Download The Structure of a Prokaryotic Cell

Prokaryotic Structure and Function
What characteristics are useful
when classifying bacteria?
1. Bacterial shape (morphology)
2. Arrangement
3. Structural features
–
–
–
Cell wall biochemistry
Motility
Spore formation
Prokaryotic Cell Shapes (Morphologies)
rod shape
round shape
Branching Filaments
spiral shape
curved rod
Cell Shape (Morphology)
Other Terms Describing Morphology
• Monomorphic
– Having a single morphology
• Pleomorphic
– Having many morphologies
Streptomyces (soil bacteria)
Cell Arrangement (Cocci)
Match the following:
• Tetrad
• Staphylococci
• Micrococci
• Diplococci
• Streptococci
Cell Arrangement (Bacillus/Rod)
Single bacillus
Diplobacilli
Coccobacillus
Streptobacilli
The Structure of a Prokaryotic Cell
Endospore
Glycocalyx (sugar coat)
• a sticky, gel-like layer surrounding the cell
• made of polysaccharide, polypeptide, or both
• Two types:
1. slime layer - loosely organized and attached
2. capsule - highly organized, tightly attached
• Functions:
Glycocalyx / Capsule
What components comprise the cell wall?
• Function:
– Rigid structure
– Provides support
for the cell
• Structure:
– Composed of peptidoglycan
– Peptido• Contains amino acids
• Cross-bridges form between sugar
chains
– Glycan - sugars
• N-acetyl-glucosamine (NAG)
• N-acetyl-muramic acid (NAM)
What is the basis
for the gram stain?
What major structural component is
found in bacterial cell walls?
• Not in Archaebacteria
• Peptidoglycan
– Disaccharide polymer:
• N-acetylglucosamine
(NAG)
• N-acetylmuramic acid
(NAM)
– Bridged by amino
acids
Figure 4.12
Peptidoglycan Structure
Figure 4.13a
Gram-Positive Bacterial Cell Wall
Figure 4.13b
Gram-Negative Bacterial Cell Wall
Figure 4.13c
Gram-Positive vs. Gram-Negative
Gram-Positive
Gram Reaction Color
Peptidoglycan Layer
Teichoic Acids
Periplasm
Outer Membrane (OM)
Gram-Negative
Gram-Positive vs. Gram-Negative
Gram-Positive
Gram-Negative
Gram Reaction Color
Purple/Violet
Pink
Peptidoglycan Layer
Thick
Thin
Teichoic Acids
Yes
No
Periplasm
No
Yes
Outer Membrane (OM)
No
Yes
Gram-Positive vs. Gram-Negative
Gram-Positive
Endotoxin (LPS)
Penicillin
Susceptibility
Lysozyme
Susceptibility
Example
Organisms:
Gram-Negative
Gram-Positive vs. Gram-Negative
Gram-Positive
Gram-Negative
Endotoxin (LPS)
No
Yes
Penicillin
Susceptibility
Yes
No
Lysozyme
Susceptibility
Yes
No
Staphylococcus sp.
Streptococcus sp.
E. Coli
Salmonella sp.
Shigella sp.
Example
Organisms:
Atypical Cell Walls
• Acid-fast cell walls
– Mycobacterium and Nocardia
– Gram-positive cell wall structure with lipid: 60% mycolic
acid
– Resistant to chemicals
– Waxy, sticky
– Resists dehydration, long lived
• Mycoplasma
– Causes “walking pneumonia”
– No cell walls
- Cell membranes contain sterols
- Pleomorphic
The Plasma Membrane
Figure 4.14b
Plasma Membrane
• Composed of:
– Phospholipid bilayer
– Proteins: “float in Sea
of Phospholipids”
• Functions:
– Selective permeability
– Senses environmental
signals
– Energy transformation
– Porins allow access to
inner cytoplasmic
membrane
Movement Across Cell Membranes
• Simple Diffusion
– Movement from high conc. --> low conc.
• Facilitated Diffusion
– Movement via a carrier protein
• Active Transport
– Movement via carrier protein
– Requires energy
Movement Across Cell Membranes
Nonspecific
transporter
Transported
substance
Specific
transporter
Glucose
Osmosis
• Osmosis:
Cytoplasm Solute
Water
Plasma
membrane
How do bacteria get around?
Flagella
• Long, filamentous structures
• Function: Used for locomotion
• Structure: Composed of protein - flagellin
Arrangements of Bacterial Flagella
Figure 4.7
Bacteria
Motility
Periplasmic Flagella
• Found in spirochetes
• Located in
periplasmic space
Fimbriae
 Fine,
proteinaceous,
hairlike bristles
from the cell
surface
 Not for locomotion
 Adhesion
(surfaces, cells)
Figure 4.11
Pili
 Conjugative pilus
 Rigid tubular structure made of pilin protein
 Conjugation pili / sex pili:used for conjugation
(DNA transfer)
 Motility pili
 Gliding motility
 Twitching motility
Cytoplasm
• Primarily water (80%)
• Contains:
– Proteins (enzymes) and other macromolecules
– Small molecules and ions
– Ribosomes
Figure 4.6
What structures do all prokaryotes
share?
