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Questions and Answers
What is characteristic of active transport processes across the cell membrane?
What is characteristic of active transport processes across the cell membrane?
What role do polymyxins play regarding bacterial cell membranes?
What role do polymyxins play regarding bacterial cell membranes?
Which of the following statements is true about the specificity of transport processes?
Which of the following statements is true about the specificity of transport processes?
How do polymyxins affect calcium and magnesium ions in relation to bacterial membranes?
How do polymyxins affect calcium and magnesium ions in relation to bacterial membranes?
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Which types of bacteria are polymyxins ineffective against?
Which types of bacteria are polymyxins ineffective against?
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What is NOT considered an essential structure in eubacteria?
What is NOT considered an essential structure in eubacteria?
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Which component is found in both Gram-positive and Gram-negative bacteria?
Which component is found in both Gram-positive and Gram-negative bacteria?
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What structure is specifically involved in bacterial movement?
What structure is specifically involved in bacterial movement?
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Which description best fits the function of the bacterial cell wall?
Which description best fits the function of the bacterial cell wall?
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Which statement is true regarding spore formation in bacteria?
Which statement is true regarding spore formation in bacteria?
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Which component is unique to Gram-negative bacteria?
Which component is unique to Gram-negative bacteria?
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What is the primary difference between Gram-positive and Gram-negative bacteria regarding their cell walls?
What is the primary difference between Gram-positive and Gram-negative bacteria regarding their cell walls?
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Which internal structure is responsible for protein synthesis in bacteria?
Which internal structure is responsible for protein synthesis in bacteria?
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What is one of the primary functions of teichoic acids in Gram positive bacteria?
What is one of the primary functions of teichoic acids in Gram positive bacteria?
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Which component is covalently linked to N-acetylmannosamine in the disaccharide unit of wall teichoic acids?
Which component is covalently linked to N-acetylmannosamine in the disaccharide unit of wall teichoic acids?
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What type of bond connects the main chain polymer of lipoteichoic acids to the glycolipid anchor?
What type of bond connects the main chain polymer of lipoteichoic acids to the glycolipid anchor?
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Which of the following describes a primary function of wall teichoic acids?
Which of the following describes a primary function of wall teichoic acids?
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What is a characteristic feature of atypical cell walls such as that of mycobacterium?
What is a characteristic feature of atypical cell walls such as that of mycobacterium?
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How do teichoic acids contribute to antibiotic resistance in Gram positive bacteria?
How do teichoic acids contribute to antibiotic resistance in Gram positive bacteria?
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What percentage of the weight of the cell wall do teichoic acids constitute?
What percentage of the weight of the cell wall do teichoic acids constitute?
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Which of the following is a property of wall teichoic acid?
Which of the following is a property of wall teichoic acid?
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What is the primary composition of the prokaryotic plasma membrane?
What is the primary composition of the prokaryotic plasma membrane?
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How does the protein-to-phospholipid ratio in a prokaryotic plasma membrane compare?
How does the protein-to-phospholipid ratio in a prokaryotic plasma membrane compare?
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What role do mesosomes play in prokaryotic cells?
What role do mesosomes play in prokaryotic cells?
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Which of the following is a function of the plasma membrane?
Which of the following is a function of the plasma membrane?
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What type of transport allows molecules to move across the membrane based on concentration gradients?
What type of transport allows molecules to move across the membrane based on concentration gradients?
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Which statement accurately describes the nature of the prokaryotic plasma membrane?
Which statement accurately describes the nature of the prokaryotic plasma membrane?
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What is the significance of alcohols or certain antibiotics to the plasma membrane?
What is the significance of alcohols or certain antibiotics to the plasma membrane?
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What type of proteins reside on the inner or outer leaflets of the plasma membrane?
What type of proteins reside on the inner or outer leaflets of the plasma membrane?
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What structural feature distinguishes mycoplasmas from other bacteria?
What structural feature distinguishes mycoplasmas from other bacteria?
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Which type of treatment can induce the formation of L-forms in bacteria?
Which type of treatment can induce the formation of L-forms in bacteria?
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What is the primary characteristic of the periplasmic space in gram-negative bacteria?
What is the primary characteristic of the periplasmic space in gram-negative bacteria?
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What type of L-form is a wall-less Gram-positive cell?
What type of L-form is a wall-less Gram-positive cell?
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Which of the following proteins is NOT found in the periplasmic space of gram-negative bacteria?
Which of the following proteins is NOT found in the periplasmic space of gram-negative bacteria?
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Which condition could lead to the rupture of L-forms?
Which condition could lead to the rupture of L-forms?
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What is a characteristic of spheroplasts compared to protoplasts?
What is a characteristic of spheroplasts compared to protoplasts?
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What major component do archaea lack in their cell walls that is typically found in bacteria?
