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Questions and Answers
The cell wall of bacteria is primarily composed of ______.
The cell wall of bacteria is primarily composed of ______.
Peptidoglycan
Teichoic acid, together with lipoteichoic acid, constitutes the major surface antigen of Gram (+) organisms, such as in ______ pneumoniae.
Teichoic acid, together with lipoteichoic acid, constitutes the major surface antigen of Gram (+) organisms, such as in ______ pneumoniae.
Streptococcus
Gram-positive bacteria have many sheets of ______ that make up a large portion of their cell wall material.
Gram-positive bacteria have many sheets of ______ that make up a large portion of their cell wall material.
peptidoglycan
Teichoic acid binds ______ ion, which plays a role in the stability of the cell membrane.
Teichoic acid binds ______ ion, which plays a role in the stability of the cell membrane.
Teichoic acid is a water-soluble polymer found in the cell walls of ______ bacteria.
Teichoic acid is a water-soluble polymer found in the cell walls of ______ bacteria.
Teichoic acid is involved in the activation of ______ enzymes and determining susceptibility to autolytic activity.
Teichoic acid is involved in the activation of ______ enzymes and determining susceptibility to autolytic activity.
The tetrapeptide side chains are attached to N-acetylmuramic acid in the peptidoglycan's ______.
The tetrapeptide side chains are attached to N-acetylmuramic acid in the peptidoglycan's ______.
In Gram-negative bacteria, the unique amino acid found at position 3 of the tetrapeptide side chain is ______.
In Gram-negative bacteria, the unique amino acid found at position 3 of the tetrapeptide side chain is ______.
Replacement of choline by ethanolamine in the teichoic acid of Pneumococcus causes resistance to ______.
Replacement of choline by ethanolamine in the teichoic acid of Pneumococcus causes resistance to ______.
Gram-negative bacteria typically possess ______ sheets of peptidoglycan in their cell wall.
Gram-negative bacteria typically possess ______ sheets of peptidoglycan in their cell wall.
The outer membrane of Gram-negative bacteria is convoluted and contains ______ that serves transport and receptor functions.
The outer membrane of Gram-negative bacteria is convoluted and contains ______ that serves transport and receptor functions.
Lipopolysaccharides (LPS) are heat-stable and known to be lethally ______.
Lipopolysaccharides (LPS) are heat-stable and known to be lethally ______.
The composition of teichoic acid can vary based on the ______ medium.
The composition of teichoic acid can vary based on the ______ medium.
Common neutral sugars found in polysaccharides of the bacterial cell wall include Mannose, Arabinose, and ______.
Common neutral sugars found in polysaccharides of the bacterial cell wall include Mannose, Arabinose, and ______.
Lipid A is a complex ______ that acts as an endotoxin in Gram-negative bacteria.
Lipid A is a complex ______ that acts as an endotoxin in Gram-negative bacteria.
Polysaccharide in LPS represents a major surface antigen, known as the ______ antigen.
Polysaccharide in LPS represents a major surface antigen, known as the ______ antigen.
Glycerol enters prokaryotic cells by ______ diffusion.
Glycerol enters prokaryotic cells by ______ diffusion.
Group translocation facilitates the uptake of certain sugars, such as ______ and mannose.
Group translocation facilitates the uptake of certain sugars, such as ______ and mannose.
Phagocytosis involves the engulfment of solid particles through extensions called ______.
Phagocytosis involves the engulfment of solid particles through extensions called ______.
In pinocytosis, fluids and dissolved substances are taken into vesicles by ______ cell protrusions.
In pinocytosis, fluids and dissolved substances are taken into vesicles by ______ cell protrusions.
Excretion of hydrolytic enzymes helps break down larger food molecules such as proteins and ______.
Excretion of hydrolytic enzymes helps break down larger food molecules such as proteins and ______.
Hydrolytic enzymes are released into the ______ environment to aid in digestion.
Hydrolytic enzymes are released into the ______ environment to aid in digestion.
The site of carrier lipids for cell wall assembly is part of the ______ biosynthesis.
The site of carrier lipids for cell wall assembly is part of the ______ biosynthesis.
The cytoplasmic membrane contains enzymes such as ______ involved in the respiratory chain.
The cytoplasmic membrane contains enzymes such as ______ involved in the respiratory chain.
The O Antigen is derived from the German term 'Ohne ______' indicating its characteristic of being without film.
The O Antigen is derived from the German term 'Ohne ______' indicating its characteristic of being without film.
In a monotrichous arrangement, there is a single polar ______.
In a monotrichous arrangement, there is a single polar ______.
The term ______ refers to organisms that have no flagella.
The term ______ refers to organisms that have no flagella.
