Prokaryotic cells lack a nucleus and membrane-bound organelles. They have a cell wall composed of peptidoglycan and a plasma membrane. Gram-positive bacteria have a thick cell wall primarily of peptidoglycan, while Gram-negative bacteria have a thin cell wall surrounded by an outer membrane containing lipopolysaccharides and lipoproteins. Prokaryotes reproduce asexually through binary fission and can also exchange genetic material through transformation, transduction, and conjugation. The plasma membrane is selectively permeable and surrounds the prokaryotic cell.

1. CHARACTERISTICS OF PROKARYOTIC CELL
 They lack a nuclear membrane.
 Mitochondria, Golgi bodies, chloroplast, and
lysosomes are absent.
 The genetic material is present on a single
chromosome.
 The histone proteins, the important
constituents of eukaryotic chromosomes, are
lacking in them.
 The cell wall is made up of carbohydrates and
amino acids.
 The plasma membrane acts as the
mitochondrial membrane carrying respiratory
enzymes.
 They divide asexually by binary fission. The
sexual mode of reproduction involves
conjugation.
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2. DEFINITION
 A prokaryotic cell is a type of cell that does not have
a true nucleus or membrane-bound organelles.
Organisms within the domains Bacteria and
Archaea are based on the prokaryotic cell, while all
other forms of life are eukaryotic. However,
organisms with prokaryotic cells are very abundant
and make up much of Earth’s biomass.
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3. PROKARYOTIC CELL STRUCTURE
 A prokaryotic cell does not have a nuclear
membrane. However, the genetic material is
present in a region in the cytoplasm known as the
nucleoid. They may be spherical, rod-shaped, or
spiral.
 Capsule– It is an outer protective covering found in
the bacterial cells, in addition to the cell wall. It
helps in moisture retention, protects the cell when
engulfed, and helps in the attachment of cells to
nutrients and surfaces.
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4. PROKARYOTIC CELL STRUCTURE CONT..
 Cell Wall– It is the outermost layer of the cell which
gives shape to the cell.
 Cytoplasm– The cytoplasm is mainly composed of
enzymes, salts, cell organelles and is a gel-like
component.
 Cell Membrane– This layer surrounds the
cytoplasm and regulates the entry and exit of
substances in the cells.
 Pili– These are hair-like outgrowths that attach to
the surface of other bacterial cells.
 Flagella– These are long structures in the form of a
whip, that help in the locomotion of a cell.
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5. PROKARYOTIC CELL STRUCTURE CONT
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6.  Ribosomes: Ribosomes are cell structures
responsible for protein production.
 Plasmids: Plasmids are gene-carrying, circular
DNA structures that are not involved in
reproduction.
 Nucleoid Region: Area of the cytoplasm that
contains the single bacterial DNA molecule.
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7. REFERENCE
 Bailey, Regina. "What Are Prokaryotic Cells?
Structure, Function, and Definition." ThoughtCo,
Apr. 5, 2023, thoughtco.com/prokaryotes-meaning-
373369.
 Biologydictionary.net Editors. "Prokaryotic
Cell." Biology Dictionary, Biologydictionary.net, 18
Dec. 2016, https://biologydictionary.net/prokaryotic-
cell/
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8. HOW DO PROKARYOTIC CELLS DIVIDE?
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9.  Prokaryotic cells divide through the process of binary
fission. Unlike mitosis, this process does not involve
the condensation of DNA or the duplication of
organelles. Prokaryotic cells have only a small amount
of DNA, which is not stored in complex chromosomes.
Further, there are no organelles so there is nothing to
divide.
 When a prokaryote grows to a large size, the process of
binary fission takes place. This process duplicates the
DNA, then separates each new strand of DNA into
individual cells. This process is simpler than mitosis.
This means that bacteria can reproduce much faster
than most eukaryotic organisms.