What major component do archaea lack in their cell walls that is typically found in bacteria?
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What is the role of the third amino acid in the tetrapeptide chain attached to NAM in peptidoglycan?
What is the role of the third amino acid in the tetrapeptide chain attached to NAM in peptidoglycan?
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Which antibiotic inhibits the MurA enzyme during the biosynthesis of peptidoglycan?
Which antibiotic inhibits the MurA enzyme during the biosynthesis of peptidoglycan?
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Which process directly links the tetrapeptides in the peptidoglycan structure?
Which process directly links the tetrapeptides in the peptidoglycan structure?
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What is the effect of β-lactams on the biosynthesis of peptidoglycan?
What is the effect of β-lactams on the biosynthesis of peptidoglycan?
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What function do autolysins serve in the context of peptidoglycan synthesis?
What function do autolysins serve in the context of peptidoglycan synthesis?
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What amino acids are typically present in the tetrapeptide attached to NAM?
What amino acids are typically present in the tetrapeptide attached to NAM?
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How does D-Cycloserine affect peptidoglycan biosynthesis?
How does D-Cycloserine affect peptidoglycan biosynthesis?
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What is the role of bactoprenol in the peptidoglycan synthesis process?
What is the role of bactoprenol in the peptidoglycan synthesis process?
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Study Notes
Pathogenic Microorganisms 222 PHARM
- Course covers pathogenic microorganisms.
- The presentation details bacterial structures and functions.
Bacterial Structures and Function
- Objectives include microscopic bacterial structure details, distinguishing Gram-positive and Gram-negative cell walls, describing bacterial movement, and spore formation.
Bacterial Structure
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Bacteria consist of both essential and additional structures.
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Essential: cell wall, cell membrane, cytoplasm, ribosomes, and nuclear material.
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Additional (non-essential): capsule, slime layer, flagella, pili, fimbriae, inclusions, spores, and plasmids.
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A diagram shows Gram-positive and Gram-negative structures.
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Gram-positive: thicker peptidoglycan layer and teichoic acids; no outer membrane.
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Gram-negative: thinner peptidoglycan layer, outer membrane, and lipopolysaccharides (LPS); periplasmic space between layers.
Structure of Eubacteria
- External structures (extracytoplasmic): glycocalyx, flagella, pili, and fimbriae.
- Cell envelope: outer membrane, cell wall, and cell membrane.
- Internal structures (intracytoplasmic): cytoplasm, ribosomes, nuclear material, inclusions, spores, and plasmids.
Cell Wall Structures
- Key components: outer membrane, peptidoglycan, teichoic acids, and periplasm.
- Cytoplasmic membrane (CM) is also included.
- Gram positive and Gram negative cell wall composition differ significantly.
Cell Wall (CW)
- The CW is the outermost component of bacteria, external to the cytoplasmic membrane.
- Highly rigid and plays a role in shaping the cell.
- Thickness and composition vary based on bacterial type.
- Two major types: Gram-positive and Gram-negative.
- Diagram illustrating gram positive and gram negative
- Gram-positive has a thick layer; Gram-negative a thin layer.
- LPS and porins, components of gram negative, not present in gram positive cell walls.
- Diagram illustrating gram positive and gram negative
Gram Positive and Gram Negative Cell Wall
- Summarized comparison of Gram-positive and Gram-negative cell walls.
- Presence/absence of outer membrane, peptidoglycan thickness, presence of teichoic acids.
- The table shows variations in thickness (Gram+ vs. Gram-), layers, and other component presences in the walls.
Outer Membrane (OM)
- Present only in Gram-negative bacteria, outside peptidoglycan layer.
- Asymmetric lipid bilayer: composed of LPS, porins, phospholipids, and lipoproteins.
Lipopolysaccharides (LPS)
- Hydrophilic, extends into cell exterior, and highly variable between species.
- A specific type of immunogenic O-antigen found on E. coli (O157:H7).
- Includes an O-antigen, core oligosaccharide, and lipid A.
- Lipid A is hydrophobic endotoxin/pyrogen.
Porins Proteins
- Membrane proteins forming channels, found in both halves of the OM.
- Responsible for transporting hydrophilic molecules.
- Loss of porins can lead to antibiotic resistance.
- Other associated proteins, like OmpA, serve as receptors and stabilizers
Lipoteichoic Acids
- Play a role in stabilizing OM structure, covalently bonded to peptidoglycan, and anchoring inner membrane leaflet.
Phospholipids
- OM inner leaflet resembles the cytoplasmic membrane (CM); outer leaflet contains LPS.
Functions of OM
- Conferring negative charge to cells
- Maintaining bacterial structure
- Providing protection against adverse conditions
- Acting as channels through OmpC and OmpF
- Binding receptors for some viruses and aiding mating conjugation
- Initiating innate immune responses.
