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What structure in bacteria is primarily responsible for energy production in the form of ATP?
What structure in bacteria is primarily responsible for energy production in the form of ATP?
The plasma membrane is responsible for energy production via ATP synthesis.
Identify two types of stored nutrients found in bacterial cells.
Identify two types of stored nutrients found in bacterial cells.
Stored nutrients in bacterial cells may include glycogen and lipids.
What are the roles of the cytoskeleton in bacterial cells?
What are the roles of the cytoskeleton in bacterial cells?
The cytoskeleton helps in cell division and maintaining cell shape.
What occurs when bacteria encounter unfavorable conditions, such as starvation or heat?
What occurs when bacteria encounter unfavorable conditions, such as starvation or heat?
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List three functions of the bacterial cell wall.
List three functions of the bacterial cell wall.
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What is the difference between a capsule and a slime layer in bacterial cells?
What is the difference between a capsule and a slime layer in bacterial cells?
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What role does the glycocalyx play in bacteria?
What role does the glycocalyx play in bacteria?
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What is the composition of bacterial ribosomes, and why are they significant?
What is the composition of bacterial ribosomes, and why are they significant?
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Describe the primary function of the plasma membrane in bacterial cells.
Describe the primary function of the plasma membrane in bacterial cells.
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What is the significance of H antigens in bacteria?
What is the significance of H antigens in bacteria?
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How do antibiotics that cause osmotic lysis affect bacterial cells?
How do antibiotics that cause osmotic lysis affect bacterial cells?
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What are the main components of the bacterial cell wall?
What are the main components of the bacterial cell wall?
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What are the functions of sex pili in bacteria?
What are the functions of sex pili in bacteria?
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What are the key differences between Gram-positive and Gram-negative bacteria regarding their cell wall structure?
What are the key differences between Gram-positive and Gram-negative bacteria regarding their cell wall structure?
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What role does peptidoglycan play in bacterial cells?
What role does peptidoglycan play in bacterial cells?
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Describe the characteristics of cocci and bacilli bacteria.
Describe the characteristics of cocci and bacilli bacteria.
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What is the significance of lipopolysaccharides (LPS) in Gram-negative bacteria?
What is the significance of lipopolysaccharides (LPS) in Gram-negative bacteria?
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Explain the concept of monomorphic and pleomorphic bacteria.
Explain the concept of monomorphic and pleomorphic bacteria.
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What is the function of flagella in bacterial cells?
What is the function of flagella in bacterial cells?
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What is the difference between protoplasts and spheroplasts?
What is the difference between protoplasts and spheroplasts?
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How do lysozyme and the presence of L-forms relate to bacterial cell walls?
How do lysozyme and the presence of L-forms relate to bacterial cell walls?
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What type of bacteria are known for forming endospores in response to unfavorable conditions?
What type of bacteria are known for forming endospores in response to unfavorable conditions?
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What structures are contained within bacterial cells that help with cell division and maintaining shape?
What structures are contained within bacterial cells that help with cell division and maintaining shape?
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What is the main characteristic that separates Gram-positive bacteria from Gram-negative bacteria?
What is the main characteristic that separates Gram-positive bacteria from Gram-negative bacteria?
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What cellular structure in bacteria contains nucleoid and ribosomes but lacks a true nucleus?
What cellular structure in bacteria contains nucleoid and ribosomes but lacks a true nucleus?
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What is the purpose of the metachromatic granules found in certain bacterial cells?
What is the purpose of the metachromatic granules found in certain bacterial cells?
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What is the role of the glycocalyx in bacterial adhesion to human tissues?
What is the role of the glycocalyx in bacterial adhesion to human tissues?
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How do flagella contribute to bacterial motility?
How do flagella contribute to bacterial motility?
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Describe the composition of bacterial ribosomes and their significance in protein synthesis.
Describe the composition of bacterial ribosomes and their significance in protein synthesis.
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What distinguishes an encapsulated bacterium from a non-encapsulated one, particularly in relation to phagocytosis?
What distinguishes an encapsulated bacterium from a non-encapsulated one, particularly in relation to phagocytosis?
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Explain the function and composition of the plasma membrane in bacterial cells.
Explain the function and composition of the plasma membrane in bacterial cells.
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What is the significance of antigenic properties such as K and H antigens in bacteria?
What is the significance of antigenic properties such as K and H antigens in bacteria?
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How does the structure of the bacterial cell wall contribute to its function?
How does the structure of the bacterial cell wall contribute to its function?
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What are the unique features of Mycoplasma that differentiate them from other bacteria regarding their plasma membrane?
What are the unique features of Mycoplasma that differentiate them from other bacteria regarding their plasma membrane?
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What defines acid-fast bacteria, and how do they stain compared to non-acid-fast bacteria?
What defines acid-fast bacteria, and how do they stain compared to non-acid-fast bacteria?
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How does the structure of Gram-positive bacteria differ from that of Gram-negative bacteria regarding peptidoglycan?
