Microbiology Final Exam Quiz - 2

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Microbiology Final Exam Quiz - 2 - Quiz


Take this interesting and typical quiz on microbiology and associated microscopic nonliving biological particles that interact with living things


Questions and Answers
  • 1. 

    Which is (are) true concerning the cell wall of bacteria?

    • A.

      It determines the shape of the bacteria

    • B.

      It prevents the bacteria from lysis

    • C.

      It contains peptidoglycan

    • D.

      It may be targeted by antibiotics such as penicillin

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    The cell wall of bacteria has multiple functions. It determines the shape of the bacteria, providing structural support. It also prevents the bacteria from undergoing lysis, which is the bursting of the cell due to osmotic pressure. The cell wall contains peptidoglycan, a unique molecule found in bacterial cell walls. Lastly, the cell wall can be targeted by antibiotics such as penicillin, which interfere with the synthesis of peptidoglycan, weakening the cell wall and leading to bacterial death. Therefore, all of the statements mentioned are true regarding the cell wall of bacteria.

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  • 2. 

    Microorganisms have been very helpful in research especially because

    • A.

      They have relatively simple structures

    • B.

      Most of them have short generation time allowing data collection in a short period of time

    • C.

      A large population can be kept in a small space

    • D.

      It is easy to visualize any transfer of genetic material

    • E.

      A, B and C are correct

    Correct Answer
    E. A, B and C are correct
    Explanation
    Microorganisms have been very helpful in research due to their relatively simple structures, short generation time, and the ability to maintain a large population in a small space. These characteristics make it easier to study and collect data from microorganisms in a shorter period of time. Additionally, their simple structures make it easier to visualize any transfer of genetic material, aiding in genetic research. Therefore, options A, B, and C are all correct explanations for why microorganisms are helpful in research.

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  • 3. 

    Koch's postulates for linking a specific disease with its causative agent DOES NOT include which of the folowing?

    • A.

      The specific causative agent must be found in every case of the disease

    • B.

      The disease organism must be isolated in pure culture

    • C.

      Inoculation of a sample of the culture into a healthy, susceptible animal must produce the same disease

    • D.

      Human subjects must be inoculated with the organism to assay its virulence

    • E.

      None of the above

    Correct Answer
    D. Human subjects must be inoculated with the organism to assay its virulence
    Explanation
    Koch's postulates are a set of criteria used to establish a causal relationship between a specific disease and its causative agent. These postulates include the following steps: (1) The specific causative agent must be found in every case of the disease. (2) The disease organism must be isolated in pure culture. (3) Inoculation of a sample of the culture into a healthy, susceptible animal must produce the same disease. The given answer states that human subjects must be inoculated with the organism to assay its virulence, which is not a part of Koch's postulates.

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  • 4. 

    What characteristic do bright-field microscope, dark-field microscopes and the differential interference contrast microscope have in common?

    • A.

      Visualize small molecules inside the cells

    • B.

      Observe living specimens

    • C.

      Deal with refractive index minimizing blurry images

    • D.

      Work with specimens with differentially staining it

    Correct Answer
    B. Observe living specimens
    Explanation
    Bright-field microscopes, dark-field microscopes, and the differential interference contrast microscope all have the characteristic of being able to observe living specimens. These types of microscopes are specifically designed to allow for the observation of specimens in their natural, living state, without causing harm or altering their behavior. This is a crucial feature when studying biological samples and allows for the observation of dynamic processes and interactions within living cells and organisms.

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  • 5. 

    Which combination of objective lenses and ocular (eyepieces) lenses prvides the observer the highest magnification?

    • A.

      40x objective combined with 20x ocular

    • B.

      100x objective combined with 10x ocular

    • C.

      100x objective combined with 20x ocular

    • D.

      20x ovjective combined with 20x ocular

    Correct Answer
    C. 100x objective combined with 20x ocular
    Explanation
    The combination of a 100x objective lens and a 20x ocular lens provides the highest magnification for the observer. The magnification of a microscope is calculated by multiplying the magnification of the objective lens with the magnification of the ocular lens. Therefore, 100x objective multiplied by 20x ocular gives a total magnification of 2000x, which is the highest among the given options.

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  • 6. 

    _____ refers to the ability to distinguish adjacent objects, and ____ refers to the capactiy of visualizing the object

    • A.

      Wavelength; frequency

    • B.

      Resolution; detection

    • C.

      Resolution; magnification

    • D.

      Frequency; resolution

    • E.