Peptidoglycan (PDG)
- Found in all eubacteria, surrounding the cytoplasmic membrane (CM).
- Highly rigid structure that prevents osmotic lysis.
- Maintains cell shape, permeable to ions, amino acids, and sugars.
- Composed of repeating disaccharide units (NAG and NAM) linked by short peptides.
- Cross-linking of peptide chains occurs between different layers via 3rd amino acid.
- Specific peptides link specific organisms.
- Cross-linking is essential for rigidity.
Teichoic Acids (TA)
- Found only in Gram-positive bacteria, contributing to 50% of the cell wall weight.
- Cell surface anionic glycopolymers.
- Responsible for negative charge.
- Highly immunogenic.
- Mediate adherence to mucosal cells.
- WTA and LTA are two key types.
- Two-part structure (disaccharide unit) made of N-acetylmannosamine and NAG-1-phosphate.
Types of Teichoic Acids
- WTA (Wall Teichoic Acid): main chain of glycerol or ribitol linked by phosphodiester bond.
- LTA (Lipoteichoic Acid): linked to cytoplasmic membrane with glycolipid anchor.
- Cell shape determination and regulation, along with pathogenesis and antibiotic resistance are all contributed to by these two types.
Atypical Cell Walls
- Acid-fast bacteria (e.g., Mycobacterium): have a high lipid content (up to 60%) with mycolic acids in their cell walls.
- Mycolic acids are long-chain fatty acids covalently bound to peptidoglycan.
- Additional components, such as mannan caps, lipoproteins, and other proteins create a thick waxy layer for protection.
- Mycolic acids are long-chain fatty acids covalently bound to peptidoglycan.
Wall-less (Cell Walls Deficient) Bacteria
- Mycoplasmas, Archaea, and L-forms lack cell walls.
- Mycoplasmas have sterols in their plasma membrane.
- Archaea have pseudomurein walls (different structure than peptidoglycan).
- L-forms lose cell walls under certain conditions and can reacquire them.
L-Forms
- Defective cell wall bacteria.
- Induced artificially via lysozyme digestion, penicillin treatment, or hypertonic solutions.
- Two types: protoplasts (wall-less Gram-positive) and spheroplasts (wall-less Gram-negative).
- Protoplasts and spheroplasts are remarkably stable, able to divide normally, and have great plasticity and resilience to survive and restore cell walls in different conditions.
Periplasmic Space (periplasm)
- In Gram-negative bacteria, space between the outer and cytoplasmic membranes.
- Contains enzymes and gel-like solution of proteins.
- Includes biosynthetic enzymes, binding proteins for transporting molecules, and enzymes degrading antibiotics.
Plasma Membrane
- Encloses the cytoplasm, selectively permeable, and less rigid than eukaryotic cell membranes.
- Mostly composed of phospholipids.
- Proteins embedded in the phospholipid bilayer regulate transport, metabolism, and other functions.
- No sterols in most bacterial PMs with exception of mycoplasma.
- Proteins and phospholipids are present in a 3:1 ratio in the membrane.
Mesosomes
- Invaginations of the cytoplasmic membrane, crucial for cell wall formation during cell division.
- Involved in oxidative phosphorylation.
Functions of Plasma Membrane
- Selective permeability: semipermeable nature of the membrane allows controlled passage of molecules. - Contains carrier proteins that aid in transport activities.
- Regulation of cell division: crucial for proper bacterial multiplication.
- Excretion of proteins like IgA protease is vital for bacterial virulence and immune evasion.
- Contains enzymes for ATP production and oxidative phosphorylation processes.
- Damage to plasma membrane by antibiotics and other factors can lead to cell leakage.
- Excretion of proteins like IgA protease is vital for bacterial virulence and immune evasion.
Transport Across the Cell Membrane
- Key rule is movement from high to low concentration.
- Diffusion describes the spontaneous process.
- Passive transport/facilitated diffusion are crucial transport mechanisms depending if energy is required. Transport via carrier proteins and channels are also prominent means of transport.
Types of Transport
- Based on energy use: passive (no energy) vs active (energy required). - Various mechanisms including uniporters, symporters, and antiporters for directed transport.
Antibiotics Action on Cell Membrane
- Polymyxins act by electrostatic interaction with negatively charged lipids in the OM.
- Can destabilize the membrane, increase permeability, causing leakage, and cell death.
- Inhibition of type II NADH oxidoreductase is another mechanism.
- Primarily acts on Gram-negative bacteria but has varying effects on other bacterial cell types.
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Description
Explore the world of pathogenic microorganisms with a focus on bacterial structures and functions. This quiz will help you distinguish between Gram-positive and Gram-negative bacteria, understand their essential and additional structures, and learn about their movements and spore formation.