• Create a list:
What structures do all prokaryotes
share?
•
•
•
•
•
•
Cell membrane
Cytoplasm
Ribosomes
Cytoskeleton
DNA
Most have a:
– Cell wall
– Glycocalyx
How do bacteria store genetic
information?
Genetic Information – Bacterial
Chromosome
• Location: nucleoid region
within the cytoplasm (no
nucleus)
• Function: contains ‘blueprint’
for cell’s proteins
• Structure:
– Double stranded DNA
– Bacteria have a single, circular
chromosome
Genetic Information - Plasmids
• Function: Extra genetic information
• Structure: Composed of DNA
– Are small, circular “mini-chromosomes”
– NOTE: Plasmids can be transferred between bacteria!
Bacterial Ribosome
• Function:
• Structure:
Endospores
• Gram +
– Two major genera:
• Function:
– Survival of adverse conditions
– Is a “resting state”
• Sporulation = spore formation
• Germination = spore  vegetative cell
• 1 bacterium makes 1 spore, not a form of
replication
• Video:
– http://highered.mheducation.com/sites/0072552980/stud
ent_view0/chapter4/animation_quiz_.html
Figure 4.21a Formation of endospores by sporulation.
Cell wall
Cytoplasm
Spore septum begins to isolate
newly replicated DNA and a
small portion of cytoplasm.
Plasma membrane starts to
surround DNA, cytoplasm, and
membrane isolated in step 1.
Plasma
membrane
Bacterial
chromosome
(DNA)
Sporulation, the process of endospore
formation
Spore septum surrounds isolated portion,
forming forespore.
Two
membranes
Peptidoglycan
layer forms between membranes.
Endospore is freed
from cell.
Spore coat forms.
Medically Relevant Spore-forming Bacteria
• Bacillus anthracis
– Anthrax
• Clostridium tetani
– Tetanus
• Clostridium perfringens
– Gas gangrene
• Clostridium botulinum
– Botulism food poisoning
• Boiling not enough to
kill spores!!! Must use
pressurized steam at
120 C.
The Eukaryotic Cell
Figure 4.22a
Endosymbiotic Theory
Flagella and Cilia
Figure 4.23a-b
The Cell Wall and Glycocalyx
• Cell wall
– Plants, fungi
– Carbohydrates
• Cellulose, chitin, glucan, mannan
• Glycocalyx
– Carbohydrates extending from animal plasma
membrane
– Bonded to proteins and lipids in membrane
The Plasma Membrane
•
•
•
•
•
•
Phospholipid bilayer
Peripheral proteins
Integral proteins
Transmembrane proteins
Sterols
Glycocalyx carbohydrates
Cytoplasm
• Cytoplasm: Substance inside plasma
membrane and outside nucleus
• Cytosol: Fluid portion of cytoplasm
• Cytoskeleton: Microfilaments, intermediate
filaments, microtubules
Ribosomes
• 80S
• 70S
Organelles
• Nucleus: Contains chromosomes
• ER: Transport network
• Golgi complex: Membrane formation and
secretion
• Lysosome: Digestive enzymes
• Vacuole: Brings food into cells and provides
support
Organelles
• Mitochondrion: Cellular respiration
• Chloroplast: Photosynthesis
• Peroxisome: Oxidation of fatty acids; destroys
H2O2
The Eukaryotic Nucleus
Figure 4.24a–b
Endoplasmic Reticulum
• Endoplasmic Reticulum (ER)
• Connected to nuclear
membrane
• 2 Types:
– Rough ER
– Smooth ER
Golgi Complex
• Golgi apparatus
– Membrane formation, Protein modification &
packaging
– Forms temporary vesicles
Mitochondria
Figure 4.27
Prokaryotic
vs.
Eukaryotic
Prokaryotic Cell
Size:
Nucleus:
Membrane-Enclosed
Organelles
Ribosome size:
Examples:
Eukaryotic Cell
Prokaryotic
vs.
Eukaryotic
Prokaryotic Cell
Eukaryotic Cell
0.2 um - 2 um
10 um – 100 um
Nucleus:
No
Yes
Membrane-Enclosed
Organelles
No
Yes
70 S
80 S
S. aureus
B. Subtilis
M. luteus
Neuron
Muscle fiber
Paramecium
Size:
Ribosome size:
Examples: