Peptidoglycans of Bacterial Cell Walls
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Questions and Answers

What is the primary component of bacterial cell walls?

  • Peptidoglycan (correct)
  • Protein
  • Polysaccharide
  • Peptide

    • What is the function of the interpeptide bridges in peptidoglycan?

  • Regulate cell growth and division
  • Connecting peptidoglycan chains (correct)
  • Stabilize the cell membrane
  • Provide structural support to the cell

    • What is the primary function of the periplasmic space?

  • Waste and toxin removal
  • Nutrient uptake and metabolism
  • Cell signaling and communication
  • Cell wall synthesis and modification (correct)

    • Which type of bacteria has a wall profile intermediate between gram-positive and gram-negative formats?

    <p>Gram-variable bacteria</p> Signup and view all the answers

    What is the outermost layer of the cell wall in Methanococcus voltae?

    <p>S-layer</p> Signup and view all the answers

    Which of the following is not a component of peptidoglycan?

    <p>Lipids</p> Signup and view all the answers

    What is the role of the L-alanine in peptidoglycan?

    <p>N-terminal amino acid</p> Signup and view all the answers

    What is the term for the space between the outer and plasma membranes?

    <p>Periplasm</p> Signup and view all the answers

    What is the primary function of the cell membrane in bacterial cells?

    <p>To serve as a permeability barrier</p> Signup and view all the answers

    What is the orientation of phospholipid molecules in the cytoplasmic membrane?

    <p>Hydrophobic ends facing inward and hydrophilic ends facing outward</p> Signup and view all the answers

    What type of proteins are present in the membrane layer to facilitate transport?

    <p>Transport proteins</p> Signup and view all the answers

    What is the primary component of yeast cell walls?

    <p>Mannan</p> Signup and view all the answers

    Which of the following is NOT a component of the cytoplasmic membrane?

    <p>Nucleic acids</p> Signup and view all the answers

    What is the purpose of Lipid X in the synthesis of the cytoplasmic membrane?

    <p>To participate in the formation of disaccharide 1-P</p> Signup and view all the answers

    What is the function of peptidoglycan in bacterial cell walls?

    <p>Provides structural rigidity</p> Signup and view all the answers

    What is the product of the reaction catalyzed by the enzyme lpxB?

    <p>Lipid IVA</p> Signup and view all the answers

    What is the primary component of the cell wall in filamentous fungi?

    <p>Chitin</p> Signup and view all the answers

    What is the outermost component of the cell surface in many archaebacteria?

    <p>S-layer</p> Signup and view all the answers

    What is the energy source required for the synthesis of the cytoplasmic membrane?

    <p>ATP</p> Signup and view all the answers

    Which of the following is NOT a component of yeast cell walls?

    <p>Peptidoglycan</p> Signup and view all the answers

    What is the function of the enzyme kdtA in the synthesis of the cytoplasmic membrane?

    <p>To catalyze the formation of Lipid IVA</p> Signup and view all the answers

    What is the role of the S-layer in gram-negative bacteria?

    <p>Is attached to the outer membrane</p> Signup and view all the answers

    What is the hallmark of the eubacteria?

    <p>Production of peptidoglycan</p> Signup and view all the answers

    What is the composition of the S-layer in archaea?

    <p>Both protein and glycoprotein</p> Signup and view all the answers

    What is the main difference between prokaryotic and eukaryotic cells?

    <p>Eukaryotic cells have a distinct nucleus</p> Signup and view all the answers

    What is the main function of the nucleus in eukaryotic cells?

    <p>To regulate the cell's biochemical and hereditary processes</p> Signup and view all the answers

    Which of the following eukaryotes have a discrete membrane-bound nucleus?

    <p>All of the above</p> Signup and view all the answers

    What is the characteristic of the nuclear membrane in eukaryotic cells?

    <p>It is composed of at least two distinct layers</p> Signup and view all the answers

    Which eukaryote has a double-layered nuclear membrane with pores?

    <p>Acyria cinerea</p> Signup and view all the answers

    What is the organizational center of eukaryotic cells?

    <p>Nucleus</p> Signup and view all the answers

    What is the role of the pores in the nuclear membrane?

