Microbiology Chapter 4

Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells

Overview of Prokaryotic and Eukaryotic Cells

• Prokaryote:

  • Greek origin: "prenucleus"

  • Characteristics:

    • One circular chromosome, not in a membrane

    • No histones

    • No organelles

    • Bacteria: peptidoglycan cell walls

    • Archaea: pseudomurein cell walls

    • Division by binary fission

• Eukaryote:

  • Greek origin: "true nucleus"

  • Characteristics:

    • Paired chromosomes in nuclear membrane

    • Histones

    • Organelles

    • Polysaccharide cell walls (when present)

    • Division by mitosis

Size, Shape, and Arrangement of Bacterial Cells

• Shapes:

  • Bacillus: rod-shaped

  • Coccus: spherical-shaped

  • Spiral: includes Vibrio, Spirillum, Spirochete

  • Star-shaped

  • Rectangular

• Arrangements:

  • Pairs: diplococci, diplobacilli

  • Clusters: staphylococci

  • Chains: streptococci, streptobacilli

  • Groups of four: tetrads

  • Cubelike groups of eight: sarcinae

  • Scientific name and shape: Bacillus (shape: bacillus)

Prokaryotic Cell Structures

• Glycocalyx:

  • External to the cell wall, viscous and gelatinous

  • Made of polysaccharide and/or polypeptide

  • Two types: Capsule (organized and attached), Slime layer (unorganized and loose)

  • Contributes to virulence: capsules prevent phagocytosis, helps form biofilms

• Flagella:

  • Filamentous appendages that propel bacteria

  • Composed of protein flagellin

  • Structure: filament, hook, basal body

  • Function: movement (taxis), rotation (“run” or “tumble”), flagella proteins are H antigens (e.g., E. coli O157
    )

• Fimbriae and Pili:

  • Fimbriae: hairlike appendages for attachment

  • Pili: involved in motility (gliding, twitching) and DNA transfer (conjugation)

• Cell Wall:

  • Prevents osmotic lysis, protects the cell membrane

  • Made of peptidoglycan (in bacteria), contributes to pathogenicity

• Plasma (Cytoplasmic) Membrane:

  • Phospholipid bilayer, proteins embedded

  • Functions: selective permeability, ATP production, chromatophores (photosynthetic pigments)

  • Processes: passive (diffusion, osmosis) and active transport (requires energy)

• Cytoplasm:

  • Substance inside the plasma membrane

  • 80% water, proteins, carbohydrates, lipids, ions

• Nucleoid:

  • Contains DNA, bacterial chromosome, plasmids (extrachromosomal elements)

• Ribosomes:

  • Sites of protein synthesis, composed of protein and rRNA, 70S (50S + 30S subunits)

• Inclusions:

  • Various types for storage (e.g., phosphate, energy reserves)

• Endospores:

  • Resting cells, produced when nutrients are depleted

  • Resistant to desiccation, heat, chemicals, radiation

  • Produced by Bacillus and Clostridium

Eukaryotic Cell Structures

• Flagella and Cilia:

  • Projections for locomotion or moving substances

  • Flagella: long, few in number; Cilia: short, numerous

  • Structure: microtubules arranged in a 9+2 pattern

• Plasma (Cytoplasmic) Membrane:

  • Similar to prokaryotic membranes but includes sterols and carbohydrates

  • Functions: selective permeability, endocytosis (phagocytosis, pinocytosis)

• Cytoplasm:

  • Inside plasma, outside nucleus, includes cytosol and cytoskeleton

• Ribosomes:

  • 80S (60S + 40S subunits), membrane-bound (ER) or free (cytoplasm)

  • 70S in chloroplasts and mitochondria

• Nucleus:

  • Contains DNA, surrounded by a double membrane (nuclear envelope)

  • DNA with histones forms chromatin, condenses into chromosomes during mitosis/meiosis

• Endoplasmic Reticulum (ER):

  • Rough ER: protein synthesis

  • Smooth ER: synthesizes membranes, fats, hormones

• Golgi Complex:

  • Modifies proteins, transports them via vesicles

• Organelles:

  • Lysosomes: digestive enzymes

  • Vacuoles: storage, maintain shape

  • Mitochondria: ATP production, double membrane with cristae and matrix

  • Chloroplasts: photosynthesis, contains thylakoids with chlorophyll

  • Peroxisomes: oxidize fatty acids

  • Centrosomes: protein fibers and centrioles, form mitotic spindle

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Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells

