Prokaryotic cell structure and Properties Eukaryotic cell structure and Properties

1. PROPERTIES OF CELLS AND
CELL MEMBRANE
Dr. Pulipati Sowjanya
Professor & Head
Vignan Pharmacy College
Vadlamudi, Guntur (Dt)

2. The Discovery of Cells
All living things are made up of one or more cells.
• A cell is the smallest unit that can carry on all of the
processes of life.
Hooke
– In 1665, Robert Hooke discovered cells in slices of cork.
• Leeuwenhoek
– In 1673, Anton van Leeuwenhoek was the first to observe living cells in
microorganisms;
Leeuwenhoek called these organism animalcules~ we now call them
protists.

3. Cell Diversity
Cell Shape
– A cell’s shape reflects its function.

4. Cell Diversity
Cell Size
– Cell size is limited by a cell’s surface area–to volume ratio.

5. Cell Diversity
Cell Size
• Unicellular organisms are made up of one cell
• Multicellular organisms are made up of many cells that often
specialize according to function - differentiation

6. OVERVIEW OF CELL STRUCTURE
https://www.youtube.com/watch?v=URUJD5NEXC8&t=278s

7. Prokaryotic Cells
Cells lack a nucleus and
membrane bound organelles
-Includes bacteria
-Single, circular chromosome in
nucleoid region
-Surrounded by cell membrane
and a cell
wall made up of peptidoglycan

8. PROKARYOTE STRUCTURES
1. Appendages- flagella, pili, fimbrae
2. Cell envelope- glycocalyx, cell wall ,
cell membrane
3. Cytoplasm- ribosomes,
granules,
nucleoid/chromosome.

9. BACTERIAL APPENDAGES:
• Pili (pl), pilus (s)
–
–
only found in gram negative bacteria
tubulare, hairlike structures of protein larger
and more rare than fimbriae.
•
-
-
2 types of pili
attachment pilus - allow bacteria to attach to
other cells
sex pilus, - transfer from one bacterial cell to
another- conjugation.

10. FIMBRIAE
• fimbriae (pl) fimbria (s)
– Adhesion to cells and surfaces
– Responsible for biofilms.
– Pathogenesis of gonococcus and E.coli
Escherichia
coli.

11. FLAGELLA
• Flagella (pl), flagellum(s)
– long appendages which rotate by means of a "motor"
located just under the cytoplasmic membrane.
– bacteria may have one, a few, or many flagella in
different positions on the cell.
• Advantages
- chemotaxis - positive and negative.
- motility
• All spirilla, half of bacilli, rare cocci.

12. FLAGELLA

13. FLAGELLA
Three morphological
regions
•
–
–
Helical filament
long outermost region; composes up to 90% of its length
contains the globular (roughly spherical) protein flagellin
arranged in several chains and form a helix around a hollow
core
–
• Hooked or curved area
filament is attached; consists of a different protein
•
–
–
–
Basal body
terminal portion of the flagellum
fix the flagellum to the cell wall and plasma membrane
composed of a central rod inserted into a series of rings
Gram negative - 2 pairs of rings
•
•
Outer pair - fixed to the outer membrane and
peptidoglycan layer
Inner pair - fixed to the plasma membrane (SM ring)
Gram positive - only inner pair is present

14. MOTILITY
•
–
–
–
Types of bacterial motility
run or swim - when a bacterium moves in one direction
for a length of time
tumbles - periodic, abrupt random changes in direction
swarming - rapid wavelike growth across a solid culture
medium
•
Mechanism of flagellar movement - relative rotation
of the rings in the basal body of the flagellum
Antigenicity
–
flagellar or H antigen - useful in the serological
identification of serotypes of Salmonella organisms

15. ARRANGEMENTS
• Flagella vary in number and arrangement.
• Polar arrangment
– Monotrichious - 1 flagellum at one end
• Fastest; Pseudomonas -example
– Lophotrichious - tuft at one end
– Amphitrichious- bipolar
– Peritrichious - multiple flagella; randomly
dispersed around the bacterial cell
• E. coli - example

16. FLAGELLAR ARRANGEMENTS
A. Monotrichous
B. Lophotrichous
C. Amphitrichous
D. Peritrichous
E. Atrichous

17. AXIAL FILAMENTS

18. AXIAL FILAMENTS
•
tuft of fibrils that arise at the ends of
the cell under the outer membrane
and spiral around the cell
•
rotation an opposing of the outer
membrane movement that propels
the spirochetes by causing them to
move like corkscrews
Found in Spirochetes and are similar
to flagella, but are located between
the cell wall and an outer membrane,
and are attached to one end of the
organism.