      Refraction; detection

    Correct Answer
    B. Resolution; detection
    Explanation
    Resolution refers to the ability to distinguish adjacent objects, while detection refers to the capacity of visualizing the object. In other words, resolution is the ability to see fine details and distinguish between closely spaced objects, while detection is the ability to perceive and identify the presence of an object.

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  • 7. 

    The function of the immersion oil when using the 100x objective is to 

    • A.

      Increase the refractive index, and increase the resolution

    • B.

      Avoid contact between the objective and the slide

    • C.

      Increase the refractive index and decrease the resolution

    • D.

      Decrease the refractive index allowing more light to reach the slide

    Correct Answer
    A. Increase the refractive index, and increase the resolution
    Explanation
    The function of the immersion oil when using the 100x objective is to increase the refractive index and increase the resolution. Immersion oil has a higher refractive index compared to air, which helps to reduce the loss of light as it passes through different media with different refractive indices. This increased refractive index improves the resolution of the microscope by reducing the diffraction of light and allowing for clearer and more detailed images to be observed.

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  • 8. 

    Stains can be used to visualize

    • A.

      Capsules

    • B.

      Endospores

    • C.

      Cell wall

    • D.

      Flagella

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    Stains can be used to visualize various components of cells, including capsules, endospores, cell walls, and flagella. By using specific stains, these structures can be highlighted and made visible under a microscope. Therefore, the correct answer is "all of the above" as stains can be used to visualize all of these components.

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  • 9. 

    Which of the following is NOT paired correctly?

    • A.

      Fluid mosaic model; currently accepted model of cell membranes

    • B.

      Cell envelope; association of plasma membrane and cell wall

    • C.

      Nucleoid; irregular shaped region where genetic material is found

    • D.

      Spirillum; a rigid spiral-shaped bacterial or archaeal cell

    Correct Answer
    B. Cell envelope; association of plasma membrane and cell wall
    Explanation
    The correct answer is "cell envelope; association of plasma membrane and cell wall." This is because the cell envelope actually consists of the plasma membrane and all of its associated structures, including the cell wall. It is not just the association between the plasma membrane and cell wall.

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  • 10. 

    What is the relevance of surface area-to-volume ratio?

    • A.

      None, there is no correlation between surface area and cell volume

    • B.

      When surface area-to-volume ratio decreases, nutrient uptake becomes more efficient

    • C.

      When surface area-to-volume ratio increases, nutrient uptake becomes more efficient

    • D.

      When the surface area-to-volume ratio increases, cells can easily get desiccated

    Correct Answer
    C. When surface area-to-volume ratio increases, nutrient uptake becomes more efficient
    Explanation
    The surface area-to-volume ratio is important because it determines the efficiency of nutrient uptake in cells. When the ratio increases, it means that the surface area of the cell is larger relative to its volume. This allows for more surface area available for nutrient absorption, leading to more efficient nutrient uptake. Therefore, the correct answer is that when surface area-to-volume ratio increases, nutrient uptake becomes more efficient.

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  • 11. 

    Some bacteria have flagella all over their cell. this kind of arrangement is called

    • A.

      Monotrichous

    • B.

      Peritrichous

    • C.

      Lophotrichous

    • D.

      Halotrichous

    • E.

      Amphitrichous

    Correct Answer
    B. Peritrichous
    Explanation
    Peritrichous is the correct answer because this term describes the arrangement of flagella all over the cell surface. It means that the bacteria have multiple flagella distributed around the cell, allowing for movement in various directions.

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  • 12. 

    Bacterial plasma membrane is embedded with several proteins that perform functions such as ___ and ___. the rigidity of the membrane is maintained by the presence of ___.

    • A.

      Structural support; secretin of virulence factor; hopanoids

    • B.

      Ion transport osmotic maintenance; sterols

    • C.

      Structural support; secretion of virulence factor; sterols

    • D.

      Fluidity; virulence; phospholipids

    • E.

      Ion transport; osmotic maintenance; phospholipids

    Correct Answer
    A. Structural support; secretin of virulence factor; hopanoids
    Explanation
    The bacterial plasma membrane is embedded with several proteins that perform functions such as providing structural support and secreting virulence factors. The rigidity of the membrane is maintained by the presence of hopanoids.

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  • 13. 

    Archaeal cell wall is formed by a polymer made of NAT and NAG referred to as

    • A.

      Murein

    • B.

      Pseudopeptidoglycan

    • C.

      Acid-fast

    • D.

      Lipopolysacharide

    • E.