    <p>To regulate the movement of substances into and out of the nucleus</p> Signup and view all the answers

    Which of the following is a characteristic of eukaryotic cells?

    <p>Presence of a distinct nucleus</p> Signup and view all the answers

    What is the type of flagella present in Archaebacteria?

    <p>Rotating flagella</p> Signup and view all the answers

    Which of the following eukaryotes has undulating flagella or cilia?

    <p>All of the above</p> Signup and view all the answers

    What is the characteristic of flagella in Lower Eukaryotes?

    <p>They are undulating</p> Signup and view all the answers

    Which of the following is NOT a characteristic of flagella in Metazoan?

    <p>They are rotating</p> Signup and view all the answers

    What is the function of flagella in eukaryotic cells?

    <p>Cell movement</p> Signup and view all the answers

    Which of the following eukaryotes lacks flagella or cilia?

    <p>None of the above</p> Signup and view all the answers

    What is the term for the hair-like structures present in some eukaryotic cells?

    <p>Cilia</p> Signup and view all the answers

    Which of the following is a characteristic of flagella in Fungi?

    <p>They are undulating</p> Signup and view all the answers

    What is the difference between flagella and cilia?

    <p>Cilia are shorter than flagella</p> Signup and view all the answers

    Which of the following statements about flagella is TRUE?

    <p>Only Archaebacteria have rotating flagella</p> Signup and view all the answers

    What is the term used to describe the DNA-containing region of the cell in bacteria?

    <p>Nucleoid</p> Signup and view all the answers

    What can be seen in the nuclear membrane of eukaryotic cells?

    <p>Pores</p> Signup and view all the answers

    Which organelle is responsible for protein synthesis in eukaryotic cells?

    <p>Endoplasmic reticulum</p> Signup and view all the answers

    What is the function of the rough endoplasmic reticulum?

    <p>Protein modification and transport</p> Signup and view all the answers

    Which of the following is a feature of bacterial cell structure?

    <p>Cell wall</p> Signup and view all the answers

    What is the term used to describe the region between the nucleus and the plasmalemma in eukaryotic cells?

    <p>Cytoplasm</p> Signup and view all the answers

    Which of the following is NOT a feature of eukaryotic cell structure?

    <p>Cell wall</p> Signup and view all the answers

    What is the term used to describe the process of protein synthesis in eukaryotic cells?

    <p>Translation</p> Signup and view all the answers

    What is thought to facilitate rapid cell doubling during fast growth in bacteria?

    <p>Multiple copies of nucleoids or entire chromosomes</p> Signup and view all the answers

    What has been shown to direct the oriC region toward the poles in some bacteria?

    <p>Protein components of a chromosomal segregation apparatus</p> Signup and view all the answers

    What is a characteristic of fast-growing bacterial cells harvested and fixed for observation under the electron microscope?

    <p>Multiple nucleoids</p> Signup and view all the answers

    What type of movement of immunolabeled nucleoids has been observed during replication and cell division in bacteria?

    <p>Mitosis-like</p> Signup and view all the answers

    What is thought to occur during the S phase in fast-growing bacterial cells?

    <p>Nucleoid segregation</p> Signup and view all the answers

    What has been suggested to participate in a mitosis-like mechanism that effects nucleoid segregation in some bacteria?

    <p>Other systems</p> Signup and view all the answers

    What is a characteristic of nucleoids in fast-growing bacterial cells?

    <p>Multiple copies of chromosomes</p> Signup and view all the answers

    What is the term used to describe the region containing the DNA in bacterial cells?

    <p>Nucleoid</p> Signup and view all the answers

    What is the function of the H-NS protein in bacteria?

    <p>To structure the nucleoid region</p> Signup and view all the answers

    Which of the following proteins is involved in curved DNA binding in bacteria?

    <p>CbpA and CbpB</p> Signup and view all the answers

    What is the name of the histone-like protein found in Archaea?

    <p>Histone-like protein</p> Signup and view all the answers

    What is the characteristic of protein-associated DNA regions in Halobacterium salinarum?

    <p>Nucleosome-like fibrous structures</p> Signup and view all the answers

    What is the primary function of mitochondria in eukaryotic cells?

    <p>Oxidative metabolism</p> Signup and view all the answers

    Which of the following proteins is an inhibitor of chromosome initiation in bacteria?

    <p>IciA</p> Signup and view all the answers

    What is the function of the Fis protein in bacteria?

    <p>Factor for inversion stimulation</p> Signup and view all the answers

    Which of the following proteins is involved in the suppression of td mutant phenotype in bacteria?

    <p>StpA</p> Signup and view all the answers

    What is the role of Fis in chromosomal DNA replication?

    <p>Binding to the origin of replication</p> Signup and view all the answers

    What is the main function of Fis in E. coli?

    <p>Participating in rRNA and tRNA transcription</p> Signup and view all the answers

    What is the consequence of HU protein deficiency in E. coli?

    <p>Severe defects in cell division, DNA folding, and DNA partitioning</p> Signup and view all the answers

    What is the pattern of Fis levels during cell growth and in response to changing environmental conditions?

    <p>Dramatic variation in response to environmental changes</p> Signup and view all the answers

    What is the structure of the bacterial nucleoid?

    <p>A coralline shape with distinct patches</p> Signup and view all the answers

    What is the role of Fis in regulating cell division?

    <p>Not directly involved in cell division</p> Signup and view all the answers

    What is the function of Fis in flagellar phase variation?

    <p>Stimulating DNA inversion</p> Signup and view all the answers

    What is the effect of Fis on fis mRNA levels during exponential growth?

    <p>Decreased fis mRNA levels</p> Signup and view all the answers

    What is the purpose of having multiple nucleoids in fast-growing bacterial cells?

    <p>To facilitate rapid cell doubling during fast growth</p> Signup and view all the answers

    During what phase of the cell cycle do duplicating nucleoids separate in bacteria?

    <p>S phase</p> Signup and view all the answers

    What is the role of proteins like ParB and SpoOJ in bacterial cell division?

    <p>They facilitate the separation of nucleoids during cell division</p> Signup and view all the answers

    What is the term used to describe the presence of multiple copies of chromosomes or nucleoids in a cell?

    <p>Multiploidy</p> Signup and view all the answers

    How do nucleoids move during replication and cell division in bacteria?

    <p>In a mitosis-like manner</p> Signup and view all the answers

    What is the region in bacteria that is directed towards the poles during cell division?

    <p>OriC region</p> Signup and view all the answers

    Which of the following bacteria lack ParB/SpoOJ homologs?

    <p>Escherichia coli and Haemophilus influenzae</p> Signup and view all the answers

    What is the term used to describe the DNA-containing region of a bacterial cell?

    <p>Nucleoid</p> Signup and view all the answers

    What is the primary function of the proteins H-NS and HU in bacteria?

    <p>To form nucleoid structures</p> Signup and view all the answers

    Which protein is also known as Rob (right origin-binding protein)?

    <p>CbpB</p> Signup and view all the answers

    What is the function of Dps in bacteria?

    <p>To protect DNA from damage during starvation</p> Signup and view all the answers

    Which protein is involved in the regulation of gene expression in response to leucine availability?

    <p>Lrp</p> Signup and view all the answers

    What is the characteristic of the nucleoid structure in Archaea?

    <p>It is composed of histone-like proteins</p> Signup and view all the answers

    What is the function of IHF in bacteria?

    <p>To integrate phage DNA into the bacterial chromosome</p> Signup and view all the answers

    What is the function of Hfq in bacteria?

    <p>To host phage Qβ</p> Signup and view all the answers

    What is the characteristic of the nucleoid structure in bacteria?

    <p>It is composed of histone-like proteins</p> Signup and view all the answers

    What is the primary function of Fis protein in E. coli?

    <p>Regulating rRNA and tRNA transcription</p> Signup and view all the answers

    What is the consequence of lack of HU protein in coli?

    <p>All of the above</p> Signup and view all the answers

    What is the role of Fis protein in flagellar phase variation?

    <p>Stimulating DNA inversion</p> Signup and view all the answers

    What is the consequence of Fis protein levels increasing during stationary phase?

    <p>Increased cell division</p> Signup and view all the answers

    What is the structure of the bacterial nucleoid?

    <p>Coralline shape</p> Signup and view all the answers

    What is the role of Fis protein in E. coli?

    <p>Participating in DNA replication</p> Signup and view all the answers

    What is the effect of Fis protein on cellular processes during exponential growth?