19. EVIDENCE OF MOTILITY
Two ways by which motility can be demonstrated:
• direct or microscopic
– hanging drop preparation or wet mount preparation by dark field
mycroscope
– Distinguishes:
• Brownian movement - when the bacteria show molecular
movement
• true motility - if a bacterium describes a rotatory,
undulatory or sinuous movement
• indirect or macroscopic
– Stab inoculation of the semisolid media
• nonmotile - growth is limited at the point of inoculation
• motile - growth is diffuse or moves away from the line of
inoculation; turbidity of the medium

20. DETECTION OF MOTILITY
• Direct • Indirect
Presence mobile
bacteria

21. 2. BACTERIAL SURFACE STRUCTURE
- cell envelope
A. Glycocalyx - some extracellular material
secreted by many bacterial cells in the form of:
a. capsule - attached tightly to the bacterium and has
definite boundaries.
b. slime layer - loosely associated with the bacterium
and can be easily washed off
Compositions:
-
-
layer of polysaccharide
proteins - sometimes

23. FUNCTIONS OF THE CAPSULE
• Protection
• Identification
• Vaccine preparation
• Tissue attachment
• Antibiotic barrier

24. MEDICAL IMPORTANCE -
rapid serological identification of:
• Several groups of streptococci
• Meningococcus
• Hemophilus influenzae
• Klebsiella pneumoniae
• Some of the coliforms
• Yersinia and Bacillus specie

25. CELL WALL
peptidoglycan (polysaccharides + protein)
Components of the peptidoglycan layer:
–
–
– Repeating glycan chains (N acetyl
glucosamine and N acetyl muramic acid)
a set of identical tetrapeptide side chains
attached to N- acetylmuramic acid
a set of identical peptide cross bridges

26. PEPTIDOGLYCAN

27. DIFFERENCES IN CELL WALL STRUCTURE
• Basis of Gram Stain Reaction
– Hans Christian Gram- 1884
• Differential Stain
– Gram Positive vs Gram Negative Cells
• Gram Positive Cells-
– Thick peptidoglycan layer with embedded teichoic
acids
• Gram Negative Cells-
– Thin peptidoglycan layer, outer membrane of
lipopolysaccharide.

28. GRAM STAIN REACTION
• Hans Christian Gram- 1880s
• Divides bacteria into 2 main groups-
– Gram positive
– Gram negative
• Also- gram variable
• Gram nonreactive
• Gram positive bacteria
– many layers of peptidoglycan and teichoic acids.
– form a crystal violet-iodine-teichoic acid complex
• Large complex, difficult to decolorize

29. GRAM POSITIVE BACTERIA

30. • Gram negative bacteria
– Very thin peptidoglycan
– No teichoic acids
– Alcohol readily removes the crystal violet.
– Alcohol also dissolves the lipopolysaccharide of the cell wall.
• Gram variable cells
– Some cells retain crystal violet; some decolorize and take up the
safranin
– 4 factors-
• Genetics- variable amount of teichoic acid.
• Age of culture- older cultures have variable
amount of teichoic acid
• Growth medium- necessary nutrients not available
• Technique-
– smear not thin or evenly made.
– Staining procedure not done correctly- decolorizer left on too long.
GRAM STAIN REACTION

31. GRAM NEGATIVE BACTERIA

33. GRAM STAIN TECHNIQUE

34.  Maintenance of the shape (due to rigidity of
peptidoglycan).
 Protects the cytoplasmic membrane cell
contents
 Rigidity
 Cell wall is osmotically insensitive
 Hypotonic solution – cell burst.
 Hypertonic solution – cell shrank.
 Isotonic solution – bacteria is life.
Function of Cell Wall

35. Cell membrane
Peripheral
Membrane
Protein
Integral
Membrane
Protein
Peripheral
Membrane
Protein
Phospholipid

36.  Selective permeability to different
molecules.
 Active transport aided by permease.
 Play a role in DNA replication.
 Cell wall biosynthesis.
 Mesosomes ----- cell division.
Function of Cytoplasmic Membrane

37. Eukaryotic Cell

38. CELL MEMBRANE

40. FUNCTIONS OF CELL MEMBRANE
 The prime functions of the cell surface membrane are:
 To control what substances can enter and leave the cell -
like passport / border control the cell surface membrane is
a selectively permeable barrier.
 To sense the environment.
 Chemicals can pass through the cell membrane by one of
the following processes:
 Passive diffusion - passive since it requires no energy
expenditure by the cell, two main types:
 Active transport / pumping - uses energy supplied by the
cell, e.g. in the form of ATP.