      None of the above are correct

    Correct Answer
    B. Pseudopeptidoglycan
    Explanation
    The correct answer is pseudopeptidoglycan. Archaeal cell walls are composed of a polymer made of N-acetylglucosamine (NAG) and N-acetyltalosaminuronic acid (NAT), which is referred to as pseudopeptidoglycan. This structure is similar to bacterial peptidoglycan but has some key differences. Pseudopeptidoglycan provides strength and stability to the archaeal cell wall, allowing it to withstand harsh environmental conditions.

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  • 14. 

    One of the answers below can NOT be counted as Pasteur's contribution to microbiology as a science

    • A.

      The development of the pasteurization process

    • B.

      Development of vaccine against smallpox

    • C.

      The description of a protozoan as the infection agent in silkworms causing pebrine disease

    • D.

      The description of the fermentation process and its results when carried out by yeast or bacteria

    Correct Answer
    B. Development of vaccine against smallpox
    Explanation
    The development of a vaccine against smallpox is not considered Pasteur's contribution to microbiology as a science because it was actually Edward Jenner who first developed the smallpox vaccine. Pasteur's contributions to microbiology primarily revolve around the development of the pasteurization process, the description of a protozoan as the infection agent in silkworms causing pebrine disease, and the description of the fermentation process and its results when carried out by yeast or bacteria.

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  • 15. 

    Which of the following is NOT a characteristic of electron microscopy?

    • A.

      Electron microscope images allow us to describe and visualize living specimens

    • B.

      The transmission electron microscope used magnetic lenses to form an image from electrons that have passed through a very thin section of a specimen

    • C.

      The scanning electron microscope is used to examine the surfaces of microorganismsmin great detail

    • D.

      Electron microscopes are able to detect and resolve particles as small as proteins

    Correct Answer
    A. Electron microscope images allow us to describe and visualize living specimens
  • 16. 

    Prokaryotic cells are characterized by the 

    • A.

      Absence of ribosomes

    • B.

      Absence of DNA

    • C.

      Absence of a membrane-limited nucleus

    • D.

      Absence of membranous organelles

    • E.

      C & D are correct

    Correct Answer
    E. C & D are correct
    Explanation
    Prokaryotic cells are characterized by the absence of a membrane-limited nucleus and the absence of membranous organelles. Unlike eukaryotic cells, prokaryotic cells do not have a defined nucleus enclosed within a membrane. They also lack membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus. However, prokaryotic cells do have ribosomes, which are responsible for protein synthesis. Therefore, the correct answer is C & D, as prokaryotic cells lack a membrane-limited nucleus and membranous organelles.

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  • 17. 

    Analyzes of ribosomal RNA done in the 1970's by Carl Woes, showed major differences betwen __ and ___; both prokaryotic organisms belonging to the same kingdom

    • A.

      Bacteria and protists

    • B.

      Protists and archaea

    • C.

      Protist and viruses

    • D.

      Bacteria and archaea

    • E.

      Viruses and viroids

    Correct Answer
    D. Bacteria and archaea
    Explanation
    The correct answer is bacteria and archaea. The analysis of ribosomal RNA conducted by Carl Woes in the 1970s revealed significant differences between these two prokaryotic organisms that belong to the same kingdom. This suggests that bacteria and archaea are distinct and separate groups within the microbial world.

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  • 18. 

    The __ and ___ vwere critical in the development of microbiology

    • A.

      Development of Bunsen burners; plates

    • B.

      Development of microscopes; development of techniques for isolating microbes

    • C.

      Establishment of Koch's postulates; plates

    • D.

      Invention of plates; loops

    Correct Answer
    B. Development of microscopes; development of techniques for isolating microbes
    Explanation
    The development of microscopes was critical in the field of microbiology as it allowed scientists to observe and study microorganisms in detail for the first time. Microscopes enabled researchers to discover the existence of bacteria, viruses, and other microscopic organisms, leading to significant advancements in understanding the microbial world. Additionally, the development of techniques for isolating microbes was crucial in microbiology as it allowed scientists to grow and study microorganisms in pure cultures, enabling further research and the identification of specific microbial species.

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  • 19. 

    What kind of information is provided by isolating microorganisms from their natural environment and culturing them in the laboratory

    • A.

      Generation time

    • B.

      Nutrient requirement

    • C.

      Temperature requirement

    • D.

      Cellular shape

    • E.

      A, B & C are correct

    Correct Answer
    E. A, B & C are correct
    Explanation
    Isolating microorganisms from their natural environment and culturing them in the laboratory can provide information about their generation time, nutrient requirement, and temperature requirement. By studying microorganisms in a controlled environment, scientists can observe how quickly they reproduce, what specific nutrients they need to survive and grow, and the temperature range in which they thrive. This information is important for understanding the biology and ecology of microorganisms and can also have practical applications in fields such as medicine, agriculture, and environmental science.