Overview of Prokaryotic and Eukaryotic Cells

Prokaryote:

• Greek origin: "prenucleus"

• Characteristics:

  • One circular chromosome, not in a membrane

  • No histones

  • No organelles

  • Bacteria: peptidoglycan cell walls

  • Archaea: pseudomurein cell walls

  • Division by binary fission

Eukaryote:

• Greek origin: "true nucleus"

• Characteristics:

  • Paired chromosomes in nuclear membrane

  • Histones

  • Organelles

  • Polysaccharide cell walls (when present)

  • Division by mitosis

Size, Shape, and Arrangement of Bacterial Cells

• Average size: 0.2 to 2.0 μm diameter × 2 to 8 μm length

• Shapes:

  • Bacillus: rod-shaped

  • Coccus: spherical-shaped

  • Spiral: includes Vibrio, Spirillum, Spirochete

  • Star-shaped

  • Rectangular

• Arrangements:

  • Pairs: diplococci, diplobacilli

  • Clusters: staphylococci

  • Chains: streptococci, streptobacilli

  • Groups of four: tetrads

  • Cubelike groups of eight: sarcinae

  • Scientific name and shape: Bacillus (shape: bacillus)

Prokaryotic Cell Structures

Glycocalyx:

• External to the cell wall, viscous and gelatinous

• Made of polysaccharide and/or polypeptide

• Two types:

  • Capsule: organized and attached

  • Slime layer: unorganized and loose

• Contributes to virulence: capsules prevent phagocytosis, helps form biofilms

Flagella:

• Filamentous appendages that propel bacteria

• Composed of protein flagellin

• Structure: filament, hook, basal body

• Function: movement (taxis), rotation (“run” or “tumble”), flagella proteins are H antigens (e.g., E. coli O157)

Fimbriae and Pili:

• Fimbriae: hairlike appendages for attachment

• Pili: involved in motility (gliding, twitching) and DNA transfer (conjugation)

Cell Wall:

• Prevents osmotic lysis, protects the cell membrane

• Made of peptidoglycan (in bacteria), contributes to pathogenicity

Plasma (Cytoplasmic) Membrane:

• Phospholipid bilayer, proteins embedded

• Functions: selective permeability, ATP production, chromatophores (photosynthetic pigments)

• Processes: passive (diffusion, osmosis) and active transport (requires energy)

Cytoplasm:

• Substance inside the plasma membrane

• 80% water, proteins, carbohydrates, lipids, ions

Nucleoid:

• Contains DNA, bacterial chromosome, plasmids (extrachromosomal elements)

Ribosomes:

• Sites of protein synthesis, composed of protein and rRNA, 70S (50S + 30S subunits)

Inclusions:

• Various types for storage (e.g., phosphate, energy reserves)

Endospores:

• Resting cells, produced when nutrients are depleted

• Resistant to desiccation, heat, chemicals, radiation

• Produced by Bacillus and Clostridium

Eukaryotic Cell Structures

Flagella and Cilia:

• Projections for locomotion or moving substances

• Flagella: long, few in number

• Cilia: short, numerous

• Structure: microtubules arranged in a 9+2 pattern

Plasma (Cytoplasmic) Membrane:

• Similar to prokaryotic membranes but includes sterols and carbohydrates

• Functions: selective permeability, endocytosis (phagocytosis, pinocytosis)

Cytoplasm:

• Inside plasma, outside nucleus, includes cytosol and cytoskeleton

Ribosomes:

• 80S (60S + 40S subunits), membrane-bound (ER) or free (cytoplasm)

• 70S in chloroplasts and mitochondria

Nucleus:

• Contains DNA, surrounded by a double membrane (nuclear envelope)

• DNA with histones forms chromatin, condenses into chromosomes during mitosis/meiosis

Endoplasmic Reticulum (ER):

• Rough ER: protein synthesis

• Smooth ER: synthesizes membranes, fats, hormones

Golgi Complex:

• Modifies proteins, transports them via vesicles

Organelles:

• Lysosomes: digestive enzymes

• Vacuoles: storage, maintain shape

• Mitochondria: ATP production, double membrane with cristae and matrix

• Chloroplasts: photosynthesis, contains thylakoids with chlorophyll

• Peroxisomes: oxidize fatty acids

• Centrosomes: protein fibers and centrioles, form mitotic spindle