Microbial Cell structure and Function
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Questions and Answers

Which of the following statements is true about microbial morphology?

  • Morphology is are genetically encoded. (correct)
  • Morphology can predict the physiology and ecology of a prokaryotic cell.
  • Morphology can't assist in the identification of cells.
  • Bacteria and Archaea always have different morphologies.

    • Which of the following is true about chemotaxis in cells?

  • Cells move in response to chemical or physical gradients (correct)
  • Cells move in response to oxygen levels
  • Cells move towards light
  • Cells move randomly in the environment

    • What is a characteristic feature of bacterial endospores?

  • They are produced by gram-negative bacteria
  • They are located in the cytoplasm of the mother cell
  • Spore structure is the only structure not killed by sterilization
  • They are resistant to heat and harsh chemicals (correct)

    • What is the function of the exosporium in a bacterial endospore?

    <p>It protects the core from chemicals and enzymes</p> Signup and view all the answers

    What is the role of small acid-soluble spore proteins (SASPs) in bacterial endospores?

    <p>They bind tightly to DNA and protect it from damage</p> Signup and view all the answers

    What happens during the activation stage of endospore reactivation?

    <p>The spore prepares for germination</p> Signup and view all the answers

    Which of the following structures allows cells to adjust their vertical position in a water column?

    <p>Gas vesicles</p> Signup and view all the answers

    What is the main function of bacterial capsules and slime layers?

    <p>Function in attachment, immune invasion, and protection from dehydration</p> Signup and view all the answers

    What is the main function of fimbriae and pili in prokaryotic cells?

    <p>Enable cells to stick to surfaces &amp; gene exchange by conjugation</p> Signup and view all the answers

    Which of the following flagella arrangements is characterized by a tuft (group) of flagella at one end of the cell?

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

    What is the main difference between bacterial and archaeal flagella?

    <p>Bacterial flagella are powered directly by ATP, while archaeal flagella are powered by proton motive force</p> Signup and view all the answers

    Which of the following is true about small cells?

    <p>Small cells can support a larger population than large cells</p> Signup and view all the answers

    What is the function of the cytoplasmic membrane?

    <p>The cytoplasmic membrane regulates traffic of substances into and out of the cell</p> Signup and view all the answers

    What are integral membrane proteins?

    <p>Integral membrane proteins are permanently embedded in the membrane</p> Signup and view all the answers

    What is the structure of archaeal lipids?

    <p>Archaeal lipids have hydrocarbons derived from isoprene units</p> Signup and view all the answers

    What is the function of the cell wall in bacteria?

    <p>The cell wall protects against lysis</p> Signup and view all the answers

    Why is the enzyme lysozyme important in the context of cell walls?

    <p>It breaks the glycosidic bonds between sugars with peptidoglycan</p> Signup and view all the answers

    What is the function of peptide bonds in peptidoglycan?

    <p>To confer strength in the other direction</p> Signup and view all the answers

    How do gram-negative bacteria connect glycan chains in their cell walls?

    <p>Through peptide bonds between DAP and D-alanine</p> Signup and view all the answers

    What is the main component of the outer membrane in gram-negative bacteria?

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

    What is the function of porins in gram-negative cell walls?

    <p>To function as channels for the entrance and exit of solutes</p> Signup and view all the answers

    Which of the following is true about the surface to volume ratio in small cells?

    <p>Small cells have a higher surface to volume ratio than large cells.</p> Signup and view all the answers

    Which of the following is a characteristic feature of gram-positive cell walls?

    <p>They contain up to 90% peptidoglycan.</p> Signup and view all the answers

    What is the main function of teichoic acids in gram-positive cell walls?

    <p>Covalently connect to peptidoglycan</p> Signup and view all the answers

    Which of the following is true about the cell walls of Archaea?

    <p>They do not contain peptiodglycan</p> Signup and view all the answers

    What is the function of dipicolinic acid and calcium in bacterial endospores?

    <p>They increase the resistance of the core to heat and toxic chemicals</p> Signup and view all the answers

    What is the main function of pili in prokaryotic cells?

    <p>To attach the cell to surfaces</p> Signup and view all the answers

    Which of the following is true about gliding motility in prokaryotic cells?

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

    The cytoplasmic membrane is part of all cells what is not one of its part/ functions/ characteristics.

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

    The archaea cell wall structure is slightly different than bacterial, which is not one of the differences.

    <p>Instead of fatty acids, hydrocarbons are derived from isoprene a 6 carbon-compound.</p> Signup and view all the answers

    A transport mechanism in prokaryotes that allows for solutes to directly cross cell membrance is called A . When a solute reqires engery in the form a ATP to cross the cell membrance the transport is called B . Lastly when a solute require to be chemically modified to transfer into a cell uses a c .

    Signup and view all the answers

    To get out of a gram-negative cell what layer of the cell structure must you pass and what is the difference in gram-positive cells.

    <p>Gram-negative cell structure from inside to out, is cell membrane, cell wall and outer cell member Contrast to gram-positive where the cells don't have a outer cell membrane.</p> Signup and view all the answers

    The cell wall of bacteria contains all elements but.