    <p>Fis synthesis decreases</p> Signup and view all the answers

    What is the binding site of Fis protein in E. coli?

    <p>Origin of replication (oriC)</p> Signup and view all the answers

    Study Notes

    Peptidoglycans of Bacterial Cell Walls

    • Peptidoglycan is a heteropolymer of repeating units of β-1,4-N-acetylglucosamine (NAG) and N-acetyl-muramic acid (NAM).
    • Glycan linkages of peptidoglycan are uniform in all bacteria with every D-lactyl group of the NAM being peptide substituted.
    • All glycans have short tetrapeptide units terminating with D-alanine or occasionally tripeptide units lacking the terminal D-alanine.
    • L-alanine at the N-terminus can be replaced by glycine.
    • Interpeptide bridges linking peptidoglycans are of four major types.

    Cell Wall Structure

    • Cell wall profile of B. subtilis 168 shows amorphous wall fabric directly above the plasma membrane.
    • Escherichia coli has a thin peptidoglycan murein layer above the plasma membrane, overlaid by a wavy outer membrane.
    • Clostridium thermosaccharolyticum has a wall profile intermediate between gram-positive and gram-negative formats, with a peptidoglycan layer and a proteinaceous S-layer.
    • Methanococcus voltae has a thin S-layer as its sole wall layer.

    Cytoplasmic Membranes

    • Cytoplasmic membrane is a bimolecular lipid leaflet of phospholipid molecules aligned at their hydrophobic ends.
    • Polar phospholipids are hydrophilic and face the external and internal sides of the membrane.
    • Various proteins and components may be embedded in the membrane layer.
    • Cell membrane serves as a permeability barrier, preventing most solutes from entering the cytoplasm except through specific transport proteins.

    Cell Wall Polymers

    • Chemical structures of cell wall polymers include cellulose, chitin, glucan, and mannan.
    • Yeast cell walls contain 29% β-glycans, 31% mannan, 13% protein, and small percentages of lipids and other materials.

    Prokaryotic Cell Surfaces

    • Peptidoglycan is the hallmark of eubacteria, forming the major backbone of the murein sacculus of the cell wall.
    • Archaea produce a pseudomurein and an associated surface layer (S-layer) composed of protein or glycoprotein.
    • In many archaebacteria, the S-layer may represent the only surface component outside the plasma membrane.

    Surface Layers of Bacteria

    • Bacteria from all major phylogenetic groups produce a crystalline cell surface layer (S-layer) as the outermost component of the cell.
    • S-layer may be attached to the peptidoglycan-containing sacculus or the outer membrane.

    Cell Structure and Function

    • Prokaryotic cells differ from eukaryotic cells in several major ways, including the presence of a nucleus, nuclear membrane, and other structural features.
    • Lower eukaryotes (protozoa, algae, and fungi) lack some of the distinguishing features of metazoan cells, but share a similar overall plan with eukaryotic cells.
    • Recent investigations have shown that there may be a closer similarity between eukaryotes and prokaryotes than previously thought.

    The Eukaryotic Nucleus

    • Eukaryotes have a cytologically distinct nucleus, which is the organizational and regulatory center for biochemical and hereditary processes of the cell.
    • The nucleus is composed of at least two distinct layers, with pores containing tubules that transcend both membrane layers.
    • Examples of eukaryotic cells with a discrete membrane-bound nucleus include amoebae, protozoa, algae, and fungi (yeasts and molds).

    Comparison of Cell Components

    • Prokaryotes lack a nucleus, nuclear membrane, and nucleolus, but have ribosomes similar to those found in eukaryotes.
    • Eukaryotes have a nucleus, nuclear membrane, and nucleolus, and their ribosomes are larger (40S, 60S/80S) compared to prokaryotes (30S, 50S/70S).
    • Eukaryotes have mitochondria with 70S ribosomes, while prokaryotes have cell respiration in the cytoplasmic membrane.
    • Eukaryotes have endoplasmic reticulum, Golgi apparatus, and lysosomes, while prokaryotes have a simpler cytoplasmic structure.
    • The cell wall composition differs between eukaryotes (chitin, glycans) and prokaryotes (peptidoglycan).

