Microorganisms and Bacterial Morphology
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Questions and Answers

What is the main function of the glycocalyx in bacteria?

  • Energy storage
  • Reproduction
  • Protection against phagocytosis (correct)
  • Cell division

    • All bacteria reproduce through a process called binary fission.

    True

    What term is used to describe bacteria that maintain a single shape?

    Monomorphic

    The primary component of the bacterial cell wall is ________.

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

    Match the types of bacterial morphology with their descriptions:

    <p>Cocci = Spherical-shaped bacteria Bacilli = Rod-shaped bacteria Spirilla = Cork-screw shaped bacteria Vibrio = Curved rod-shaped bacteria</p> Signup and view all the answers

    Which of the following describes a slime layer of glycocalyx?

    <p>Unorganized and loosely attached</p> Signup and view all the answers

    All bacteria are unicellular organisms.

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

    What are the two main types of glycocalyx found in bacteria?

    <p>Slime layer and capsule</p> Signup and view all the answers

    What is the primary function of teichoic acids in Gram-positive bacteria?

    <p>Cation movement and cell growth</p> Signup and view all the answers

    Gram-negative bacteria have a thicker layer of peptidoglycan than Gram-positive bacteria.

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

    What are the two monosaccharides that make up the disaccharide portion of peptidoglycan?

    <p>N-acetylglucosamine and N-acetylmuramic acid</p> Signup and view all the answers

    Lipid A is a component of the ________ in Gram-negative bacteria and acts as an endotoxin when released.

    <p>lipopolysaccharide (LPS)</p> Signup and view all the answers

    Which enzymes are involved in the assembly of peptidoglycan on the outside of the plasma membrane?

    <p>Transglycosylases and transpeptidases</p> Signup and view all the answers

    The periplasm of Gram-negative bacteria is a viscous fluid that contains enzymes and transport proteins.

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

    Match the following components with their descriptions:

    <p>Lipid A = Functions as an endotoxin Core polysaccharide = Provides structural stability O polysaccharide = Extends outward and acts as an antigen Teichoic acids = Involved in cation movement and cell growth</p> Signup and view all the answers

    What role does the outer membrane of Gram-negative bacteria play in relation to antibiotics?

    <p>It provides a barrier to certain antibiotics and digestive enzymes.</p> Signup and view all the answers

    What role does the 0 polysaccharide play in bacteria?

    <p>It functions as an antigen.</p> Signup and view all the answers

    The cell wall of bacteria helps prevent their rupture when water pressure is greater outside than inside the cell.

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

    What are protoplasts and how do they differ from spheroplasts in terms of cell wall?

    <p>Protoplasts have their cell wall entirely removed, while spheroplasts have their cell wall only partially removed.</p> Signup and view all the answers

    The plasma membrane is described by the ______ model, which emphasizes its fluid and mosaic arrangement.

    <p>fluid mosaic</p> Signup and view all the answers

    Which of the following is not a function of the bacterial cell wall?

    <p>Metabolizing nutrients</p> Signup and view all the answers

    Match the following bacterial components with their main functions:

    <p>Cell wall = Prevents rupture of bacteria Plasma membrane = Selective barrier for material exchange Peptidoglycan = Provides structural support Lysozyme = Catalyzes hydrolysis of peptidoglycan</p> Signup and view all the answers

    Antibiotics primarily target the outer membrane of gram-negative bacteria.

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

    What is the role of enzymes associated with the plasma membrane?

    <p>They facilitate a variety of metabolic reactions and the breakdown of nutrients.</p> Signup and view all the answers

    Study Notes

    Microorganisms

    • Are microscopic organisms that can be single-celled (unicellular), a cluster of cells, or acellular (no cells).
    • Viruses require a host cell to survive and reproduce

    Cell morphology of bacteria

    • Cocci are spherical bacteria.
      • They can appear as singular, in pairs (diplococci), chains (streptococci), clusters (staphylococci), groups of four (tetrads), or groups of eight (octads).
    • Bacilli are rod-shaped bacteria.
      • They can appear short, long, thick, thin, pointed, curved, or have blunt ends.
      • They can be found in pairs, chains, long filaments, or branched.
      • Some rods are short in length, called cocobacilli.
    • Spiral, curved bacteria include vibrio (curved), spirilla (helical), and spirochete (spiral-shaped).
      • Spiral bacteria usually appear individually, but some species form pairs.
    • Bacteria can be monomorphic (single shape) or pleomorphic (many shapes).

    Prokaryotic cell structure

    • All bacteria are prokaryotes.
    • They are 10 times smaller than eukaryotic cells.
    • Prokaryotes reproduce using binary fission.
    • The cytoplasm of prokaryotes contains a chromosome, ribosomes, and other cytoplasmic particles.
    • The cytoplasm is surrounded by a cell wall and sometimes a capsule or slime layer.