45. CELL TRANSPORT
https://www.youtube.com/watch?v=ufCiGz75DAk

46. Endoplasmic Reticulum
It is originated from outer membrane of nuclear
membrane . It is of two types - the rough endoplasmic
reticulum (RER), the smooth endoplasmic reticulum
(SER).
The RER consists of interconnected membranous sacs
(cisternae) - unit membrane enclosing a fluid-filled
lumen. The function of the RER is the synthesis,
storage and transport of proteins around the cell. The
proteins are manufactured by the ribosomes, that
stud the outside the RER cisternae.
The RER is continuous with the smooth endoplasmic
reticulum (SER) - a network of branching
membranous tubes that may fill much of the
cytoplasm. The SER is responsible for the synthesis,
storage and transport of lipids and carbohydrates and
also the storage of calcium ions.

47. Golgi Complex/ Apparatus

48. Golgi Complex/ Apparatus
The Golgi apparatus (Golgi body or Golgi complex) is the cell's 'post office'. It consists of
stacks of 4-8 fluid-filled membranous disc-like sacs (cisternae, singular cisterna).
The Golgi apparatus above has been sectioned down the middle. One face (the cis) face
points towards the nucleus and RER (the top face in this diagram).
Fluid-filled spherical membranous globules, called vesicles, bud-off from the RER,
carrying synthesised proteins as cargo.
These vesicles travel to the cis-face of the Golgi complex and fuse with it, delivering their
protein cargo (along with the lipids from the membrane of the vesicle).
Inside the Golgi cisternae the proteins (and lipids) are sorted and labeled by attaching
carbohydrate chains (chains of sugar molecules bonded together) to the proteins (a
process called glycosylayion).
The proteins and their attached carbohydrate chains may also be sulphated - sulphur
may be added to them, giving them a negative charge. They may also
be phosphorylated (by addition of phosphate).
These carbohydrates may be required for the final function of the protein (now a
glycoprotein, protein + carbohydrate chain = glycoprotein) or they may serve as address
labels.

49. Nucleus
It is enclosed in a double unit membrane -
the nuclear envelope (NE). The nuclear
envelope is continuous with the endoplasmic
reticulum (ER). The nuclear envelope
encloses the nuceloplasm. The nucleoplasm is
mostly occupied by chromatin.
Each chromosome consists of a single DNA
molecule coiled around proteins
called histones. The nuclear
envelope is perforated by pores
called nuclear pores. The nuclear pores
allow materials to enter and exit the nucleus

50. Ribosomes
Ribosomes are factories that manufacture
proteins for cells. They are small (diameter
about 10 nm or 10 millionths of a
millimetre) ribonucleoprotein enzymes. A
ribonucleoprotein is a structure consisting of
protein and RNA (ribonucleic acid).
In eukaryotes the ribosome is 80S and made of
a 60S large subunit + a 40S small subunit.
Eukaryotic chloroplasts and mitochondria
contain prokaryote-like 70S ribosomes.

51. Mitochondria
Site of cellular
respiration (Energy from the breakdown of
organic molecules isused to phosphorylate
ADP to produce ATP)
“powerhouse of the cell”
More metabolic activity= more
mitochondria

52. Chloroplast
Found in plants and eukaryotic algae
Site of photosynthesis
Contain the green pigment chlorophyll
ChloroplastStructure
Thylakoids
• Grana = stacks of thylakoids
• (Light Dependent Phase)
Stroma
• Fluid outside the thylakoids

53. Cytoskeleton
Maintains shape of cell
Responsible for movement of cell and
movement of organelles within cell
Made of three types of protein fibers:
Microtubules, microfilaments &
intermediate filaments
Components of Cytoskeleton:
Microtubules – 25 nm diameter
Intermediate Filaments – 8 – 12 nm
diameter
Microfilaments – 7 nm diameter
Microtubules: Hollow tubes made up of A-
and B tubulin responsible for cell motility