found in cytoplasm.
 LM-deep brown granule.

73. GLYCOGEN:
 Highly branched polymer.
 may not be stained in H & E.
 Liver and striated muscle cells shows unstained regions where
glycogen is present.
 In EM clusters of granules of 25 to 30nm.

74. LIPID INCLUSIONS:
 Are usually nutritive inclusions that provide energy for cellular
metabolism.
 May appear in cell for very short time but in Adipocytes they
constitute most of cytoplasmic volume and compress other
organelles into thin rim at margin of the cell.
CRYSTALLINE INCLUSIONS:
 These contained in certain cells are recognised in light
microscope. In humans are found in sertoli and leydig cells of
testis may contain storage material or cellular metabolite.
 Significance is not clear.

75. REFERENCES:
 TEXT BOOK OF MEDICAL PHYSIOLOGY- GUYTON
& HALL 12TH EDITION
 CELL & MOLECULAR BIOLOGY- NALINI CHENDAR
& VISELLI
 BASIC HISTOLOGY- JUNQUERA
 HISTOLOGY 9TH EDITION- HAMS
 TEXT BOOK OF HUMAN HISTOLOGY, 4TH EDITION
– INDERBIR SINGH
 HISTOLOGY, A TEXT & ATLAS,5TH EDITION-
MICHAEL H.ROSS,WOJCIECH PAWLINA

76. THANK YOU