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  • 20. 

    Light of ___ wavelength typically will result in ___ resolution

    • A.

      Longer; better

    • B.

      Longer; poor

    • C.

      Medium; better

    • D.

      Shorter;better

    • E.

      Shorter;worse

    Correct Answer
    D. Shorter;better
    Explanation
    Light of shorter wavelength typically will result in better resolution. This is because shorter wavelengths allow for smaller details to be resolved and distinguishable. As the wavelength of light decreases, the ability to distinguish between two closely spaced objects improves, resulting in better resolution. Therefore, light of shorter wavelength is preferred for achieving higher resolution in various imaging techniques such as microscopy or photography.

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  • 21. 

    Why was the belief of spontaneous generation an obstacle to the development of microbiology as a science

    • A.

      It would be impossible to have a sterile medium

    • B.

      It would be difficult to link microorganism to certain diseases

    • C.

      It would be hard to isolate cultures

    • D.

      All of the above

    Correct Answer
    D. All of the above
    Explanation
    The belief of spontaneous generation hindered the development of microbiology as a science because it implied that microorganisms could arise spontaneously from non-living matter, making it impossible to have a sterile medium for studying them. This belief also made it difficult to establish a link between microorganisms and certain diseases, as the idea of spontaneous generation suggested that diseases could arise without the presence of microorganisms. Additionally, if microorganisms were thought to spontaneously generate, it would be challenging to isolate and study them in pure cultures, as their origin would be uncertain.

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  • 22. 

    In some Archaea, the double layer of phospholipid membane is replaced by a ___, making the membrane____ and resistant to harch environments

    • A.

      Monolayer, more rigid

    • B.

      Triple layer, more rigid

    • C.

      Outer membrane, more rigid

    • D.

      Monolayer, less rigid

    • E.

      Triple layer, less rigid

    Correct Answer
    A. Monolayer, more rigid
    Explanation
    In some Archaea, the double layer of phospholipid membrane is replaced by a monolayer, making the membrane more rigid and resistant to harsh environments. This is because the monolayer structure provides a stronger and more stable barrier, allowing the Archaea to survive in extreme conditions. The absence of a second layer reduces the flexibility of the membrane, making it less prone to deformation and damage.

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  • 23. 

    Which of the following statements about endospores is NOT correct

    • A.

      They are resistant to heat, chemicals, radiation a desiccation

    • B.

      Endospore formation is triggered by lack of nutrients

    • C.

      Most bacteria and archaea are able to form endospores

    • D.

      Resistance to physical factors is due to high amount of dipocolinic acid and calcium

    Correct Answer
    C. Most bacteria and archaea are able to form endospores
    Explanation
    Most bacteria and archaea are able to form endospores is not correct. Only certain bacteria, such as Bacillus and Clostridium species, have the ability to form endospores.

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  • 24. 

    An evidence of early microbial life on Earth can be revealed in

    • A.

      Ribosomal RNA

    • B.

      Stromatolites

    • C.

      Microbial evolution

    • D.

      Cellular metabolism

    • E.

      Probionts

    Correct Answer
    B. Stromatolites
    Explanation
    Stromatolites are rock-like structures formed by the trapping and binding of sediment by microbial communities, specifically cyanobacteria. These structures can be found in ancient rock formations and provide evidence of early microbial life on Earth. The presence of stromatolites suggests that microbial communities were present and actively involved in the formation of these structures, indicating the existence of early microbial life on Earth. Therefore, stromatolites serve as an important piece of evidence for the existence and evolution of microbial life on our planet.

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  • 25. 

    Bacteriological media that are composed of ingredients whose exact chemical composition are known are called

    • A.

      Designated

    • B.

      Exact

    • C.

      Defined

    • D.

      Selective

    • E.

      Aesthetic

    Correct Answer
    C. Defined
    Explanation
    Bacteriological media that are composed of ingredients whose exact chemical composition are known are called "defined". This means that all the components and their quantities in the media are precisely known. This is important in scientific research and experimentation, as it allows for consistency and reproducibility of results. By using defined media, researchers can control and manipulate the growth conditions of bacteria more accurately, leading to more reliable and valid experiments.

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  • 26. 

    The endosymbiotic hypothesis 

    • A.

      Is generally accepted as origin of mitochondria and chloroplasts in eukaryotic cells

    • B.

      States that formation of biofilm is due to symbiosis

    • C.

