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Questions and Answers
What is the main function of the cell wall in bacterial cells?
What is the main function of the cell wall in bacterial cells?
Which structure in bacterial cells lacks sterols, as opposed to eukaryotic cells?
Which structure in bacterial cells lacks sterols, as opposed to eukaryotic cells?
What is the role of membrane-associated proteins in bacterial cells?
What is the role of membrane-associated proteins in bacterial cells?
Which component allows the differentiation of the two main groups of bacteria?
Which component allows the differentiation of the two main groups of bacteria?
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What is the function of peptidoglycan in the cell wall of bacteria?
What is the function of peptidoglycan in the cell wall of bacteria?
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Which structure is responsible for stabilizing the bacterial membrane?
Which structure is responsible for stabilizing the bacterial membrane?
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What is the main function of the cytoplasmic or plasma membrane in bacterial cells?
What is the main function of the cytoplasmic or plasma membrane in bacterial cells?
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Which structure is NOT found in bacterial cells?
Which structure is NOT found in bacterial cells?
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What is a unique feature of the cytoplasmic membrane in bacterial cells compared to eukaryotic cells?
What is a unique feature of the cytoplasmic membrane in bacterial cells compared to eukaryotic cells?
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Which component is responsible for electron transport during bacterial respiration?
Which component is responsible for electron transport during bacterial respiration?
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Which component of the bacterial cell envelope is only found in Gram-negative bacteria?
Which component of the bacterial cell envelope is only found in Gram-negative bacteria?
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What is the function of transporter proteins in bacterial cells?
What is the function of transporter proteins in bacterial cells?
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Which bacterial species lack a cell wall and are considered the smallest bacteria described?
Which bacterial species lack a cell wall and are considered the smallest bacteria described?
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What is the function of a bacterial capsule?
What is the function of a bacterial capsule?
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Which structure in bacterial cells is responsible for locomotion or motility?
Which structure in bacterial cells is responsible for locomotion or motility?
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What is the main function of pili/fimbriae in bacterial cells?
What is the main function of pili/fimbriae in bacterial cells?
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Which state represents a cryptobiotic state of dormancy in some Gram-positive bacteria?
Which state represents a cryptobiotic state of dormancy in some Gram-positive bacteria?
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What is the role of mycolic acids in the bacterial envelope?
What is the role of mycolic acids in the bacterial envelope?
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In bacterial cells, what does the periplasmic space contain?
In bacterial cells, what does the periplasmic space contain?
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Which component of the bacterial cell structure acts as an immunogenic molecule known as endotoxin?
Which component of the bacterial cell structure acts as an immunogenic molecule known as endotoxin?
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What is the main function of plasmids in bacterial cells?
What is the main function of plasmids in bacterial cells?
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Which of the following components is NOT found in all bacterial cells?
Which of the following components is NOT found in all bacterial cells?
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What is the function of ribosomes in bacterial cells?
What is the function of ribosomes in bacterial cells?
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In a bacterial cell, where is the DNA primarily located?
In a bacterial cell, where is the DNA primarily located?
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Which of the following is NOT a component of the bacterial envelope?
Which of the following is NOT a component of the bacterial envelope?
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What distinguishes prokaryotic cells from eukaryotic cells?
What distinguishes prokaryotic cells from eukaryotic cells?
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Study Notes
Bacterial Cell Structure
- Cytoplasmic membrane: Flexible structure composed of phospholipids and proteins, no sterols, with hydrophilic outer faces and hydrophobic interior.
- Membrane-associated proteins: Stabilize membrane, transport molecules, and facilitate electron transport for respiration, and contain enzymes.
Cell Wall (Peptidoglycan Layer)
- Peptidoglycan: Chain of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) crosslinked with short peptides.
- Functions: Protection against mechanical damage and osmotic lysis, non-selective transport, and differences in structure and chemical composition affect pathogenicity and staining properties.
Bacterial Envelope
- Allows characterization of two main groups of bacteria: Gram-positive and Gram-negative.
- Gram-staining technique: Gram-negative bacteria have an outer membrane, while Gram-positive bacteria do not.
Alternative Structural Bacterial Envelopes
- Mycobacteria: Contains mycolic acids, has a thick waxy hydrophobic cell wall, and is acid-fast for identification.
- Mollicutes (Mycoplasma): Lack a cell wall (peptidoglycan layer), are highly pleomorphic and osmotically unstable, and are the smallest bacteria described.
Capsule (Glycocalyx)
- Extracellular polymeric matrix present in some bacterial species.
- Functions: Protection (environment, phagocytosis), cell adherence, and nutrient reserve.
Flagella
- Anchored to the bacterial cell envelope, multi-protein structure with varied number and position between bacteria.
- Functions: Locomotion or bacterial motility.
Pili/Fimbriae
- Fine, straight, hair-like appendages attached to the cell wall, known as “adhesins”.
- Functions: Adhesion to host tissues (specificity) and contribute to antigenicity.
Endospores
- Cryptobiotic state of dormancy and most durable type of cell found in nature.
- Produced by some Gram-positive bacteria, ensuring survival during adverse environmental conditions.
Bacterial Characteristics
- Bacteria are ubiquitous, essential for life on Earth, and have diverse morphologies and arrangements.
- Sizes range from 1 µm to 5 µm in diameter, with the largest bacterium known being Thiomargarita magnifica (2.0 cm long).
Cell Structure
- Prokaryotes: Unicellular organisms lacking membranous organelles and true nucleus.
- All bacteria have cytoplasm, ribosomes, nucleoid (DNA), and plasma membrane, while some have additional structures.
Nucleoid
- Contains the bacterial chromosome, a double-stranded DNA that is mostly single (haploid) and circular.
- Functions: Contains essential genes for bacterial life (core-genome).
Plasmid
- Circular DNA molecule containing additional genes that are not essential for bacterial life.
- Functions: Provide virulence factors (genes), antibiotic resistance (genes), and other genes.
Ribosomes
- Cellular protein factory composed of proteins and rRNA with two subunits (large 50S and small 30S).
- Functions: Applications in therapy and phylogeny.
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Description
Test your knowledge on the components of a bacterial cell structure including the cytoplasmic membrane, membrane-associated proteins, and cell wall. Learn about the characteristics and functions of each component.
