This document discusses the structure of bacterial cells. It covers the key components of bacterial cells including the cell morphology, cell wall, plasma membrane, fimbriae and pili, glycocalyx, flagella, internal structures like DNA and ribosomes, intracellular membranes, and cytoskeleton. Each component is defined and its main functions are described in 1-2 sentences.

1. Affiliated to Dr. Babasaheb Ambedkar Technological University , Lonere, Raigad
Pesented by :-
Heena Mehta
Asst. Proffesor
* Shri Vidyarthi Sudhar Sangh
NAGPUR COLLEGE OF PHARMACY

2. * STRUCTURE OF BACTERIAL CELL :
1. CELL MORPHOLOGY .
2. CELL WALL.
3. PLASMA MEMBRANE.
4. FIMBRI AND PILLI.
5. GLYCOCALYX.
6. FLAGELLA.
7. INTERNAL STRUCTURE
8. THE BACTERIAL DNA AND PLASMIDS.
9. RIBOSOMES AND OTHER MULTIPROTEIN COMPLEXES.
10.THE INTRACELLULAR MEMBRANE.
11.CYTOSKELETON.
*CONTENT:

3. *STRUCTURE OF A BACTERIAL CELL : -

4. 1. Cell shape is generally characteristic of a given
bacteria species but can vary depending on growth
conditions .
2. The most elemental structural property of bacteria is
their morphology (shape) . Typically it includes –COCCUS
,BACILLUS, COCCOBACILLUS ,SPIRAL ,FILAMENTOUS .
3. The most obvious structural characteristics of bacteria
is their small sized for example – E coil cells an
average sized bacterium are about 2 micrometers long
and 0.5 micrometers in diameter with a cell volume
of 0.6-0.7 micrometers .
4. Small size is extremely important because it allows
for a large surface area to volume ratio which allows
for rapid uptake and intracellular distribution of
nutrients and excretion of wastes .
* CELL MORPHOLOGY

5. 1. The cell envelope is composed of the cell
membrane and the cell walls .
2. Bacterial cell wall provides structural integrity to
the cell .
3. In prokaryotes ,the primarily functions of cell wall
is to protect the cell from internal turgor pressure.
4. Peptidoglycan is made up of a polysaccharide
backbone consisting of alternating N- Acetylmuramic
acid (NAM ) and N –Acetylgluosamine (NAG ) residue
in equal amounts .
5. THE GRAM POSITIVE CELL WALL are thick and the
peptidoglycan layer constitutes almost 95 % of the
cell wall .It takes up the cystol violet dye and are
stained purple .
6. THE GEAM NEGATIVE CELL WALL are much thinner
than the gram positive cell wall and they contain
a second plasma membrane .They are stained as
pink color .
* CELL WALL : -

6. 1. The plasma membrane or bacterial cytoplasmic
membrane is composed of a phospholipid bilayer .Thus,
has all of the general functions of a cell membrane .
2. As a phospholipid bilayer, the lipid protein of the
bacterial outer membrane is impermeable to charged
molecules .
3. The periplasm contains the peptidoglycan layer and
many proteins responsible for substrate binding or
hydrolysis and reception of extracellular signals .
4. Because of its location between the cytoplasmic and
outer membrane ,signals received and substrates bound
are available to be transported across the cytoplasmic
membrane using transport and signalling proteins
imbedded there .
* PLASMA MEMBRANE : -

7. 1. Fimbriae are protein tubes that extends out from the
outer membrane in many members of the proteobacteria
2. They are generally short in length and present in high
number about the entire bacterial cell surface .
3. Fimbriae usually function to facilitate the attachments
of a bacterial to a surface or to the other cells .
4. A few organisms use fimbriae for motility to facilitate
the assembly of multicellular structure such as fruiting
bodies .
5. Pilli are similar in structure to fimbriae but are much
longer and present on the bacterial cell in low
member
6. Pilli are involved in the process of bacterial
conjugation where they are called conjugated pilli as
“sex pilli “ also aid bacteria in gripping surfaces .
* FIMBRIAE AND PILLI :-

8. 1. Many bacteria secrete extracellular
polymers outside of their cell walls called
glycocalyx .
2. Capsules are relatively impermeable
structure that cannot be stained with dyes
such as INDIA ink .
3. The structures help in protecting bacteria
from phagocytosis and desiccation .
4. Slime layer is involved in attachment of
bacteria to outer cells or inanimate surface
to form biofilms .
* GLYCOCALYX : -

9. 1. Flagella are whip –like structure protecting from
bacterial cell wall and are responsible for
bacterial motility .
2. The arrangement of flagella about the bacterial
cell is unique to the species observed .
3. Common forms include :- MONOTRICHOUS - single
flagellum ,LOPHOTRICHOUS – a tuyt of flagella
found at one of the cell poles , AMPHITRICHOUS
–single flagellum found at each of two opposite
poles ,PERITRICHOUS – multiple flagella found at
several locations about the cell .
*FLAGELLA :-

10.  In comparison to eukaryotic , the intracellular
features of the bacterial cell are extremely
simple.
 Bacteria do not contain organelles in the same
sense of eukaryotes.
 Instead, the chromosomes and perhaps the
ribosomes are the most easily observable
intracellular structure found in all bacteria .
 There do exist , however, specialized group of
bacteria that contain more complex intracellular
structure .
*INTERNAL STRUCTURE

11.  Bacterial DNA can be located in :
I. Bacterial chromosomes : located in the irregular shaped
region as the nucleoid
II. Extrachromosomal DNA : located outside of the nucleoid
region as circular or linear plasmids .
 The bacterial DNA is not packaged using histones from
chromatin as in eukaryotes but instead exists as a highly
compact supercoiled structure.
 Plasmids can be easily gained or lost by a bacterium and can
be transferred between bacteria as a form of horizontal gene
transfer .
* THE BACTERIAL DNA AND
PLASMIDS

12. 1. In most bacteria the most numerous intracellular
structure is the ribosomes , the site of protein
synthesis in all living organisms
2. All prokaryote have 70S ribosomes while
eukaryotes have 80 S ribosomes in their cytosol.
3. The rRNA molecules differ in size in eukaryotes and
are complexed with a large number of ribosomal
protein .
4. The Ribosome is the most commonly observed
intracellular multiprotein complex in bacteria
other large complexes do occur and can sometimes
be seen using microscopy.
* RIBOSOMES AND OTHER
MULTIPROTEIN COMPLEXES

13.  Chromatophores are intracellular membrane
found in phototropic bacteria .
 An early idea was that bacteria might contain
membrane folds termed mesosomes .
 But , these were later shown to be artifacts
produced by the chemical used to prepare the
cell for electron microscope .
 Examples of bacteria containing intracellular
membrane are phototrophs , nitrifying bacteria
and methane oxidising bacteria .
* THE INTRACELLULAR MEMBRANE

14.  Cytoskeleton is a complex, dynamic
network of interlinking protein filament
present in the cytoplasm of the cell.
 Homologues for all major cytoskeleton
proteins in eukaryotes have been found in
prokaryotes .
 The prokaryotic cytoskeleton is the
collective name for all structure filaments
in prokaryotes .
 Cytoskeletal element plays essential roles
in cell division , protection , shape
determination , and polarity determination
in various prokaryotes .
*CYTOSKELETON

15. *