      Is largely accepted for explaining microbial diversity

    • D.

      Does not involve prokaryotic organisms therefore should not be discussed here

    Correct Answer
    A. Is generally accepted as origin of mitochondria and chloroplasts in eukaryotic cells
    Explanation
    The endosymbiotic hypothesis is generally accepted as the origin of mitochondria and chloroplasts in eukaryotic cells. This hypothesis suggests that mitochondria and chloroplasts were once free-living prokaryotic organisms that were engulfed by a host cell. Over time, a symbiotic relationship developed between the host cell and the engulfed organisms, leading to the integration of their genetic material and the formation of organelles within the host cell. This theory is widely accepted and supported by evidence such as the presence of DNA and ribosomes within mitochondria and chloroplasts, which resemble those found in prokaryotes.

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  • 27. 

    Bacterial flagellar motion is 

    • A.

      Rotational

    • B.

      Whiplash

    • C.

      Ondulatory

    Correct Answer
    A. Rotational
    Explanation
    The correct answer is rotational because bacterial flagellar motion involves a rotating movement. The flagella of bacteria act like propellers, spinning in a circular motion to propel the bacteria forward. This rotational motion allows the bacteria to move efficiently through their environment.

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  • 28. 

    The movement of a cell towards a chemical or away from a chemical is called

    • A.

      Chemosmosis

    • B.

      Chemoattraction

    • C.

      Chemosynthetic

    • D.

      Chemotaxis

    • E.

      Chemosignaling

    Correct Answer
    D. Chemotaxis
    Explanation
    Chemoattraction refers to the movement of a cell towards a chemical, while chemorepulsion refers to the movement away from a chemical. Chemosynthesis is the process by which organisms use chemicals to produce energy, and chemosignaling is the communication between cells using chemical signals. Chemosmosis is not a term used to describe the movement of a cell towards or away from a chemical. Therefore, the correct answer is chemotaxis.

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  • 29. 

    Which of the following is NOT matched correctly

    • A.

      Lithotrophs; organisms that use inorganic compounds as its electron source

    • B.

      Phototrophs; organisms that uses light as it's source of energy

    • C.

      Autotrophs; organisms that uses organic compounds as its sole carbon source

    • D.

      Organotrophs; an organisms that uses reduced organic compounds as its electron source

    Correct Answer
    C. Autotrophs; organisms that uses organic compounds as its sole carbon source
    Explanation
    The correct answer is "autotrophs; organisms that use organic compounds as its sole carbon source." Autotrophs are organisms that can produce their own food using inorganic substances such as carbon dioxide. They do not rely on organic compounds as a carbon source. Instead, they use light or inorganic chemicals as their source of energy to convert carbon dioxide into organic compounds through processes like photosynthesis or chemosynthesis.

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  • 30. 

    Passive diffusion is an efficient way to move ___ and ___ inside the cell

    • A.

      Gases; water

    • B.

      Gases; glucose

    • C.

      Water; ions

    • D.

      Gases; polar substances

    • E.

      A & B are correct

    Correct Answer
    A. Gases; water
    Explanation
    Passive diffusion is an efficient way to move gases and water inside the cell. This process occurs without the need for energy expenditure and relies on the concentration gradient of the substances involved. Gases, such as oxygen and carbon dioxide, can easily diffuse across the cell membrane due to their small size and nonpolar nature. Water molecules, being small and polar, can also move through the membrane via passive diffusion. Therefore, option A, gases; water, is the correct answer as it accurately identifies the substances that can be efficiently transported through passive diffusion.

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  • 31. 

    On the diagram showing an ABC transporter, number 1 is __ and number 2 is ____

    • A.

      Transporter protein; nucleotide binding domain

    • B.

      Solute binding protein, transporter protein

    • C.

      Nucleotide binding domain; solute binding protein

    • D.

      Solute; solute binding protein

    Correct Answer
    B. Solute binding protein, transporter protein
    Explanation
    In the given diagram of an ABC transporter, number 1 is the solute binding protein. Solute binding proteins are responsible for binding and transporting specific molecules or ions across the cell membrane. Number 2, on the other hand, represents the transporter protein. Transporter proteins are integral membrane proteins that facilitate the movement of molecules or ions across the cell membrane.

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  • 32. 

    Magnetosomes are

    • A.

      Cytoplasmic inclusion found in bacteria

    • B.

      Involved in the movement of microorganisms

    • C.

      Characterized by an intracellular chain of magnetite

    • D.

