Questions and Answers
What structures do all bacteria possess?
All bacterial cells have a cell membrane, cytoplasm, ribosomes, and one (or few) chromosomes; the majority have a cell wall and some form a surface coating or glycocalyx.
Name at least 4 structures that some, but not all bacteria possess.
Flagella, pili, fimbriae, S layer, cytoskeleton, inclusions, microcompartments, endospores, intracellular membranes.
Describe the 3 major shapes of bacteria.
Coccus: spherical or rod-shaped, Bacillus: cylindrical, Coccobacillus: elongated coccus; Vibrio: curved rod, Spirillum: rigid spiral, Spirochete: coiled spiral.
What are the structure and function of 6 different types of bacterial external structures?
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Explain how a flagellum works in the presence of an attractant.
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Why are gram-positive cell walls stronger than gram-negative cell walls?
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Name a substance in the envelope structure of some bacteria that can cause severe symptoms in humans.
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Identify 5 structures that may be contained in bacterial cytoplasm.
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Study Notes
Structures of Bacteria
- All bacteria have a cell membrane, cytoplasm, ribosomes, and one or few chromosomes.
- Most bacteria possess a cell wall and may have a surface coating called glycocalyx.
Structures Found in Some Bacteria
- Flagella: used for movement.
- Pili: tubular structures for conjugation, found in gram-negative bacteria.
- Fimbriae: small appendages for adhesion.
- S layer: protective protein layer formed in hostile environments.
- Slime layer: unorganized layer of polysaccharides/proteins for protection.
- Capsule: protective glycocalyx rich in carbohydrates linked to virulence.
Bacterial Shapes
- Coccus: spherical shape.
- Bacillus: cylindrical shape.
- Coccobacillus: short, thick oval rod.
- Vibrio: curved rod shape.
- Spirillum: rigid spiral shaped with external flagella.
- Spirochete: coiled spiral shape that moves flexibly using endoflagella.
Functionality of Flagella
- Chemotaxis: movement towards attractants or away from repellents.
- Flagellar receptors bind to molecules, triggering flagellar rotation.
- "Runs" are smooth movements towards stimuli; "tumbles" are directional changes.
Cell Wall Characteristics
- Gram-positive bacteria have a thick peptidoglycan layer, making their cell walls stronger than those of gram-negative bacteria.
- Gram-negative bacteria possess an outer membrane which can contribute to antibiotic resistance.
Health Risks of Bacterial Structures
- Gram-negative bacteria pose significant health risks due to their outer membrane and potential antibiotic resistance.
- Lipopolysaccharides in outer membranes can trigger severe immune responses, with Lipid A causing fever and shock.
Bacterial Cytoplasmic Structures
- Bacterial Chromosome: circular DNA containing essential genetic information.
- Plasmids: small, independent DNA molecules that replicate separately from the chromosome (not present in all bacteria).
- Ribosomes: sites for protein synthesis, coordinating mRNA with tRNA.
- Inclusions: storage bodies in the cytoplasm for various metabolic products.
- Microcompartments: specialized compartments for specific metabolic reactions.
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Description
Explore the essential structures and functionalities of bacteria, including their shapes, cell components, and the roles of flagella. This quiz covers bacterial morphology, including coccus, bacillus, and more, as well as specialized structures like pili and capsules. Test your knowledge on how these features contribute to bacterial survival and movement.