How does the structure of Gram-positive bacteria differ from that of Gram-negative bacteria regarding peptidoglycan?
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What role do teichoic acids play in the structure of Gram-positive bacteria?
What role do teichoic acids play in the structure of Gram-positive bacteria?
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Explain the consequences of lysozyme's action on bacterial cells.
Explain the consequences of lysozyme's action on bacterial cells.
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What are the primary components of lipopolysaccharides (LPS) in Gram-negative bacteria, and why are they significant?
What are the primary components of lipopolysaccharides (LPS) in Gram-negative bacteria, and why are they significant?
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Describe the implications of bacterial size variability, particularly in the context of pathogenicity.
Describe the implications of bacterial size variability, particularly in the context of pathogenicity.
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What distinguishes monomorphic bacteria from pleomorphic bacteria?
What distinguishes monomorphic bacteria from pleomorphic bacteria?
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How does the presence of a glycocalyx influence bacterial virulence?
How does the presence of a glycocalyx influence bacterial virulence?
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Study Notes
Bacterial Cell Structure
- Medical microbiology studies microbes and their interactions with hosts, leading to infectious diseases.
- Cocci are round.
- Rod-shaped bacilli may have tapered ends, like cigars or be oval. Coccobacilli are cocci-shaped bacilli.
- Spiral bacteria have one or more twists.
- Bacteria have diverse shapes: Cocci, Coccobacilli, Vibrio, Bacillus, Spirillum, Spirochete.
- Monomorphic bacteria have a single shape.
- Pleomorphic bacteria have many shapes.
- Bacterial sizes range from 0.2 to 5 micrometers (µm).
- A micron (µm) is one-thousandth of a millimeter.
Bacterial Cell Shape and Arrangement
- Diagrams displaying various arrangements of bacteria (diplococci, streptococci, tetrads, sarcinae, staphylococci, diplobacilli, streptobacilli, vibrio, spirillum, spirochete) are shown.
- SEM (Scanning Electron Micrographs) images are also included showing different arrangements.
Structures External to the Cell Wall
- Glycocalyx (capsule/slime layer) is a gelatinous polysaccharide or polypeptide layer surrounding the cell wall.
- Capsule is firmly attached.
- Slime layer is loosely attached.
- Functions include protection from phagocytosis, antigenicity (K antigen), and adherence to surfaces.
- Flagella are long helical structures made of protein flagellin. They anchor in the cell membranes. They are organs of motility, allowing bacteria to move towards nutrients and other attractants (chemotaxis). They are also antigenic (H antigen).
- Fimbriae and pili help bacteria adhere to surfaces or other bacteria.
Structures Internal to the Cell Wall
- Cytoplasm is a thick, transparent substance within the plasma membrane.
- Nucleoid is the area containing the circular DNA.
- Cytoplasmic membrane is a thin, elastic membrane beneath the cell wall; it is composed of phospholipids and proteins.
- Ribosomes are the primary sites for protein synthesis (translation).
- Inclusions are stored nutrients (proteins, lipids, glycogen), and include structures like metachromatic granules (in C. diphtheriae). These are observed using a methylene blue stain.
Cell Wall
- The cell wall is external to the cytoplasmic membrane and provides support and rigidity to the cell. It's composed of peptidoglycan in all bacteria except Mycoplasma.
- Peptidoglycan is composed of N-acetylglucosamine and N-acetylmuramic acid. It is found in both Gram-positive and Gram-negative bacteria.
- Gram-positive bacteria have a thick peptidoglycan layer with teichoic acids located outside the layer.
- Gram-negative bacteria have a thin peptidoglycan layer situated between the outer and cytoplasmic membranes. The outer membrane contains lipopolysaccharides (LPS, endotoxin), lipoproteins, and phospholipids. The periplasmic space is between the outer and cytoplasmic membranes. Enzymes like β-lactamases are present in this space.
Gram-Positive and Gram-Negative Cell Walls: Key Differences
- Gram-positive cell walls (thick): teichoic acids are outside the peptidoglycan layer.
- Gram-negative cell walls (thin): an outer membrane with lipopolysaccharides (LPS) and lipoproteins surrounds the peptidoglycan layer. Periplasmic space is between the outer and cell membranes.
Cell Wall Function
- Supports and maintains cell shape.
- Is involved in the gram staining reaction.
- Responsible for bacterial toxicity due to LPS.
- Serves as a target for many antibiotics.
Atypical Cell Walls
- Acid-fast bacteria are resistant to some dyes due to a waxy lipid layer surrounding peptidoglycans.
- Mycoplasmas lack cell walls and are resistant to antibiotics that target cell walls.
- L-forms of some bacteria lose cell walls and maintain some functions.
Bacterial Endospores
- Some bacteria form endospores during conditions like starvation, desiccation, and heat.
- Endospores are extremely resistant structures.
- Endospores function in survival and reproduction under harsh conditions.
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