Axial filaments are composed of two fibrils that impart a ______, screw-like motion to the cell.
Axial filaments are composed of two fibrils that impart a ______, screw-like motion to the cell.
Pili are hair-like microfibrils that are shorter, thinner, and finer than ______.
Pili are hair-like microfibrils that are shorter, thinner, and finer than ______.
Sex pili are responsible for the attachment of ______ and recipient cells in bacterial conjugation.
Sex pili are responsible for the attachment of ______ and recipient cells in bacterial conjugation.
Each pilus is composed of protein subunits known as ______.
Each pilus is composed of protein subunits known as ______.
The axial filament occurs in the ______ space between the inner and outer membrane of the cell.
The axial filament occurs in the ______ space between the inner and outer membrane of the cell.
Endospores are highly resistant to ______, heat and chemical agents.
Endospores are highly resistant to ______, heat and chemical agents.
Endospores are formed when nutritional conditions become ______.
Endospores are formed when nutritional conditions become ______.
The germination process of endospores requires activation in a ______-rich medium.
The germination process of endospores requires activation in a ______-rich medium.
The heat resistance of the endospore is due in part to the presence of large amounts of ______ dipicolinate.
The heat resistance of the endospore is due in part to the presence of large amounts of ______ dipicolinate.
During the outgrowth process, the cell synthesizes ______ and RNA.
During the outgrowth process, the cell synthesizes ______ and RNA.
Metachromatic granules are the stored form of ______; they stain red with certain blue dyes.
Metachromatic granules are the stored form of ______; they stain red with certain blue dyes.
Polysaccharide granules are primarily composed of ______ and starch.
Polysaccharide granules are primarily composed of ______ and starch.
The germination of endospores requires water and germination agents such as the amino acid ______.
The germination of endospores requires water and germination agents such as the amino acid ______.
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Study Notes
Bacterial Cell Wall Composition
- High tensile strength attributed to peptidoglycan (Murein or Mucopeptide).
- Peptidoglycan differentiates bacteria into Gram-positive and Gram-negative types.
Gram-positive Bacteria
- Composed mainly of a thick peptidoglycan layer (40 sheets, 50-90% of cell wall material).
- Peptidoglycan structure includes:
- A backbone of alternating sugars: N-acetylglucosamine and N-acetylmuramic acid.
- Identical tetrapeptide side chains attached to N-acetylmuramic acid.
- Varying peptide cross bridges among species.
- Key positions in tetrapeptide:
- L-alanine at position 1.
- D-glutamate at position 2.
- D-alanine at position 4; variability at position 3.
- Teichoic acid:
- Water-soluble polymer linked to peptidoglycan.
- Functions as a surface antigen and binds magnesium ions for cell stability.
- Polysaccharides include neutral sugars (mannose, arabinose) and acidic sugars (glucuronic acid).
Gram-negative Bacteria
- Features an outer membrane (OM) with a complex structure:
- Contains phospholipids, proteins (matrix proteins and porins), and lipopolysaccharides (LPS).
- LPS is heat-stable, toxic, and significant for immune activation:
- Composed of Lipid A (endotoxin) and a polysaccharide known as "O" antigen.
- Outer membrane functions:
- Prevents leakage of periplasmic proteins.
- Facilitates transport of ions and small organic molecules.
- Engages in excretion of hydrolytic enzymes for nutrient breakdown.
Transport Mechanisms
- Facilitated diffusion allows certain compounds to enter prokaryotic cells efficiently.
- Active transport and group translocation are mechanisms used for nutrient uptake.
- Endocytosis includes phagocytosis (solid particles) and pinocytosis (fluids).
Bacterial Motility Structures
- Flagella types:
- Monotrichous (single polar), amphitrichous (flagella at both poles), lophotrichous (tuft at one pole), peritrichous (distributed around cell).
- Axial filament (endoflagellum) provides a screw-like motion to spirochetes.
- Pili (hairs):
- Composed of protein subunits (pilins), shorter than flagella, with roles in attachment and conjugation.
- Classes include ordinary pili (adhesion) and sex pili (bacterial conjugation).
Endospores
- Formed under unfavorable conditions (nutrient depletion).
- Highly resistant to extreme conditions (desiccation, heat, chemicals).
- Germination involves:
- Activation in nutrient-rich media.
- Initiation requiring water and germination agents.
- Outgrowth leads to active biosynthesis and cell division.
Inclusions - Granules
- Metachromatic granules store phosphate, stain red and indicate phosphate-rich environments.
- Polysaccharide granules store glycogen and starch; can be demonstrated with iodine staining.
- Lipid granules serve as storage material for lipids.
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