      Inclusions bacteria uses to orient themselves in Earth's magnetic field

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    Magnetosomes are cytoplasmic inclusions found in bacteria. They are involved in the movement of microorganisms and are characterized by an intracellular chain of magnetite. These inclusions are used by bacteria to orient themselves in Earth's magnetic field. Therefore, all of the given options are correct explanations for magnetosomes.

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  • 33. 

    Which of the following statements about facilitated diffusion is NOT correct

    • A.

      Transport proteins carries molecules across the membrane

    • B.

      Does not require metabolic energy

    • C.

      The rate of diffusion increases with the concentration gradient

    • D.

      Molecules are moved from a less concentrated are to a more concentrated one

    Correct Answer
    D. Molecules are moved from a less concentrated are to a more concentrated one
    Explanation
    Facilitated diffusion is the passive transport of molecules across a membrane with the help of transport proteins. It does not require metabolic energy, as it relies on the concentration gradient to move molecules from an area of higher concentration to an area of lower concentration. Therefore, the statement "molecules are moved from a less concentrated area to a more concentrated one" is not correct. In facilitated diffusion, molecules are always moved from a more concentrated area to a less concentrated one.

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  • 34. 

    Which of the following statements about specimen fixation is NOT correct

    • A.

      Fixation helps inactive enzymes that might disrupt cell morphology

    • B.

      Microorganisms are often killed during the fixation process

    • C.

      Fixation is a mandatory step for cellular observation

    • D.

      Heat fixation is more common than chemical fixation

    • E.

      All of the above are correct

    Correct Answer
    E. All of the above are correct
    Explanation
    All of the above statements are correct. Fixation helps inactivate enzymes that could disrupt cell morphology, microorganisms are often killed during the fixation process, and fixation is indeed a mandatory step for cellular observation. Additionally, heat fixation is indeed more common than chemical fixation.

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  • 35. 

    Some bacteria have complex nutritional requirements and they are referred to as

    • A.

      Complex

    • B.

      Demanding

    • C.

      Particular

    • D.

      Fastidious

    • E.

      Choosy

    Correct Answer
    D. Fastidious
    Explanation
    Fastidious bacteria are those that have complex nutritional requirements. They are referred to as fastidious because they are very selective and demanding in their nutritional needs. These bacteria often require specific nutrients or growth conditions that are not easily met, making them difficult to cultivate in the laboratory. Therefore, the correct answer is "fastidious."

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  • 36. 

    The association of endotoxin in gram-negative bacteria is a result of the presence of 

    • A.

      Peptidoglycan layers in the cell wall

    • B.

      Polypeptides in the plasma membrane

    • C.

      Steroids in the plasma membrane

    • D.

      Lipopolysaccharides in the outer membrane

    Correct Answer
    D. Lipopolysaccharides in the outer membrane
    Explanation
    The correct answer is lipopolysaccharides in the outer membrane. Lipopolysaccharides (LPS) are a major component of the outer membrane of gram-negative bacteria. LPS molecules consist of a lipid portion called lipid A, a core oligosaccharide, and an O antigen. LPS can elicit a strong immune response in the host, leading to the release of pro-inflammatory cytokines. This immune response is responsible for the symptoms of endotoxemia, which can occur in severe bacterial infections. Therefore, the association of endotoxin in gram-negative bacteria is a result of the presence of lipopolysaccharides in the outer membrane.

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  • 37. 

    An internal membrane system is observed is some genus of bacteria that are

    • A.

      Degraders

    • B.

      Photosynthetic

    • C.

      Nitrogen fixers

    • D.

      B & C

    • E.

      A & B

    Correct Answer
    D. B & C
    Explanation
    The correct answer is B & C. An internal membrane system is observed in some genus of bacteria that are both photosynthetic and nitrogen fixers. This means that these bacteria have the ability to convert sunlight into energy through photosynthesis and also have the ability to convert atmospheric nitrogen into a usable form for plants. This internal membrane system is likely involved in these metabolic processes.

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  • 38. 

    Which microbes would resemble those of earliest life forms

    • A.

      Photosynthetic microbes

    • B.

      Viruses

    • C.

      Cyanobacteria

    • D.

      Protists

    • E.

      Archaea

    Correct Answer
    E. Archaea
    Explanation
    Archaea would resemble the microbes of earliest life forms because they are believed to be one of the oldest forms of life on Earth. They are single-celled organisms that can survive in extreme environments, similar to the conditions that existed when life first originated on our planet. Archaea have a simple cellular structure and lack a nucleus, making them more similar to the primitive cells that likely existed billions of years ago. Additionally, their genetic material and metabolic processes are distinct from other forms of life, further supporting their resemblance to early life forms.