    Bacterial Nucleoids

    • In most bacteria, the DNA-containing region of the cell is folded into a cytologically distinct region called the nucleoid, which is not bound by a nuclear membrane.
    • The nucleoid is distinct from the eukaryotic nucleus and lacks a nuclear membrane.

    Bacterial Nucleoids

    • Bacterial cells can have multiple nucleoids, which is a common occurrence in many bacterial species.
    • This multinucleate condition is thought to facilitate rapid cell doubling during fast growth.
    • Separation of the duplicating nucleoid during cell division must occur during the S phase.
    • Fluorescence microscopy studies reveal a mitosis-like movement of immunolabeled nucleoids during replication and cell division in bacteria.

    Protein Components of Chromosomal Segregation Apparatus

    • Proteins such as ParB in Caulobacter crescentus and SpoOJ in Bacillus subtilis direct the oriC region towards the poles.
    • These proteins appear to move towards the poles in a mitosis-like manner in concert with oriC.

    Nucleoid (Histone-like) Proteins in Bacteria

    • Various proteins have been identified, including:
      • CbpA (curved DNA-binding protein A)
      • CbpB (curved DNA-binding protein B)
      • DnaA (DNA-binding protein A)
      • Dps (DNA-binding protein from starved cells)
      • Fis (factor for inversion stimulation)
      • Hfq (host factor for phage Qβ)
      • H-NS (histone-like nucleoid structuring protein)
      • HU (heat-unstable nucleoid protein)
      • IciA (inhibitor of chromosome initiation A)
      • IHF (integration host factor)
      • Lrp (leucine-responsive regulatory protein)
      • StpA (suppressor of td mutant phenotype A)
      • H1 (in mutants lacking H-NS)
    • These proteins are involved in chromosomal DNA replication and cell division.

    Mitochondria

    • Mitochondria are subcellular organelles that carry out oxidative metabolism (respiration) in eukaryotic cells.

    Structure of Bacterial Nucleoids

    • The nucleoid is a Coralline shape, as observed in exponentially growing E. coli B.
    • Immunostaining of DNA in E. coli B reveals distinct nucleoids in growing cells.

    Bacterial Nucleoids

    • Bacterial nucleoids can be multiple in fast-growing cells due to multifork replication, allowing for rapid cell doubling.
    • This multinucleate condition is common in many bacterial species.
    • Separation of duplicating nucleoids during cell division occurs during the S phase.
    • Fluorescence microscopy studies reveal a mitosis-like movement of immunolabeled nucleoids during replication and cell division in bacteria.

    Nucleoid Segregation

    • Protein components of a chromosomal segregation apparatus direct the oriC region toward the poles.
    • ParB in Caulobacter crescentus and SpoOJ in Bacillus subtilis are examples of such proteins.
    • In bacteria lacking ParB/SpoOJ homologs, other systems may participate in a mitosis-like mechanism for nucleoid segregation.

    Nucleoid (Histone-like) Proteins in Bacteria

    • Various proteins have been identified as histone-like proteins in bacteria, including:
      • CbpA (curved DNA-binding protein A)
      • CbpB (curved DNA-binding protein B)
      • DnaA (DNA-binding protein A)
      • Dps (DNA-binding protein from starved cells)
      • Fis (factor for inversion stimulation)
      • Hfq (host factor for phage Qβ)
      • H-NS (histone-like nucleoid structuring protein)
      • HU (heat-unstable nucleoid protein)
      • IciA (inhibitor of chromosome initiation A)
      • IHF (integration host factor)
      • Lrp (leucine-responsive regulatory protein)
      • StpA (suppressor of td mutant phenotype A)

    Fis Protein

    • Fis is a small, basic DNA-binding protein that stimulates DNA inversion and affects flagellar phase variation in E. coli.
    • Fis is involved in rRNA and tRNA transcription and may play a major role in chromosomal DNA replication.
    • Fis levels vary dramatically during cell growth and in response to changing environmental conditions.

    Mitochondria

    • Mitochondria are subcellular organelles that carry out oxidative metabolism (respiration) in eukaryotic cells.

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    Description

    Learn about the structure and composition of peptidoglycans in bacterial cell walls, including their uniform glycan linkages and peptide substitutions.

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