Microbiology Exam Prep V3

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Microbiology Exam Prep V3 - Quiz

Microbiology ese prep v3


Questions and Answers
  • 1. 

    Which of the following is not true about spikes?

    • A.

      They are used for absorption

    • B.

      They are used for penetration

    • C.

      They may cause haemagglutination

    • D.

      They are only found on enveloped viruses

    Correct Answer
    B. They are used for penetration
    Explanation
    The statement "they are used for penetration" is not true about spikes. Spikes are protein structures on the surface of viruses that are used for attachment and entry into host cells, but they do not directly penetrate the host cell. Instead, they facilitate the fusion of the viral envelope with the host cell membrane, allowing the virus to enter the cell.

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  • 2. 

    The ability of a virus to infect an organism is regulated by

    • A.

      The host species

    • B.

      The type of cells

    • C.

      The availability of an attachment site

    • D.

      Cell factors necessary for replication

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    The ability of a virus to infect an organism is regulated by multiple factors, including the host species, the type of cells it can infect, the availability of an attachment site, and the presence of cell factors necessary for replication. All of these factors play a role in determining whether a virus can successfully infect an organism.

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  • 3. 

    Which of the following statements is not true?

    • A.

      Viruses contain DNA or RNA

    • B.

      The nucleic acid of a virus is surrounded by a protein coat

    • C.

      Viruses multiply inside living cells using viral mRNA, tRNA and ribosomes

    • D.

      Viruses cause the synthesis of specialised infectious elements

    • E.

      Viruses multiply inside living cells

    Correct Answer
    C. Viruses multiply inside living cells using viral mRNA, tRNA and ribosomes
    Explanation
    The given correct answer is "viruses multiply inside living cells using viral mRNA, tRNA and ribosomes." This statement is not true because viruses do not have their own mRNA, tRNA, or ribosomes. Instead, they rely on the host cell's machinery to replicate and produce new viral particles. Viruses inject their genetic material into a host cell, and then hijack the cell's machinery to produce viral proteins and replicate their genetic material.

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  • 4. 

    A viroid is

    • A.

      A complete infectious virus particle

    • B.

      A naked infectious piece of RNA

    • C.

      A capsid without any nucleic acid

    Correct Answer
    B. A naked infectious piece of RNA
    Explanation
    A viroid is a naked infectious piece of RNA. Unlike a complete infectious virus particle, which consists of both nucleic acid and a protein capsid, a viroid lacks a protein coat and is composed solely of RNA. Viroids are smaller and simpler than viruses, and they can cause diseases in plants by interfering with the normal functioning of the host cell. Their ability to replicate and spread within plants without a protein coat makes them unique and distinct from viruses.

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  • 5. 

    An enveloped virus acquires its envelope during _____________

    • A.

      Penetration

    • B.

      Adsoprtion

    • C.

      Uncoating

    • D.

      Release

    Correct Answer
    D. Release
    Explanation
    An enveloped virus acquires its envelope during the release phase of its life cycle. After the virus has replicated inside the host cell, it needs to exit the cell in order to infect other cells. During the release phase, the virus buds off from the host cell, taking a portion of the host cell's membrane with it. This membrane becomes the envelope of the virus, which is essential for its ability to infect new cells.

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  • 6. 

    The most conclusive evidence that viruses cause cancers is provided by

    • A.

      Finding oncogenes in viruses

    • B.

      The presence of antibodies against viruses in cancer patients

    • C.

      Cancer following the injection of cell-free filtrates

    • D.

      Treating cancer with antibodies

    • E.

      Some liver cancer patients having had hepatitis

    Correct Answer
    C. Cancer following the injection of cell-free filtrates
    Explanation
    The most conclusive evidence that viruses cause cancers is provided by cancer following the injection of cell-free filtrates. This suggests that the filtrates contain a virus that is capable of causing cancer in the injected individuals. This direct link between injecting the filtrates and the development of cancer provides strong evidence of the role of viruses in causing cancer. Other options such as finding oncogenes in viruses, the presence of antibodies against viruses in cancer patients, treating cancer with antibodies, and some liver cancer patients having had hepatitis, may also suggest a potential association between viruses and cancer, but they do not provide as direct and conclusive evidence as the injection of cell-free filtrates.

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  • 7. 