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  • 39. 

    The genetic expression machinery of archaea is most similar to 

    • A.

      Monera

    • B.

      Eukaryotes

    • C.

      Bacteria

    • D.

      Prokaryotes

    • E.

      Mitochondria

    Correct Answer
    B. Eukaryotes
    Explanation
    The genetic expression machinery of archaea is most similar to eukaryotes. Archaea and eukaryotes share several similarities in their genetic expression processes, such as the presence of similar RNA polymerases and transcription factors. Additionally, both archaea and eukaryotes have similar mechanisms for mRNA processing and protein translation. These similarities suggest a closer evolutionary relationship between archaea and eukaryotes compared to other options like bacteria, prokaryotes, or mitochondria.

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  • 40. 

    The following statement about bacterial capsules is NOT true

    • A.

      Capsules are required or growth and reproduction in laboratory cultures

    • B.

      Are well organized layers composed of polysaccharides

    • C.

      Are visible in the light microscope when negatively stained

    • D.

      Capsules help pathogenic bacteria resist phagocytosis by host phagocytic cells

    • E.

      Capsules can protect bacterial cells from desiccation due to the high amount of water

    Correct Answer
    A. Capsules are required or growth and reproduction in laboratory cultures
    Explanation
    Bacterial capsules are not required for growth and reproduction in laboratory cultures. While capsules may enhance the growth of certain bacteria in certain conditions, they are not an absolute requirement for growth and reproduction in laboratory cultures.

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  • 41. 

    The correct order of the application of chemicals in the gram stain is

    • A.

      Iodine, crystal violet, safranin, and alcohol

    • B.

      Crystal violet, iodine, alcohol and safranin

    • C.

      Safranin, iodine, crystal violet and alcohol

    • D.

      Alcohol, iodine crystal violet and safranin

    Correct Answer
    B. Crystal violet, iodine, alcohol and safranin
    Explanation
    The correct order of the application of chemicals in the gram stain is crystal violet, iodine, alcohol, and safranin. This is because crystal violet is the primary stain that stains all cells, iodine acts as a mordant to enhance the binding of the stain to the cell wall, alcohol is used as a decolorizer to remove the stain from certain types of cells, and safranin is the counterstain that stains the decolorized cells.

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  • 42. 

    Every cultured microorganism needs a source of 

    • A.

      Carbon, nitrogen and vitamins

    • B.

      Water, carbon and phosphorus

    • C.

      Energy carbon nitrogen and phosphorus

    • D.

      Energy, water, and carbon

    Correct Answer
    C. Energy carbon nitrogen and phosphorus
    Explanation
    Every cultured microorganism requires a source of energy to carry out its metabolic processes, such as growth and reproduction. Carbon is necessary for the synthesis of organic compounds, while nitrogen is essential for the production of proteins and nucleic acids. Phosphorus is required for the synthesis of nucleic acids and ATP, the energy currency of cells. Water is also crucial for maintaining cellular hydration and facilitating various biochemical reactions. Therefore, the correct answer is "energy carbon nitrogen and phosphorus."

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  • 43. 

    Blood agar is often used to observe changes in the appearance of the agar around the colonies growing on this medium. this medium could be called

    • A.

      Selective

    • B.

      Differential

    • C.

      Designated

    • D.

      Defined

    • E.

      Exact

    Correct Answer
    B. Differential
    Explanation
    Blood agar is a type of differential medium. It contains blood which allows for the differentiation of bacteria based on their ability to break down the red blood cells. Bacteria that can break down the red blood cells will appear as clear or transparent zones around the colonies, indicating their hemolytic activity. On the other hand, bacteria that cannot break down the red blood cells will not cause any changes in the appearance of the agar. Therefore, blood agar is often used to observe and differentiate between different types of bacteria based on their hemolytic activity.

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  • 44. 

    The first microbial life forms on earth were major contributores to several processes in the biosphere. on of the option below is NOT an example of the mentioned processes.

    • A.

      Cycling of elements essential for life

    • B.

      Capacity to cause diseases on host cells

    • C.

      Source of nutrients at the base of all ecological food webs

    • D.

      Carrying out of photosynthesis by some of them

    Correct Answer
    B. Capacity to cause diseases on host cells
    Explanation
    The first microbial life forms on earth were major contributors to several processes in the biosphere, including the cycling of elements essential for life, serving as a source of nutrients at the base of all ecological food webs, and carrying out photosynthesis. However, the capacity to cause diseases on host cells is not an example of these mentioned processes. While some microbes can cause diseases, this is not a process that contributes to the overall functioning of the biosphere or the ecological food webs.