    <p>The cell wall creates a s-layer which is interlocking layer if protein or glycoprotein that forms a paracrystalline structure.</p> Signup and view all the answers

    The beta-1,4 glycosidic bonds connect sugars in long chains while peptide bonds connect one glycan chain to another. The use of both glycosidic bonds and peptide bonds helps with the strength and rigidity of the cell wall in bacteria.

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

    Gram- negative cells have an outer membrane that is a lipid bilayer differing from the cell membrane. The outer membrane contains phospholipids and lipopolysaccharides (LPS) which replace phospholipids in the outer half of the membrane.

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

    An LPS structure contains all but.

    <p>DAP or D-alanine which attaches to polysaccharide backbone</p> Signup and view all the answers

    The different arrangements of flagella consist of and define:

    1. Polar
    2. Lophotrichous
    3. Amphitrichous
    4. Peritrichous

    <ol> <li>Polar- flagella attached to one end of cell</li> <li>A group of flagella attached to one end of cell</li> <li>groups of flagella on both ends of cell</li> <li>located all of cell surface</li> </ol> Signup and view all the answers

    Flagella Structure consists of 1. 2. 3. and are powered by 4. in bacteria and 5. in archaea.

    Signup and view all the answers

    The different types of modaility of cells. 1. 2. 3.

    <ol> <li>swimming</li> <li>Gluiding</li> <li>Twtich</li> </ol> Signup and view all the answers

    Chemotaxis is the process in which a cell moves toward or away from a chemical present in a substance. Chemicals bind to the membrane on protein called chemoreceptors.

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

    How to measure chemotaxis. The process. (control tube, attach tube and repellent tube)

    <ol> <li>Place the control tube in the substance and see if it affects microorganisms in the solution. The change in bacteria in the tube with control substance with change due to random movement but not due to attraction or repelling.</li> <li>Added attractant in the solution with bacteria and over time the concentration in the tube will drastically increase</li> <li>Add a repellent tube to the solution and over time the bacteria concentration in the tube will be lower then in the control group.</li> </ol> Signup and view all the answers

    There are many taxes which affect the movement of a bacterial cell. Chemotaxis, phototaxis, aerotaxis, osmotaxis and hydrotaxis.

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

    The reactivation process of an endospore involves activation (preparing spore for germination), germination (detection of environmental nutrients) and outgrowth (exit spore coat and return to vegetative cell).

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

    Study Notes

    Microbial Morphology

    • Microorganisms have diverse shapes and structures, which are influenced by their environment and function.

    Chemotaxis

    • Chemotaxis is the process by which cells move towards or away from a chemical substance.
    • Chemicals bind to membrane proteins called chemoreceptors.
    • Measured through a process involving a control tube, attach tube, and repellent tube.

    Bacterial Endospores

    • A characteristic feature of bacterial endospores is their resistance to environmental stressors.
    • The exosporium is the outermost layer of the endospore, providing additional protection.
    • Small acid-soluble spore proteins (SASPs) help protect the spore DNA from damage.
    • During activation, the endospore prepares for germination by rehydrating and repairing its DNA.
    • Dipicolinic acid and calcium help maintain the spore's dormancy and resistance to stress.

    Cell Motility

    • Flagella allow cells to move through their environment.
    • Flagella arrangements include polar, lophotrichous, amphitrichous, and peritrichous.
    • Flagella structure consists of a filament, hook, and basal body, powered by proton motive force in bacteria and ATP in archaea.
    • Gliding motility is a type of movement that occurs without the use of flagella.

    Cell Structure

    • The cytoplasmic membrane is responsible for regulating the flow of materials into and out of the cell.
    • Integral membrane proteins are embedded within the phospholipid bilayer of the cell membrane.
    • Archaeal lipids have a unique structure, with ether linkages instead of ester linkages.
    • The cell wall provides support and maintains the cell's shape.
    • Peptidoglycan, also known as murein, is the main component of bacterial cell walls.
    • Gram-negative bacteria connect glycan chains through lipid A molecules.
    • Porins are proteins that allow solutes to cross the outer membrane of gram-negative bacteria.
    • Teichoic acids are found in gram-positive cell walls and help maintain their structure.

    Transport Mechanisms

    • Passive transport allows solutes to cross the cell membrane without energy input.
    • Active transport requires energy, often in the form of ATP, to transport solutes.
    • Group translocation involves the chemical modification of a solute to facilitate transport.

    Cell Walls

    • Gram-negative cell walls have an outer membrane, whereas gram-positive cell walls do not.
    • The outer membrane of gram-negative bacteria contains lipopolysaccharides (LPS) and phospholipids.
    • LPS structures contain lipid A, core polysaccharides, and O-antigens.
    • The beta-1,4 glycosidic bonds connect sugars in long chains, while peptide bonds connect one glycan chain to another in peptidoglycan.

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    Lec 4-5 PDF - Microbial Cell Structure and Function

    Description

    Test your knowledge on the enzyme lysozyme and its role in cleaving bonds between sugars, weakening cell walls. Explore the presence of lysozyme in tears, saliva, and other body fluids. Learn about the structure of peptidoglycan and how β-1,4-glycosidic bonds and peptide bonds contribute to its rigidity and strength.

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