    Generally, in a DNA-virus infection, the host animal cell supplies all of the following except

    • A.

      RNA polymerase

    • B.

      Nucleotides

    • C.

      DNA polymerase

    • D.

      TRNA

    • E.

      None of the above

    Correct Answer
    C. DNA polymerase
    Explanation
    In a DNA-virus infection, the host animal cell supplies all the necessary components for viral replication except DNA polymerase. DNA polymerase is an enzyme responsible for synthesizing new DNA strands during replication. The host cell's RNA polymerase is used by the virus to transcribe its genetic material, nucleotides are used as building blocks for DNA synthesis, and tRNA is involved in protein synthesis. However, the virus must bring its own DNA polymerase in order to replicate its DNA.

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  • 8. 

    Which of the following is most useful in determining whether two organisms are related?

    • A.

      If both ferment lactose

    • B.

      If both are gram-positive

    • C.

      If both are motile

    • D.

      If both are aerobic

    • E.

      All are equally important

    Correct Answer
    B. If both are gram-positive
    Explanation
    If both organisms are gram-positive, it indicates that they have a similar cell wall structure, which suggests a closer evolutionary relationship. Gram-positive bacteria have a thick peptidoglycan layer in their cell walls, which differentiates them from gram-negative bacteria. This similarity in cell wall composition suggests that these organisms may have a common ancestor and are therefore more closely related.

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  • 9. 

    Into which group would you place a photosynthetic cell that lacks a nucleus?

    • A.

      Animalia

    • B.

      Bacteria

    • C.

      Fungi

    • D.

      Plantae

    Correct Answer
    B. Bacteria
    Explanation
    A photosynthetic cell that lacks a nucleus would be placed in the group Bacteria. This is because bacteria are prokaryotes, which are organisms that lack a nucleus and other membrane-bound organelles. They have a simpler structure compared to eukaryotes, such as the cells found in Animalia, Fungi, and Plantae. Bacteria are capable of photosynthesis through various mechanisms, such as using pigments like chlorophyll or bacteriochlorophyll to capture light energy and convert it into chemical energy.

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  • 10. 

    Which of the following is a characteristic of Clostridium?

    • A.

      Endospore-forming cocci

    • B.

      Mycobacteria

    • C.

      Gram-negative aerobic cocci

    • D.

      Anaerobic gram-negative rods

    • E.

      None of the above

    Correct Answer
    A. Endospore-forming cocci
    Explanation
    Clostridium is a genus of bacteria that is known for its ability to form endospores. Endospores are a dormant and highly resistant form of the bacteria that allows it to survive in harsh conditions. The other options listed in the question, such as mycobacteria, gram-negative aerobic cocci, and anaerobic gram-negative rods, do not accurately describe the characteristics of Clostridium. Therefore, the correct answer is endospore-forming cocci.

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  • 11. 

    Which of the following do you expect to be most resistant to high temperatures?

    • A.

      Bacillus subtilis

    • B.

      Eschericia coli

    • C.

      Neisseria gonorrhoeae

    • D.

      Staphylococcus aureus

    • E.

      Streptococcus pyogenes

    Correct Answer
    A. Bacillus subtilis
    Explanation
    Bacillus subtilis is expected to be most resistant to high temperatures because it is a spore-forming bacterium. Spore formation is a survival mechanism that allows certain bacteria to enter a dormant state and withstand harsh conditions such as high temperatures. This ability to form spores makes Bacillus subtilis more resistant to heat compared to the other bacteria listed, which do not have the same capability.

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  • 12. 

    Which of the following lacks a cell wall?

    • A.

      Eschericia

    • B.

      Mycoplasma

    • C.

      Mycobacterium

    • D.

      Clostridium

    • E.

      Streptococcus

    Correct Answer
    B. Mycoplasma
    Explanation
    Mycoplasma lacks a cell wall. This is because Mycoplasma is a type of bacteria that belongs to the class Mollicutes, which are known for their lack of a rigid cell wall. Instead, Mycoplasma has a flexible cell membrane that allows it to take on different shapes and sizes. This lack of a cell wall makes Mycoplasma more susceptible to osmotic pressure and antibiotics that target cell wall synthesis.

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  • 13. 

    Rickettsias differ from chlamydias in that rickettsias

    • A.

      Are gram-negative

    • B.

      Are intracellular parasites

    • C.

