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Research the topic: Composition characteristics of gram positive and gram-negative cell wall. I will add my class powerpoint about the topic , you can also research online . Than make PowerPoint presentation (you can add pictures ) ,make sure to add a reference page .Page minimum 6 plus reference page
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Chapter 4: Functional Anatomy of Prokaryotic and
Eukaryotic Cells
© 2016 Pearson Education, Inc.
Comparing Prokaryotic and Eukaryotic Cells: An
Overview
Learning Objective
4-1 Compare the cell structure of prokaryotes and
eukaryotes.
© 2016 Pearson Education, Inc.
Comparing Prokaryotic and Eukaryotic Cells: An
Overview
• Prokaryote comes from the Greek words for
prenucleus.
• Eukaryote comes from the Greek words for
true nucleus.
© 2016 Pearson Education, Inc.
Comparing Prokaryotic and Eukaryotic Cells: An
Overview
Prokaryote
• Structurally simpler and
smaller than eukaryotes
• One circular chromosome,
not in a membrane
• No histones
• Few if any organelles
• Bacteria: peptidoglycan
cell walls
• Archaea: pseudomurein
cell walls
• Divides by binary fission
• May have glycocalyx
© 2016 Pearson Education, Inc.
Eukaryote
• Structurally more complex
and larger than
prokaryotes
• Multiple, paired
chromosomes,
in nuclear membrane
• Histones
• Organelles
• Polysaccharide cell walls,
when present
• Divides by mitosis
• May have glycocalyx
Comparing Prokaryotic and Eukaryotic Cells: An
Overview
Prokaryote
• Bacteria
1. Vast majority of
prokaryotes
2. Thousands of species
• Archaea
© 2016 Pearson Education, Inc.
Eukaryote
• Plants
• Animals
• Fungi (yeast, mold)
• Algae
• Protozoa
Archaea
• Prokaryotes
• Like bacteria
• Some have cell walls
• Those with cell walls lack peptidoglycan
• Often found in extreme environments
• 3 groups:
1. Methanogens produce methane gas
2. Extreme halophiles live in extreme salty
conditions (e.g. Dead Sea, Great Salt Lake)
3. Extreme thermophiles live in hot sulfurous water
(e.g. Yellowstone National Park hot springs)
© 2016 Pearson Education, Inc.
Check Your Understanding
✓ What is the main feature that distinguishes
prokaryotes from eukaryotes?
4-1
No nucleus vs. nucleus
© 2016 Pearson Education, Inc.
Comparing Prokaryotic and Eukaryotic Cells:
similarities
• Both have nucleic acid
• Both have proteins
• Both have lipids
• Both have carbohydrates
• Metabolize food via chemical reactions
• Build proteins via chemical reactions
• Store energy via chemical reactions
© 2016 Pearson Education, Inc.
Comparing Prokaryotic and Eukaryotic Cells:
Differences
• Structural differences in cell walls and membranes
• Organelles or lack of
© 2016 Pearson Education, Inc.
Comparing Prokaryotic and Eukaryotic Cells:
Differences
© 2016 Pearson Education, Inc.
The Prokaryotic Cell
Learning Objective
4-2 Identify the three basic shapes of bacteria.
Bacillus (rod-shaped, plural bacilli, meaning little rods or
walking sticks)
Coccus (spherical, plural cocci, meaning berries)
Spiral
© 2016 Pearson Education, Inc.
The Size, Shape, and Arrangement of Bacterial
Cells
• Average size: 0.2 to 2.0 µm in diameter and from 2
to 8 µm in length
• Most bacteria are monomorphic (single shape)
• A few are pleomorphic (many shapes)
• Shape is hereditary but can be changed by
environmental pressure
© 2016 Pearson Education, Inc.
The Size, Shape, and Arrangement of Bacterial
Cells
• Bacillus (rod-shaped)
• Coccus (spherical)
• Spiral
• Vibrio
• Spirillum
• Spirochete
• Star-shaped
• Rectangular
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Spiral bacteria
• Never straight
• Have one or more
twists
• Vibrios- bacteria that
look like curved rods
• Spirilla- helical shape,
rigid bodies, corkscrewlike, move via flagella
• Spirochetes- helical
and flexible, move via
axial filaments
© 2016 Pearson Education, Inc.
Star-shaped and rectangular prokaryotes (e.g. genus
Stella)
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Rectangular prokaryotes (e.g. halophilic archaea,
genus Haloarcula)
© 2016 Pearson Education, Inc.