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10. THE CELL WALL
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11. THE CELL WALL
 The cytoplasm of prokaryotic cells has a high
concentration of dissolved solutes. Therefore, the
osmotic pressure within the cell is relatively high.
 The cell wall is a protective layer that surrounds
some cells and gives them shape and rigidity.
 It is located outside the cell membrane and
prevents osmotic lysis (bursting due to increasing
volume).
 The chemical composition of the cell walls varies
between archaea and bacteria, and also varies
between bacterial species.
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12.  Bacterial cell walls contain peptidoglycan,
composed of polysaccharide chains that are cross-
linked by unusual peptides containing both L- and
D-amino acids including D-glutamic acid and D-
alanine.
 Proteins normally have only L-amino acids; as a
consequence, many of our antibiotics work by
mimicking D-amino acids and therefore have
specific effects on bacterial cell wall development.
 There are more than 100 different forms of
peptidoglycan. S-layer (surface layer) proteins are
also present on the outside of cell walls of both
archaea and bacteria.
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13.  The different bacterial responses to the staining
procedure are ultimately due to cell wall structure.
 Gram-positive organisms typically lack the outer
membrane found in Gram-negative organisms.
 Up to 90 percent of the cell wall in Gram-positive
bacteria is composed of peptidoglycan, and most of
the rest is composed of acidic substances
called teichoic acids.
 Teichoic acids may be covalently linked to lipids in
the plasma membrane to form lipoteichoic acids.
Lipoteichoic acids anchor the cell wall to the cell
membrane.
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14.  Gram-negative bacteria have a relatively thin cell
wall composed of a few layers of peptidoglycan
(only 10 percent of the total cell wall), surrounded
by an outer envelope containing
lipopolysaccharides (LPS) and lipoproteins.
 This outer envelope is sometimes referred to as a
second lipid bilayer. The chemistry of this outer
envelope is very different, however, from that of the
typical lipid bilayer that forms plasma membranes.
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 Bacteria are divided into two major groups: Gram positive and
Gram negative. Both groups have a cell wall composed of
peptidoglycan: in Gram-positive bacteria, the wall is thick,
whereas in Gram-negative bacteria, the wall is thin. In Gram-
negative bacteria, the cell wall is surrounded by an outer
membrane that contains lipopolysaccharides and lipoproteins.
Porins are proteins in this cell membrane that allow
substances to pass through the outer membrane of Gram-
negative bacteria. In Gram-positive bacteria, lipoteichoic acid
anchors the cell wall to the cell membrane.

16. Table 3.5.13.5.1: Structural Differences and Similarities between
Bacteria and Archaea
Structural
Characteristic
Bacteria Archaea
Cell type Prokaryotic Prokaryotic
Cell morphology Variable Variable
Cell wall
Contains
peptidoglycan
Does not contain
peptidoglycan
Cell membrane type Lipid bilayer
Lipid bilayer or lipid
monolayer
Plasma membrane
lipids
Fatty acids Phytanyl groups
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17. REPRODUCTION
 Reproduction in prokaryotes is asexual and usually
takes place by binary fission.
 Recall that the DNA of a prokaryote exists as a
single, circular chromosome. Prokaryotes do not
undergo mitosis.
 Rather the chromosome is replicated and the two
resulting copies separate from one another, due to
the growth of the cell.
 The prokaryote, now enlarged, is pinched inward at
its equator and the two resulting cells, which are
clones, separate.
 Binary fission does not provide an opportunity for
genetic recombination or genetic diversity, but
prokaryotes can share genes by three other
mechanisms.
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18. REPRODUCTION CONT..
 In transformation, the prokaryote takes in DNA found in its
environment that is shed by other prokaryotes. If a
nonpathogenic bacterium takes up DNA for a toxin gene from
a pathogen and incorporates the new DNA into its own
chromosome, it too may become pathogenic. In transduction,
bacteriophages, the viruses that infect bacteria, sometimes
also move short pieces of chromosomal DNA from one
bacterium to another.
 Transduction results in a recombinant organism.
 Archaea are not affected by bacteriophages but instead have
their own viruses that translocate genetic material from one
individual to another.
 In conjugation, DNA is transferred from one prokaryote to
another by means of a pilus, which brings the organisms into
contact with one another.
 The DNA transferred can be in the form of a plasmid or as a
hybrid, containing both plasmid and chromosomal DNA.
These three processes of DNA exchange
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19. REPRODUCTION CONT..
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20. REPRODUCTION CONT..
 Besides binary fission, there are three other
mechanisms by which prokaryotes can exchange DNA.
 In transformation, the cell takes up prokaryotic DNA
directly from the environment. The DNA may remain
separate as plasmid DNA or be incorporated into the
host genome.
 In transduction, a bacteriophage injects DNA into the
cell that contains a small fragment of DNA from a
different prokaryote.
 In conjugation, DNA is transferred from one cell to
another via a mating bridge that connects the two cells
after the sex pilus draws the two bacteria close enough
to form the bridge.
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21. THE PLASMA MEMBRANE
 The plasma membrane is a thin lipid bilayer (6 to 8
nanometers) that completely surrounds the cell and
separates the inside from the outside.
 Its selectively permeable nature keeps ions, proteins,
and other molecules within the cell and prevents them
from diffusing into the extracellular environment, while
other molecules may move through the membrane.
 Recall that the general structure of a cell membrane is a
phospholipid bilayer composed of two layers of lipid
molecules. In archaeal cell membranes, isoprene
(phytanyl) chains linked to glycerol replace the fatty
acids linked to glycerol in bacterial membranes.
 Some archaeal membranes are lipid monolayers instead
of bilayers
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22. THE PLASMA MEMBRAN
ARCHAEAL PHOSPHOLIPIDS DIFFER
FROM THOSE FOUND IN BACTERIA AND
EUKARYA IN TWO WAYS.
FIRST, THEY HAVE BRANCHED
PHYTANYL SIDECHAINS INSTEAD OF
LINEAR ONES. SECOND, AN ETHER
BOND INSTEAD OF AN ESTER BOND
CONNECTS THE LIPID TO THE
GLYCEROL.
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