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Questions and Answers
What is the primary function of free ribosomes in bacterial cells?
What is the primary function of free ribosomes in bacterial cells?
What type of genetic material do plasmids carry that can provide bacteria a selective advantage?
What type of genetic material do plasmids carry that can provide bacteria a selective advantage?
Which statement accurately describes the nucleoid in bacterial cells?
Which statement accurately describes the nucleoid in bacterial cells?
Which structure is primarily responsible for bacterial motility?
Which structure is primarily responsible for bacterial motility?
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What differentiates pili from fimbriae in bacterial cells?
What differentiates pili from fimbriae in bacterial cells?
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What is the primary component of the bacterial cell wall?
What is the primary component of the bacterial cell wall?
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Which shape describes 'bacilli' bacteria?
Which shape describes 'bacilli' bacteria?
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What is the function of the bacterial capsule?
What is the function of the bacterial capsule?
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How do gram-positive and gram-negative bacteria differ in terms of their cell wall structure?
How do gram-positive and gram-negative bacteria differ in terms of their cell wall structure?
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What role does the plasma membrane play in bacterial cells?
What role does the plasma membrane play in bacterial cells?
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Which of the following correctly describes ribosomes in bacterial cells?
Which of the following correctly describes ribosomes in bacterial cells?
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What is the term used to describe bacteria that can exhibit multiple forms?
What is the term used to describe bacteria that can exhibit multiple forms?
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Which process is NOT associated with the plasma membrane in bacterial cells?
Which process is NOT associated with the plasma membrane in bacterial cells?
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Study Notes
Bacteria: Structure and Function
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Bacteria are prokaryotic cells, lacking a nucleus and membrane-bound organelles (mitochondria, endoplasmic reticulum, Golgi).
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Cell Envelope: Surrounds bacterial cells; multi-layered.
Cell Wall
- Outermost layer; provides protection and shape.
- Primarily peptidoglycan, a unique mesh-like polymer.
- Gram-positive bacteria have a thick peptidoglycan layer, retaining Gram stain.
- Gram-negative bacteria have a thinner peptidoglycan layer, sandwiched between outer membrane and plasma membrane, not retaining Gram stain.
- Determines bacterial shape:
- Cocci: Round
- Bacilli: Rod-shaped
- Spirilla: Spiral
- Pleomorphic: Variable shapes.
Capsule
- Some bacteria have a capsule, an additional protective layer.
- Aids resistance to phagocytosis and adherence to surfaces.
- Crucial virulence factor; strains without a capsule are often less pathogenic.
Plasma Membrane
- Encloses cytoplasm; selectively permeable barrier.
- Regulates ion and molecule passage to maintain internal environment.
- Essential for:
- Respiration (energy production).
- Photosynthesis (light energy in photosynthetic bacteria).
- Lipid and cell wall component synthesis.
Cytoplasm
- Gel-like substance filling the cell; primarily water, contains:
- Cell components (ribosomes, nucleoid).
- Enzymes (catalysts).
- Organic molecules (nutrients, building blocks).
Ribosomes
- Site of protein synthesis.
- Free ribosomes (scattered in cytoplasm) produce proteins for cell use.
- Membrane-associated ribosomes synthesize proteins destined for the cell envelope or export.
Nucleoid
- Irregularly shaped region within cytoplasm, houses the chromosome.
- Most bacteria have a single circular chromosome, some linear, or multiple.
- Contains genes for essential functions (protein synthesis, etc.).
Plasmids
- Small, double-stranded DNA molecules (extrachromosomal).
- Replicate independently of the chromosome.
- Often carry beneficial genes, e.g., antibiotic resistance.
External Structures
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Pili (Fimbriae): Hair-like structures aid attachment to surfaces or other cells.
- Shorter pili (fimbriae) primarily for adherence.
- Flagella: Whip-like structures enable movement.
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Description
Test your knowledge on the structure and function of bacteria. This quiz covers essential topics such as the cell envelope, cell wall composition, and differences between Gram-positive and Gram-negative bacteria. Refresh your understanding of bacterial morphology and their unique characteristics.