The Size, Shape, and Arrangement of Bacterial
Cells
• Pairs: diplococci, diplobacilli (division in 1 plane)
• Chains: streptococci, streptobacilli (division in 1
plane)
• Groups of four: tetrads (division in 2 planes)
• Cubelike groups of eight: sarcinae (division in 3
planes)
• Clusters: staphylococci (division in multiple
planes)
© 2016 Pearson Education, Inc.
Cocci
Plane of
division
Diplococci
Sarcinae
Streptococci
Tetrad
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Staphylococci
Bacillus has two meanings:
• Scientific name (genus): Bacillus
• Shape: bacillus
• Bacilli divide only across their short axis, so there
are fewer groupings than cocci
• Can look like straws, rods, rods with tapered ends,
cigars, oval-rod (e.g. coccobacilli)
© 2016 Pearson Education, Inc.
Bacilli
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Bacilli
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Gram-stained Bacillus anthracis.
© 2016 Pearson Education, Inc.
Check Your Understanding
✓ Why don’t bacilli form tetrads, sarcinae or
clusters?
Bacilli divide only across their short axis, so there are fewer
groupings than cocci
© 2016 Pearson Education, Inc.
Check Your Understanding
✓ How can you identify streptococci with a
microscope?
4-2
The Size, Shape, and Arrangement of Bacterial Cells
© 2016 Pearson Education, Inc.
Structures External to the Cell Wall
Learning Objectives
4-3 Describe the structure and function of the
glycocalyx.
4-4 Differentiate flagella, axial filaments, fimbriae,
and pili.
© 2016 Pearson Education, Inc.
Glycocalyx (means sugar coat)
• External to the cell wall, secreted
• Viscous and gelatinous polymer surrounding a cell
• Sticky carbohydrate layer
• Made of polysaccharide and/or polypeptide
• carbohydrates covalently bound to plasma membrane
proteins and lipids form glycolipids and glycoproteins
• glycolipids and glycoproteins anchor the glycocalyx to
the cell wall
• Two types (ID by negative staining)
• Capsule: neatly organized and firmly attached to cell wall
• Slime layer: unorganized and loosely attached to cell wall
© 2016 Pearson Education, Inc.
Glycocalyx
• Extracellular polymeric substance (EPS) – glycocalyx
that helps cells adhere to one another and to surfaces
in their environment
• Extracellular polymeric substance helps form
biofilms
• 99% of bacteria in nature exist in biofilms
• EPS functions- cell protection, cell-cell adhesion, cell
adhesion to environmental surfaces, cell-cell
recognition/communication, promotes biofilm
formation in bacteria
• Can adhere to teeth, rocks in fast moving streams,
plant roots, medical implants, heart valves, etc.
© 2016 Pearson Education, Inc.
Glycocalyx
• Contribute to virulence
• Virulence= the degree to which a pathogen causes
disease
• Capsules prevent phagocytosis
• Phagocytosis= cellular ingestion and digestion of
microbes and other solid particles
• Bacillus anthracis and streptococcus pneumonia have
capsules, cannot be phagocytosed and cause disease
only when encapsulated.
• Functions (in addition to EPS functions)= prevention of
dehydration, prevention of loss of nutrients out of the
cell via viscosity
© 2016 Pearson Education, Inc.
Streptococcus pneumoniae, the cause of
pneumococcal pneumonia.
Capsules
© 2016 Pearson Education, Inc.
Flagella
• Filamentous appendages external to the cell
• Propel bacteria, motility, locomotion
• Made of protein flagellin
• Bacteria lacking flagella are called atrichous
(meaning without projections)
© 2016 Pearson Education, Inc.
Flagella
• Three parts:
• Filament: long outermost region
• Hook: attaches to the filament
• Basal body: consists of a rod and pair(s) of
rings; anchors flagellum to the cell wall and
membrane
• Eukaryotic cell flagella and cilia are more
complex than prokaryotic cells
© 2016 Pearson Education, Inc.
The structure of a prokaryotic flagellum (gram-negative)
© 2016 Pearson Education, Inc.
The structure of a prokaryotic flagellum (gram-positive)
Flagellum
Filament
Grampositive
Cell wall
Hook
Basal body
Peptidoglycan
Plasma
membrane
Cytoplasm
© 2016 Pearson Education, Inc.
Parts and attachment of a flagellum of a
gram-positive bacterium
Flagella: Structure
PLAY
© 2016 Pearson Education, Inc.
Animation: Flagella: Structure
Arrangements of bacterial flagella
Flagella
distributed
over the
entire cell
© 2016 Pearson Education, Inc.