    Glycocalyx

    • Is a viscous, slimy, gelatinous substance composed of polysaccharide, polypeptide, or both.
    • It is produced by the cell membrane and secreted outside of the cell wall.
    • There are two types:
      • Slime layer: unorganized and loosely attached to the cell wall.
        • Enables bacteria to glide on solid surfaces.
        • Mostly composed of exopolysaccharides, glycoproteins, and glycolipids.
      • Capsule: organized and firmly attached to the cell wall.
        • Usually consists of polysaccharide, which may be combined with lipids and proteins.
        • Protects bacteria from being phagocytosed by white blood cells.

    Peptidoglycan

    • Is a unique macromolecule found in bacterial cell walls.
    • Provides strength and rigidity to the cell wall.
    • Consists of a disaccharide (NAM and NAG) and a tetrapeptide.
    • The assembly of peptidoglycan on the outside of the plasma membrane is mediated by periplasmic enzymes, including transglycosylases, transpeptidases, and carboxypeptidases.

    Gram positive cell wall

    • Consists of many layers of peptidoglycan, forming a thick, rigid structure.
    • Contains teichoic acids, linear polymers of polyglycerol or polyribitol substituted with phosphates and a few amino acids and sugars.
    • Teichoic acids and lipoteichoic acids are negatively charged.
    • Functions of teichoic acids:
      • Facilitates cation movement
      • Aids in cell growth
      • Serves as wall antigenic specific

    Gram negative cell wall

    • Consists of one or a very few layers of peptidoglycan and an outer membrane.
    • The peptidoglycan is bonded to lipoproteins in the outer membrane.
    • The periplasm, a gel-like fluid, is located between the outer membrane and the plasma membrane.
      • Contains degradative enzymes and transport proteins.
    • The outer membrane consists of lipopolysaccharide (LPS), lipoproteins, and phospholipids.
    • Functions of the outer membrane:
      • Evade phagocytosis and immune response
      • Provide a barrier to certain antibiotics and digestive enzymes
      • Porins allow the passage of nucleotides, disaccharides, peptides, amino acids, vitamin B12, and iron.
      • LPS is composed of Lipid A (endotoxin), core polysaccharide (stability), and O polysaccharide (antigen).

    Lipopolysaccharide (LPS)

    • Lipid A is the lipid portion of the LPS and is embedded in the top layer of the outer membrane.
    • When gram-negative bacteria die, they release lipid A, which functions as an endotoxin.
    • Lipid A is responsible for symptoms associated with gram-negative infections like fever, vasodilation, shock, and blood clotting.
    • The core polysaccharide attaches to lipid A and contains unusual sugars.
      • Provides structural stability.
    • The O-polysaccharide extends outward from the core polysaccharide and is composed of sugar molecules.
      • Functions as an antigen and is useful for distinguishing species of gram-negative bacteria.

    Cell wall function

    • Prevents bacterial cells from rupturing when internal water pressure is higher than external pressure.
    • Helps maintain the shape of the bacterium and serves as an anchor for flagella.
    • Contributes to the ability of some species to cause disease.
    • Is the site of action for some antibiotics.

    Cell wall damage

    • Lysozyme is an enzyme that hydrolyzes the bonds between sugars in peptidoglycan.
      • Primarily active against gram-positive bacteria.
    • Protoplasts (gram-positive) have their cell wall completely removed.
    • Spheroplasts (gram-negative) have their cell wall partially removed.

    Cell membrane (plasma membrane)

    • Consists of proteins (peripheral and integral) and phospholipids, arranged in a fluid mosaic model.
    • Flexible and thin.
    • Functions:
      • It is a selective barrier for materials entering and exiting the cell (passive and active movement).
      • Many enzymes are attached to the membrane, and metabolic reactions occur there.
      • Involved in the breakdown of nutrients and the production of energy.

    Cytoplasm

    • The semi-liquid cytoplasm of prokaryotes consists of water, enzymes, dissolved oxygen, waste products, essential nutrients, proteins, carbohydrates, and lipids.
    • It houses all the materials needed for metabolic functions.

    Chromatophores

    • In some bacteria, pigments and enzymes involved in photosynthesis are found in infoldings of the plasma membrane that extend into the cytoplasm.

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    Introduction to Microorganisms Lecture 2 PDF

    Description

    Explore the fascinating world of microorganisms, focusing on their structure and classification. This quiz covers different shapes of bacteria, including cocci, bacilli, and spiral types, as well as the basic features of prokaryotic cells. Test your knowledge and understanding of these essential life forms.

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