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Questions and Answers
What is the main component of the cell wall in Gram-negative bacteria?
What is the main component of the cell wall in Gram-negative bacteria?
Which of the following correctly describes functions of the cytoplasmic membrane in bacteria?
Which of the following correctly describes functions of the cytoplasmic membrane in bacteria?
Which of these structures in bacteria serves as an external attachment mechanism?
Which of these structures in bacteria serves as an external attachment mechanism?
What is the purpose of the bacterial glycocalyx?
What is the purpose of the bacterial glycocalyx?
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In a typical bacterium, which component is NOT part of the cytoplasmic region?
In a typical bacterium, which component is NOT part of the cytoplasmic region?
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Which type of cellular arrangement is characterized by pairs of cocci?
Which type of cellular arrangement is characterized by pairs of cocci?
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What defines a spirochete amongst spiral bacteria?
What defines a spirochete amongst spiral bacteria?
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Which arrangement results from bacteria dividing along multiple random planes?
Which arrangement results from bacteria dividing along multiple random planes?
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What is the primary function of the outer membrane in Gram-negative bacteria?
What is the primary function of the outer membrane in Gram-negative bacteria?
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Which of the following is a characteristic feature of Gram-positive bacteria?
Which of the following is a characteristic feature of Gram-positive bacteria?
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What role does the bacterial glycocalyx play in bacterial virulence?
What role does the bacterial glycocalyx play in bacterial virulence?
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What is primarily found in the periplasmic space of Gram-negative bacteria?
What is primarily found in the periplasmic space of Gram-negative bacteria?
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Which structure is responsible for the segregation of DNA during binary fission in bacteria?
Which structure is responsible for the segregation of DNA during binary fission in bacteria?
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Which of the following best describes the composition of capsules in bacteria?
Which of the following best describes the composition of capsules in bacteria?
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What type of DNA do plasmids represent in bacterial cells?
What type of DNA do plasmids represent in bacterial cells?
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How do capsules assist bacteria in establishing infections?
How do capsules assist bacteria in establishing infections?
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What is the primary function of the peptidoglycan layer in bacterial cell walls?
What is the primary function of the peptidoglycan layer in bacterial cell walls?
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Which of the following is a characteristic of Gram-negative bacteria?
Which of the following is a characteristic of Gram-negative bacteria?
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Which component primarily distinguishes Gram-positive from Gram-negative bacteria?
Which component primarily distinguishes Gram-positive from Gram-negative bacteria?
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What role do common pili (fimbriae) play in bacterial attachment?
What role do common pili (fimbriae) play in bacterial attachment?
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What is the main structural component of the bacterial cell wall?
What is the main structural component of the bacterial cell wall?
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During conjugation, what is the function of the sex pilus?
During conjugation, what is the function of the sex pilus?
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Which part of the Gram-negative cell wall is responsible for the protein transport system?
Which part of the Gram-negative cell wall is responsible for the protein transport system?
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What is the primary role of teichoic acids in Gram-positive bacteria?
What is the primary role of teichoic acids in Gram-positive bacteria?
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What does the glycocalyx primarily assist bacteria with?
What does the glycocalyx primarily assist bacteria with?
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Which chemical structure provides rigidity to the bacterial cell wall?
Which chemical structure provides rigidity to the bacterial cell wall?
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Study Notes
Prokaryotic vs Eukaryotic Cells
- Prokaryotic cells lack a nucleus and other membrane-bound organelles.
- Eukaryotic cells have a nucleus and other membrane-bound organelles.
Prokaryotic Cell Structure
- Appendages: Flagella (for movement), pili (for attachment and conjugation).
- Cell Envelope: Capsule (protection and attachment), cell wall (strength and shape), plasma membrane (controls what enters and leaves the cell).
- Cytoplasmic Region: Chromosome (genetic material), ribosomes (protein synthesis), plasmids (small, extra-chromosomal DNA circles), inclusions (storage granules), and gas vesicles.
Eukaryotic Cell Structure
- Nucleus: Contains the cell's genetic material (DNA) organized into chromosomes.
- Organelles: Specialized structures with specific functions such as mitochondria, endoplasmic reticulum, Golgi apparatus, vacuoles, and lysosomes.
- Cell membrane: Acts as a barrier to the entry and exit of substances into and out of the cell.
- Cell wall: Present in some eukaryotic cells like plant and algal cells making them rigid and provides the cell with strength and structure, helping to retain shape.
- Cytoplasm: Contains all cell components found between the cell membrane and the nucleus where organelles, cytoskeleton, cytosol and inclusions (storage granules) are located.
Bacterial Morphology
- Cocci (cocci): Spherical-shaped bacteria.
- Bacilli (bacilli): Rod-shaped bacteria.
- Spirilla: Spiral-shaped bacteria.
- Vibrio: Curved, comma-shaped bacteria.
- Coccobacilli :Short round bacteria
- Pleomorphic bacteria: bacteria that can change shape.
Bacterial Arrangements
- Diplococci: Pairs of cocci.
- Streptococci: Chains of cocci.
- Staphylococci: Clusters of cocci.
- Tetrads: Groups of four cocci.
- Sarcina: Cubical packets of eight cocci.
- Diplobacilli: Pairs of bacilli
- Streptobacilli: Chains of bacilli
- Coccobacilli: Short bacilli
Bacterial Cell Walls
- Gram-positive: Thick peptidoglycan layer, teichoic acids.
- Gram-negative: Thin peptidoglycan layer, outer membrane, lipopolysaccharides, periplasmic space.
Bacterial Cell Envelope
- The outer covering of a bacterial cell consisting of capsule, cell wall and plasma membrane.
- The cell wall is an essential structure. Peptidoglycan protects from osmotic rupture or lysis.
Bacterial Motility
- Flagella: Filamentous protein structures that enable movement by rotating like propellers.
- Types of flagella include: monotrichous, lophotrichous, amphitrichous, peritrichous.
- Pili and Fimbriae: Hair-like structures that help cells adhere to surfaces and in bacterial conjugation.
- Types of pili include: common pili, sex pilus or F-pilus.
Bacterial Internal Structures
- Chromosome: Circular DNA molecule containing genetic information.
- Plasmids: Smaller, circular DNA molecules separate from the chromosome and often carry genes for antibiotic resistance.
- Ribosome: Site of protein synthesis, composed of large 50S subunit and small 30S subunit which combine to form 70S ribosome.
- Inclusions/Granules: storage for nutrients.
- Gas vesicles: allow bacteria to float.
- Endospores: dormant structures resistant to harsh conditions.
Techniques to Demonstrate Bacterial Motility
- Flagellar stains.
- Motility medium test.
- Direct microscopic observation of living bacteria in wet mounts.
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