Microbiology Chapter Three Exam Practice
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Questions and Answers

What is the primary staining step in the Gram stain procedure?

  • Malachite Green
  • Crystal Violet (correct)
  • Safranin
  • Red Carbolfuchsin

    • What color do Gram-positive cells typically appear as under the microscope?

  • Blue/Purple (correct)
  • Pink/Red
  • Green
  • Yellow

    • What is the purpose of using Acid-Fast stains in microbiology?

  • To differentiate between Gram-positive and Gram-negative bacteria
  • To detect organisms with waxy coats like Mycobacterium (correct)
  • To highlight flagella structure
  • To stain endospores

    • What is the approximate size of a bacterial cell?

    <p>3 μm</p> Signup and view all the answers

    Which part of the microscope controls the amount of light that enters the objective lens?

    <p>Iris diaphragm lever</p> Signup and view all the answers

    What is the purpose of using stains in microscopy?

    <p>To add contrast to the specimen</p> Signup and view all the answers

    Which type of cell has ribosomes that are 80S?

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

    Which bacterial type is unaffected by penicillin and lysozyme due to the lack of a cell wall?

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

    Which bacterial type stains purple/violet due to its thick peptidoglycan layer?

    <p>Gram Positive</p> Signup and view all the answers

    What is the main function of the outer membrane in Gram-negative bacteria?

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

    A bacterial cell is typically larger than 3 micrometers in size.

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

    The compound light microscope uses only one lens for magnification.

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

    Capsules of bacteria do not stain because they have a strong positive charge.

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

    Crystal violet forms crystals outside the cell in Gram positive bacteria.

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

    Acid-Fast stains are used to detect organisms that easily take up stains.

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

    Capsule staining involves darkening the capsule area to make it less visible.

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

    Eukaryotic cells are typically smaller in size compared to prokaryotic cells.

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

    Gram-positive bacteria have a thin peptidoglycan layer protected by an outer membrane.

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

    Mycoplasma pneumoniae has a cell wall composed of peptidoglycan.

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

    Penicillin is an antibiotic that targets peptidoglycan synthesis in bacterial cell walls.

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

    What is the function of the immersion oil in a microscope?

    <p>To improve resolution</p> Signup and view all the answers

    Explain the purpose of using stains in microscopy and provide an example of how stains work.

    <p>Stains are used to increase contrast and make certain cell structures more visible. Basic dyes are positively charged and are used with negatively charged bacteria to enhance visibility.</p> Signup and view all the answers

    Why do bacterial capsules not stain during capsule staining procedures?

    <p>Capsules do not stain because they are non-ionic.</p> Signup and view all the answers

    Explain the difference between Gram positive and Gram negative cells in terms of the cell wall composition and staining characteristics.

    <p>Gram positive cells have lots of peptidoglycan in the cell wall, retain crystal violet stain, and appear purple/blue. Gram negative cells have a protective outer membrane, less peptidoglycan, wash off crystal violet easily, and appear pink/red after safranin staining.</p> Signup and view all the answers

    Describe the procedure for Acid-Fast staining and explain why it is used in microbiology.

    <p>The procedure involves using red carbolfuchsin as the primary stain, decolorizing with acid alcohol, and counterstaining with methylene blue. It is used to detect bacteria with waxy coats, like Mycobacterium leprae and M.tuberculosis, that are resistant to standard staining methods.</p> Signup and view all the answers

    What is the purpose of Endospore staining? Describe the staining procedure used for Endospores.

    <p>Endospore staining is used to visualize bacterial endospores, which are tough and resistant structures. The staining procedure involves using Malachite Green as the primary stain with steam, followed by a Safranin counterstain.</p> Signup and view all the answers

    Which type of cell has a true nucleus?

    <p>B. Eukaryotic</p> Signup and view all the answers

    Which bacterial organism is considered Prokaryotic?

    <p>A. Prokaryotic</p> Signup and view all the answers

    What is the specific target of the antibiotic Penicillin?

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

    Which of the following types of bacteria have LPS endotoxin?

    <p>B. Gram negative</p> Signup and view all the answers

    The total magnification in a microscope is the product of the magnifying power of the ocular lens and the ______ lens.

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

    Immersion oil has the same refractive index as ______.

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

    Stains in microbiology are used to provide ______ to specimens.

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

    Gram Stain Procedure was developed by __________.

    <p>Hans Christian Gram</p> Signup and view all the answers

    The Gram Stain procedure uses Crystal Violet as the primary _________.

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

    Gram Negative cells generally appear pink/red after counterstaining with _________.

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

    The staining agent adheres to and coats the otherwise thin flagella, making them visible with the light microscope. This process is known as Flagella ______.

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

    Bacteria reproduce through ______ fission.

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

    Eukaryotic cells possess a true ______ containing many linear chromosomes.

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

    Bacterial Cell Wall is composed of ______.

