Chapter 3
Functional Anatomy of Prokaryotic
and Eukaryotic Cells

Prokaryotes can be grouped based on
morphology


Genetically determined
 Monomorphic vs pleomorphic
Size Range
 0.2 to 80 um in diameter
 2 to 600 um in length

Average size: 0.2 -1.0 µm × 2 - 8 µm
Morphology of Prokaryotic Cells

Prokaryotes exhibit a
variety of shapes

Most common

Spiral

Uncommon Shapes
Stella
Haloarcula

Cells may form groupings
Cells adhere together after division
 Form characteristic arrangements

 Depends
on plan of division
Neisseria
Enterococcus
Micrococcus
Sarcina
Staphylococcus aureus
Bacillus anthracis
Bacillus megaterium
Bordetella pertussis
Layers External to Cell Wall

Glycocalyx
 Made
inside the cell; excreted to surface
 General functions
 Protection
 Attachment
 Motility

Capsule or Slime Layer

Chemical composition varies
depending on species
Flagella


Naked filaments composed of flagellin
Rotate clockwise/counterclockwise
 Runs and tumbles
 Taxis

Flagella structure has
three basic parts

Filament

Hook

Basal body
Polar - Monotrichous
Polar -Lophotrichous
Peritrichous
Polar -amphitrichous
Axial filaments

Bundles of endoflagella that spiral around cell

Spirochete bacteria only

Corkscrew motion
Attachment Proteins

Fimbriae - bacteria



Hami – archaea



Filaments of pilin protein
Attachment
Hooked protein filament
Attachment
Sex Pili


Pilin tubules
Exchange of DNA
•
•
Cannulae – thermophilic archaea
Spinae - marine bacteria
•
•
Connect cells over distances
Creates mesh-like network
Prokaryotic Cell Wall
Determines shape of cell
 Protects from osmotic pressure
 Anchor point for flagella
 Contributes to virulence


Unique chemical structure
Bacteria vs. Archaea
 Gram positive vs. Gram-negative


Peptidoglycan (PTG) (murein)
Sugar found only in bacteria
 Archaea may have proteins or alternate sugars


Basic structure of PTG

Disaccharide polymer



N-acetylglucosamin (NAG)
N-acetylmuramic acid (NAM)
Glycan chain held together by
amino acids


Tetrapeptide chain
Protein crossbridges may or may
not be present

Mostly G+

Gram positive cell wall

Thick layer of PTG

Teichoic acids



Lipoteichoic or Wall
teichoic acids
Polyalcohols that provide
antigenic specificity
May have external
protein or sugar layer

Gram-negative cell wall

Little or no PTG

Outer lipopolysaccharide
membrane (LPS)



O-specific polysaccharide
side chain
Lipid A endotoxin
Significant periplasmic
space
GRAM STAINING

Gram-positive and gram-negative bacteria can be
identified using a “gram stain”
Summary of Gram + vs. Gram –

G+ cell





many rigid layers of peptidoglycan
teichoic acids
No outer LPS membrane
2 ring basal body anchoring flagella
G- cell




Little or no peptidoglycan
no teichoic acids
LPS outer membrane
4 ring basal body anchoring flagella
Atypical cell wall

Acid-fast cell walls




Classified as gram-positive
mycolic acid bound to PTG
Mycobacterium
Nocardia

Chlamydia


Classified as Gram – with
no PTG
cysteine-rich proteins

No cell wall
Mycoplasmas
 Sterols in plasma membrane

Structures Internal to Cell Wall

Cytoplasmic membrane
Delicate thin fluid structure
 Defines boundary
 Serves as a semi permeable barrier


Fluid mosaic model

Phospholipid Bilayer
 Amphipathic

Embedded with numerous proteins


receptors , transport, enzymes
Prokaryotes typicallydon’t have membrane sterols

Bacteria may have hopanoids

Photosynthetic pigments on in-foldings

chromatophores or thylakoids

Archaea have distinct membrane lipids

Ether linkage
 Diether
or tetraether
Glycerol group enantiomer
 Branched isoprenoid sidechain
 May form mono-layer with greater rigidity

Top: archaeal phospholipid, 1 isoprene sidechain, 2 ether linkage, 3 L-glycerol, 4 phosphate group
Middle:bacterial and eukaryotic phospholipid: 5 fatty acid, 6 ester linkage, 7 D-glycerol, 8 phosphate group
Bottom: 9 lipid bilayer of bacteria and eukaryotes, 10 lipid monolayer of some archaea.

Membrane is selectively permeable
Few molecules pass through freely
 Movement involves both active and passive
processes


passive processes
no energy (ATP) required
 Along gradient
 simple diffusion, facilitated diffusion, osmosis


Simple diffusion

Facilitated diffusion


Osmosis
Osmotic pressure
 active
processes
 energy
(ATP) required
 Active
transport

Group translocation

Phosphotransferase system

PEP group translocation
PEP transferase animation
Internal Structures

Structures essential for life



Chromosome
Ribosome
Optional but may provide selective advantage




Cytoskeleton
Plasmid
Storage granules
Endospores
Internal Structures

Primary Chromosome





Resides in nucleoid
Typically single circular
chromosome
Archaea - histone proteins
Bacteria - condensin protiens
Asexual reproduction

Binary fission, budding, fragmenting,
spores

Plasmids
 Small
DNA molecules
 replicated independently
 nonessential information
 used in genetic engineering biotechnology

Ribosomes (70S)


Composed of large and small subunits
 made of riboprotein and ribosomal RNA
differ in density from eukaryotic ribosomes
• Inclusions







Metachromatic granules
Polysaccharide granules
lipid inclusions
sulfur granules
carboxyzomes
magnetosomes
Gas vesicles

Endospores

“Resting cells”

Highly resistant


Heat, desiccation,
chemicals and UV light
Not reproduction!
Endospore producers include
Clostridium and Bacillus