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  • 45. 

    A selective media

    • A.

      Favors the growth of a particular microorganism

    • B.

      Distinguish among different groups of microbes

    • C.

      Has its chemical components pre-defined

    • D.

      Contains undefined components such as peptones

    Correct Answer
    A. Favors the growth of a particular microorganism
    Explanation
    A selective media is designed to promote the growth of specific microorganisms while inhibiting the growth of others. It contains certain components, such as antibiotics or dyes, that selectively target and suppress the growth of unwanted microbes. This allows for the isolation and identification of the desired microorganism by creating a favorable environment for its growth while suppressing the growth of competing organisms. The other options, such as distinguishing among different groups of microbes or having pre-defined chemical components, do not accurately describe the purpose or characteristics of a selective media.

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  • 46. 

    Agar is the most common solidifying agent because of the following characteristic(s)

    • A.

      Most microorganisms cannot degrade it

    • B.

      Microbes growing on agar can be inucbated at a wide range of temperatures

    • C.

      It does not harden in temperatures below 45 degrees C

    • D.

      All of the above

    Correct Answer
    D. All of the above
    Explanation
    Agar is the most common solidifying agent because it has the characteristic of being resistant to degradation by most microorganisms. Additionally, agar allows for incubation of microbes at a wide range of temperatures, making it versatile for different types of organisms. Furthermore, agar does not harden at temperatures below 45 degrees C, which allows for easy handling and manipulation in the laboratory. Therefore, all of the given characteristics make agar the preferred choice as a solidifying agent.

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  • 47. 

    Serial dilutions 

    • A.

      Are used to determine the number of viable cells in a culture

    • B.

      Are used to identify viruses

    • C.

      Are used before streaking plates

    • D.

      Are used whenever we have a mixed culture

    Correct Answer
    A. Are used to determine the number of viable cells in a culture
    Explanation
    Serial dilutions are a technique used to determine the number of viable cells in a culture. This process involves diluting a sample multiple times to obtain a range of concentrations. By spreading each diluted sample onto agar plates and allowing the cells to grow, it becomes possible to count the number of colonies formed. The number of colonies can then be used to estimate the number of viable cells in the original culture, as each colony arises from a single viable cell. This method is commonly used in microbiology and other fields to quantify the number of cells present in a sample.

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  • 48. 

    How do we know when the streak plate method was correctly applied

    • A.

      When microorganisms eventually grow on the surface of the plate

    • B.

      When we are able to see two different microorganisms

    • C.

      When colonies grow spatially isolated from each other

    • D.

      When the surface of the medium is kept intact

    Correct Answer
    C. When colonies grow spatially isolated from each other
    Explanation
    The streak plate method is used to isolate individual colonies of microorganisms on a solid medium. When colonies grow spatially isolated from each other, it indicates that the streak plate method was correctly applied. This means that each colony originated from a single microorganism and there was no contamination or merging of colonies. Spatially isolated colonies allow for accurate identification and characterization of individual microorganisms.

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  • 49. 

    The picture on the side show typical results of a 

    • A.

      Streak plate

    • B.

      Spread plate

    • C.

      Serial dilution

    • D.

      Stab inoculation

    Correct Answer
    B. Spread plate
    Explanation
    A spread plate is a method used in microbiology to isolate and count bacterial colonies. It involves spreading a small amount of a liquid sample containing bacteria onto the surface of an agar plate using a sterile spreader. The bacteria are evenly distributed across the plate, allowing individual colonies to grow and be easily counted. The picture on the side likely shows the results of a spread plate, displaying distinct bacterial colonies that have grown on the agar surface.

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  • 50. 

    Phosphorus is considered a macronutrient. its importance to cell relies on the fact that

    • A.

      It is present in nucleotides

    • B.

      It is present in some proteins

    • C.

      It is present in phospholipids

    • D.

      It is present in several cofactors

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    Phosphorus is considered a macronutrient because it is essential for various cellular functions. It is present in nucleotides, which are the building blocks of DNA and RNA, playing a crucial role in genetic information transfer. Additionally, phosphorus is present in some proteins, contributing to their structure and function. It is also a key component of phospholipids, which are essential for cell membrane structure. Furthermore, phosphorus is present in several cofactors, which are molecules that assist in enzyme activity. Therefore, all of these factors highlight the importance of phosphorus to cellular processes.

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Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.

  • Current Version
  • May 08, 2024
    Quiz Edited by
    ProProfs Editorial Team
  • May 05, 2012
    Quiz Created by
    Cassiebeermann
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