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

    Match the following units of measurement with their corresponding values in powers of 10:

    <p>deci = Tenth 10^-1 milli = Thousandth 10^-3 micro = Millionth 10^-6 nano = Billionth 10^-9</p> Signup and view all the answers

    Match the following microscope components with their functions:

    <p>Ocular Lens = Magnifies the image Condenser Lens = Focuses the light Objective Lens = Provides different magnifications Iris diaphragm lever = Controls the amount of light that enters the objective lens</p> Signup and view all the answers

    Match the following staining concepts with their descriptions:

    <p>Basic Dyes = (+) charged dyes used with bacteria which are slightly negative Acidic Dyes = (-) charged dyes used for capsules that don't stain (non-ionic) Background Stains = Used to see capsules in microscopy Capsule Staining = Involves darkening the capsule area to make it less visible</p> Signup and view all the answers

    Match the cell type with the correct description:

    <p>Prokaryotic = Very small cell size, simple structure, unicellular, 70S ribosomes Eukaryotic = Larger cell size, complex structure, unicellular or multicellular, 80S ribosomes</p> Signup and view all the answers

    Match the bacterial arrangement with the correct bacteria:

    <p>Diplococcus = Neisseria gonorrhoeae Streptococcus = Streptococcus pyogenes Staphylococcus = Staphylococcus aureus</p> Signup and view all the answers

    Match the staining technique with its specific characteristic:

    <p>Gram Stain = Used to separate bacteria into Gram-positive and Gram-negative groups Acid-Fast Stain = Utilized to detect organisms resistant to staining, like Mycobacterium Capsule Stain = Involves darkening the background to highlight the capsule area Endospore Stain = Specifically targets staining endospores, dormant cells with resistance</p> Signup and view all the answers

    Match the bacterial type with the correct cell wall description:

    <p>Gram Positive = Stains purple/violet, many layers of peptidoglycan and teichoic acid Gram Negative = Stains red/pink, thin peptidoglycan layer protected by outer membrane with LPS</p> Signup and view all the answers

    Match the antibiotic with its specific target in bacterial cells:

    <p>Lysozyme = Cuts sugar bars in peptidoglycan Penicillin = Blocks peptidoglycan-making enzyme (PBP enzyme)</p> Signup and view all the answers

    Match the bacteria classification with its characteristic under the microscope:

    <p>Gram Positive = Appears purple/blue under the microscope Gram Negative = Generally appears pink/red after counterstaining Acid-Fast Positive = Red stained cells under the microscope Acid-Fast Negative = Blue stained cells under the microscope</p> Signup and view all the answers

    Match the primary stain with the corresponding staining procedure:

    <p>Crystal Violet = Primary stain in Gram Stain procedure Red Carbolfuchsin = Primary stain in Acid-Fast Stain procedure Malachite Green = Primary stain in Endospore Stain procedure Methylene Blue = Counterstain used in Capsule Staining procedure</p> Signup and view all the answers

    Which type of bacteria is unaffected by penicillin and lysozyme due to the lack of a cell wall?

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

    What is the main function of teichoic acid in bacterial cell walls?

    <p>Prevents cell lysis</p> Signup and view all the answers

    Which enzyme specifically targets the peptidoglycan-making enzyme in bacterial cells?

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

    Which bacterial arrangement is characteristic of Staphylococcus aureus?

    <p>Staphylo-</p> Signup and view all the answers

    Which part of the bacterial cell contains one circular chromosome and possible extra DNA known as plasmids?

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

    Flagella staining involves making the flagella invisible under the light microscope.

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

    Eukaryotic cells typically reproduce through binary fission.

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

    Prokaryotic cells lack membrane-enclosed organelles.

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

    Gram-positive bacteria have a thin peptidoglycan layer protected by lipopolysaccharides (LPS).

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

    Eukaryotic cells are generally smaller in size compared to prokaryotic cells.

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

    Which type of bacteria lacks a cell wall?

    <p>Mycoplasma pneumoniae</p> Signup and view all the answers

    What is the specific target of the antibiotic Penicillin?

    <p>Peptidoglycan-making enzyme</p> Signup and view all the answers

    What is the main function of teichoic acid in bacterial cell walls?

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

    What process do most prokaryotes/bacteria use for division?

    <p>Binary fission</p> Signup and view all the answers

    Which staining technique makes flagella visible under the light microscope?

    <p>Flagella staining</p> Signup and view all the answers

    Which cell type has a ______ nucleus? A.Prokaryotic B.Eukaryotic C.Both D.Neither

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

    Which cell type has ______? A.Prokaryotes B.Eukaryotes C.Both D.Neither

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

    Which cell type has ______? A.Prokaryotes B.Eukaryotes C.Both D.Neither

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

    The bacterial organism that you are writing your report on is considered _____. A.Prokaryotic B.Eukaryotic C.Both D.Neither

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

    Which of the following types of bacteria lacks a cell wall? A.Gram Positive B.Gram Negative C.Both D.______ of the above

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

    Match the primary characteristics of Prokaryotic Cells and Eukaryotic Cells:

    <p>Very small cell size = Larger cell size Simple structure = Complex structure Reproduce through binary fission = Reproduce through mitosis and cytokinesis Contains one circular chromosome and possible extra DNA known as plasmids = True nucleus containing many linear chromosomes</p> Signup and view all the answers