Single
flagellum at
one pole/end
of cell
Tuft of multiple Flagella at
both poles
flagellum at
of cell
one pole of
cell
Flagella: Arrangement
PLAY
© 2016 Pearson Education, Inc.
Animation: Flagella: Arrangement
Flagella
• Flagella allow bacteria to move toward or away
from stimuli (taxis)
• Flagella rotate clockwise or counter-clockwise to
“run/swim” or “tumble”
• Run/swim- bacterial motility in one direction for a
length of time
• Tumble- periodic, abrupt, random changes in
bacterial motility interrupting a run/swim
• Receptors communicate to flagella whether to run
towards an attractant or away from a repellant
© 2016 Pearson Education, Inc.
Motility
PLAY
© 2016 Pearson Education, Inc.
Animation: Motility
Figure 4.9a Flagella and bacterial motility.
© 2016 Pearson Education, Inc.
Flagella: Movement
PLAY
© 2016 Pearson Education, Inc.
Animation: Flagella: Movement
Flagella
• In contrast to whip-like rotation of prokaryotic
flagella, eukaryotic flagella undulate in a wave-like
motion
• Flagellar rotation depends on continuous
production of cellular energy
• Taxis- motility permits bacterium to move towards
a favorable environment and away from an
unfavorable one
• Chemotaxis- taxis in response to a chemical
gradient
• Phototaxis- taxis in response to a light gradient
© 2016 Pearson Education, Inc.
Flagella
• If bacterial motility is in response to an attractant
(positive stimulus) there are many runs/swims and
few tumbles
• If bacterial motility is in response to an repellant
(negative stimulus) the frequency of tumbles
increases as the bacteria move away
• Side note; flagellar proteins (e.g. E. coli H antigen)
can be used to distinguish between variations
within a species (serovars) of gram negative
bacteria
© 2016 Pearson Education, Inc.
Axial Filaments
• Also called endoflagella
• Axial filaments/endoflagella- bundles of fibrils that
arise at the ends of the cell beneath an outer
sheath and spiral around the cell
• Found in spirochetes
• Examples of spirochetes include Treponema
pallidium (causes syphilis) and Borrrelia
burgdorferi (causes Lyme disease)
• Anchored at one end of a cell
• Rotation causes movement of the outer sheath
that propels the cell to move like a corkscrew
moves through a cork (in a spiral motion)
© 2016 Pearson Education, Inc.
Axial filaments
Axial
filament
Cell wall
Outer sheath
A diagram of axial filaments wrapping around part
of a spirochete
© 2016 Pearson Education, Inc.
Axial filaments
Axial filament
A photomicrograph of the spirochete
Leptospira, showing an axial filament
© 2016 Pearson Education, Inc.
Spirochetes
PLAY
© 2016 Pearson Education, Inc.
Animation: Spirochetes
Fimbriae
• Fimbriae
• Found in gram negative bacteria
• Hairlike appendages that are shorter, straighter and
thinner than flagella
• Consist of pilin protein
• Occur at the poles of a cell or evenly distributed over the
entire surface of a cell
• Fimbriae allow for attachment to each other and to
surfaces (epithelial cells, rocks, glass, liquids)
• Involved in forming biofilms
• Neisseria gonorrhoeae and E. coli have fimbriae
© 2016 Pearson Education, Inc.
Figure 4.11 Fimbriae.
Fimbriae
© 2016 Pearson Education, Inc.
Pili
• Pili
• Found in gram negative bacteria
• Hairlike appendages that are shorter, straighter and
thinner than flagella, longer than fimbriae
• Consist of pilin protein
• Only 1 or 2 pili per cell
• Involved in motility (gliding and twitching motility)
• Conjugation pili involved in DNA transfer from one cell
to another
• Neisseria gonorrhoeae, Psuedomonas aeruginosa and
some strains of E. coli have pili
© 2016 Pearson Education, Inc.
Check Your Understanding
✓ Why are bacterial capsules medically important
They prevent bacteria from being phagocytosed
by host immune cells
✓ How do bacteria move?
Pili, flagella, axial filaments
✓ How do basal bodies from gram negative and
gram positive bacteria differ?
2 versus 1 pair of rings
✓ What is bacteria without flagella called?
atrichous
✓ How are endoflagella different from flagella?
internal versus external, etc.
© 2016 Pearson Education, Inc.
The Structure of a Prokaryotic Cell
Capsule
© 2016 Pearson Education, Inc.
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