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Questions and Answers
Which component forms the primary structure of the bacterial cell wall?
What type of structures are flagella in bacteria classified as?
Which of the following describes the glycan strands in peptidoglycan?
What is the primary function of the bacterial cell envelope?
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Which of the following best describes inclusion bodies in bacteria?
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What is a primary characteristic of the cell wall of Gram-positive bacteria?
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Which component is found in the outer membrane of Gram-negative bacteria?
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What is the role of porins in the outer membrane of Gram-negative bacteria?
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Which of the following is a consequence of cell death in Gram-negative bacteria?
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What structural feature differentiates the cell wall of Gram-negative from Gram-positive bacteria?
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What is the function of the strong negative charge of the outer membrane in Gram-negative bacteria?
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What does the term 'endotoxic shock' refer to?
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What component anchors the inner half of the outer membrane to the peptidoglycan layer in Gram-negative bacteria?
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What is a significant structural feature of Gram-negative bacteria compared to Gram-positive bacteria?
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Which component is found in the cell wall of Gram-negative bacteria but not in Gram-positive bacteria?
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How does the cell wall structure of Gram-negative bacteria contribute to their antibiotic resistance?
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Which of the following components is NOT present in the cell envelope of Gram-negative bacteria?
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What role do lipopolysaccharides (LPS) play in the cell wall of Gram-negative bacteria?
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What is the primary function of fimbriae in prokaryotic cells?
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What distinguishes pili from fimbriae in terms of structure and number?
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Which type of motility is associated with the function of pili in prokaryotic cells?
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Which protein is primarily responsible for the structure of pili?
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What roles do fimbriae play in biofilm formation?
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In prokaryotic cells, how are sex pili particularly important?
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Which statement about fimbriae is NOT true?
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How do fimbriae contribute to the colonization of host cells?
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What role do the peptide cross-bridges play in the structure of peptidoglycan?
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Which of the following is true about the tetrapeptide side chains in peptidoglycan?
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What is a primary function of the bacterial cell wall?
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What can occur in bacteria that lack a cell wall when placed in a hypotonic environment?
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Which amino sugars are the primary components of the carbohydrate backbone in peptidoglycan?
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How does the chemical composition of the cell wall assist in clinical settings?
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What protects bacteria from bursting due to osmotic pressure?
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What type of environment do bacteria typically thrive in regarding osmotic pressure?
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Study Notes
Bacterial Cell Structure
-
Peptidoglycan: A complex, semi-rigid layer outside the plasma membrane, essential for bacterial cell shape and integrity.
- Composed of glycan strands cross-linked by peptides.
- Glycan strands: Alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) linked by glycosidic bonds.
- Tetrapeptide side chains: Four amino acids attached to NAM in the glycan backbone.
- Peptide cross-bridges: Short chains of amino acids linking tetrapeptide side chains.
Bacterial Cell Envelope
-
Gram-positive bacteria: Possess a thick peptidoglycan layer.
- Teichoic acids: Embedded in peptidoglycan layer, contributing to the cell's negative charge.
- More susceptible to antibiotics that target peptidoglycan synthesis.
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Gram-negative bacteria: Have a thinner peptidoglycan layer and an additional outer membrane.
-
Outer membrane: Contains lipopolysaccharide (LPS) and porins.
- LPS: An endotoxin released upon cell death, causing fever and shock.
- Porins: Proteins forming channels for small molecules to cross the outer membrane.
- Periplasmic space: Located between the inner and outer membranes.
- Less susceptible to certain antibiotics due to the outer membrane barrier.
-
Outer membrane: Contains lipopolysaccharide (LPS) and porins.
External Structures
- Flagella: Long filamentous structures responsible for motility.
- Axial filaments: Found in spirochetes, providing corkscrew-like motility.
- Fimbriae: Short, hair-like appendages involved in adhesion to surfaces and host cells.
- Pili: Longer than fimbriae, involved in conjugation (DNA transfer) and twitching motility.
Comparison of Gram-positive and Gram-negative Bacteria
| Character | Gram-positive | Gram-negative |
|---|---|---|
| Overall thickness | Thick peptidoglycan layer | Thin peptidoglycan layer |
| Peptidoglycan | Present | Present |
| Teichoic acid | Present | Absent |
| Lipopolysaccharide | Absent | Present |
| Outer membrane | Absent | Present |
| Permeability to molecules | Less selective | More selective |
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Description
Explore the intricate details of bacterial cell structure, focusing on peptidoglycan and the differences between Gram-positive and Gram-negative bacteria. This quiz covers essential components such as glycan strands, tetrapeptide side chains, and the implications of cell envelope structure on antibiotic susceptibility.