    Match the bacterial cell types with their ribosome composition:

    <p>Prokaryotic Cells (Prokaryotes) = 80S Ribosomes Eukaryotic Cells (Eukaryotes) = 70S Ribosomes</p> Signup and view all the answers

    Match the bacterial cell types with their mode of reproduction:

    <p>Prokaryotic Cells (Prokaryotes) = Mitosis and cytokinesis Eukaryotic Cells (Eukaryotes) = Binary fission</p> Signup and view all the answers

    Match the bacterial arrangements with their corresponding bacteria:

    <p>Diplococcus = Neisseria gonorrhoeae, N.meningitidis Streptococcus = Streptococcus pyogenes Staphylococcus = Staphylococcus aureus Streptobacillus = Strepto-</p> Signup and view all the answers

    Match the components of the bacterial cell envelope with their descriptions:

    <p>Cytoplasmic membrane = Composed of peptidoglycan, stains purple/violet in Gram stain Bacterial Cell Wall = Composed of lipopolysaccharides, protects against lysozyme</p> Signup and view all the answers

    Study Notes

    Microscope and Measurement

    • The microscope includes compound light, electron microscope, and others like atomic-force microscopy.
    • The compound light microscope uses many lenses: ocular 10x, condenser (condenses light), objectives (scanning 4x, low 10x, high 40x, oil 100x).
    • The total magnification is the product of the magnifying power of the ocular lens and the objective lens.
    • The iris diaphragm lever controls the amount of light that enters the objective lens.
    • The light source rheostat controls the brightness of the light.

    Measurement Units

    • deci: Tenth (10^-1)
    • centi: Hundredth (10^-2)
    • milli: Thousandth (10^-3)
    • micro: Millionth (10^-6)
    • nano: Billionth (10^-9)
    • pico: Trillionth (10^-12)
    • The approximate size of a bacterial cell is 3 μm (micrometers).

    Stains

    • Stains contain both (+) and (-) ions but are slightly charged.
    • Basic Dyes are (+) and Acidic Dyes are (-).
    • Stains are used to create contrast for better visibility.
    • Background stains are used to see capsules, which don't stain (non-ionic).

    Gram Stain

    • Gram stain is a differential stain that separates bacteria into two major groups: Gram-positive and Gram-negative.
    • Gram-positive bacteria:
      • Contain lots of peptidoglycan in the cell wall.
      • Crystal violet forms crystals within the cell.
      • Retain the crystal violet stain after decolorization.
      • Appear purple/blue under the microscope.
      • Example: Staphylococcus aureus.
    • Gram-negative bacteria:
      • Possess a protective outer membrane.
      • Contain less peptidoglycan in the cell wall.
      • Crystal violet washes off more easily during decolorization.
      • Appear pink/red after counterstaining with safranin.
      • Example: Escherichia coli.

    Other Stains

    • Acid-Fast Stain: Used to detect organisms that do not easily take up stains, particularly members of the genus Mycobacterium.
    • Endospore Stain: Used to stain endospores, a type of dormant cell that does not readily take up the stains.
    • Flagella Staining: Used to highlight the structure of flagella.
    • Capsule Staining: Used to create a clear halo around capsule bacteria or fungal cells.### Gram Stain Procedure
    • The Gram stain procedure involves crystal violet as the primary stain, iodine as a mordant, decolorization with alcohol or alcohol acetone, and counterstaining with safranin.
    • The Gram stain differentiates bacteria into two groups: Gram-positive and Gram-negative.

    Gram-Positive Bacteria

    • Gram-positive bacteria have a thick peptidoglycan layer in their cell walls.
    • Crystal violet forms crystals within the cell and is retained during decolorization, resulting in a purple/blue appearance under the microscope.
    • Examples of Gram-positive bacteria include Staphylococcus aureus.

    Gram-Negative Bacteria

    • Gram-negative bacteria have a protective outer membrane and less peptidoglycan in their cell walls.
    • Crystal violet is washed off during decolorization, resulting in a pink/red appearance after counterstaining with safranin.
    • Examples of Gram-negative bacteria include Escherichia coli.

    Acid-Fast Stain

    • The acid-fast stain is used for bacteria with a waxy coat, such as Mycobacterium leprae and M. tuberculosis.
    • The procedure involves using red carbolfuchsin as the primary stain, 3% acid alcohol as the decolorizing agent, and methylene blue as the counterstain.
    • Acid-fast cells appear red, while non-acid-fast cells appear blue.

    Endospore Stain

    • The endospore stain is used to detect endospores, which are resistant to dye penetration.
    • The procedure involves using malachite green with steam as the primary stain, followed by safranin as the counterstain.

    Flagella Staining

    • Flagella staining involves using very thin coats of the staining solution to highlight the structure of flagella.

    Capsule Staining

    • Capsule staining involves using background staining to create a clear halo around capsule bacteria or fungal cells.

    Stain Characteristics

    • Simple stains use a basic dye to increase contrast between cells and the background.
    • Differential stains use a multistep procedure to distinguish between different groups of microorganisms.
    • Special stains use a specific procedure to stain specific cell structures.

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