      Require an arthropod for transmission

    • D.

      All of the above

    • E.

      None of the above

    Correct Answer
    C. Require an arthropod for transmission
    Explanation
    Rickettsias require an arthropod for transmission, which means they rely on arthropods like ticks, fleas, or lice to spread from one host to another. This is in contrast to chlamydias, which do not require an arthropod for transmission. The other options, being gram-negative and intracellular parasites, are characteristics that both rickettsias and chlamydias share, so they do not differentiate between the two. Therefore, the correct answer is that rickettsias require an arthropod for transmission.

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  • 14. 

    Chemotaxis implies that bacteria:

    • A.

      Move towards an attractant

    • B.

      Move away from a repellant

    • C.

      Both a and b

    • D.

      Neither a nor b

    Correct Answer
    A. Move towards an attractant
    Explanation
    Chemotaxis refers to the movement of bacteria in response to chemical gradients in their environment. When bacteria exhibit chemotaxis, they are capable of detecting and moving towards an attractant, such as a nutrient or favorable condition. Therefore, the correct answer is that bacteria move towards an attractant.

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  • 15. 

    The best definition of HUMORAL immunity is:

    • A.

      Immunity involving soluble antibodies

    • B.

      Immunity involving STEM CELLS

    • C.

      Immunity involving the lymphatics system

    • D.

      Immunity involving T cells

    • E.

      Immunity involving platelets

    Correct Answer
    A. Immunity involving soluble antibodies
    Explanation
    Humoral immunity refers to the immune response mediated by soluble antibodies, which are proteins produced by B cells. These antibodies circulate in the blood and lymphatic system, targeting and neutralizing pathogens or foreign substances. This type of immunity is distinct from cellular immunity, which involves T cells directly attacking infected cells. Therefore, the correct answer is "immunity involving soluble antibodies."

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  • 16. 

    The most common type of antibody in the serum is:

    • A.

      IgG

    • B.

      IgE

    • C.

      IgM

    • D.

      IgA

    • E.

      IgD

    Correct Answer
    A. IgG
    Explanation
    IgG is the most common type of antibody found in the serum. It plays a crucial role in the immune system by providing long-term protection against infections. IgG antibodies are able to cross the placenta, providing passive immunity to newborns. They also help in opsonization, neutralization of toxins, and activation of complement system. IgG antibodies are produced in response to a wide range of pathogens and are involved in both primary and secondary immune responses.

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  • 17. 

    Each antibody has THREE binding sites, one at the end of each arm of the "Y"

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    Antibodies actually have two binding sites, one at the end of each arm of the "Y". Each binding site consists of a specific region called the antigen-binding fragment (Fab), which is responsible for binding to antigens. Therefore, the correct answer is false.

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  • 18. 

    Each antigen-binding site of an antibody molecule is composed of:

    • A.

      The Fc domain

    • B.

      The light chains

    • C.

      The variable domains of one light and one heavy chain

    • D.

      The constant domains of one light and one heavy chain

    • E.

      The variable domains of two light chains

    Correct Answer
    C. The variable domains of one light and one heavy chain
    Explanation
    The antigen-binding site of an antibody molecule is composed of the variable domains of one light and one heavy chain. These variable domains contain the hypervariable regions, also known as the complementarity-determining regions (CDRs), which are responsible for binding to specific antigens. The light chains and constant domains of the light and heavy chains are not directly involved in antigen binding. Therefore, the correct answer is the variable domains of one light and one heavy chain.

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  • 19. 

    Antigenic peptides that are presented by antigen presenting cells are called:

    • A.

      Fc fragments

    • B.

      Secretory fragments

    • C.

      Epitopes

    • D.

      Antibodies

    Correct Answer
    C. Epitopes
    Explanation
    Antigenic peptides that are presented by antigen presenting cells are called epitopes. Epitopes are specific regions on an antigen that are recognized by the immune system. They are responsible for eliciting an immune response and can bind to antibodies or T cell receptors. Antigen presenting cells, such as dendritic cells, macrophages, and B cells, present these epitopes to T cells to initiate an immune response. Fc fragments and secretory fragments are not directly involved in antigen presentation, and antibodies are molecules produced by B cells in response to an antigen.

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  • 20. 

    An important characteristic of IgA is:

    • A.

      It is found in secretions

    • B.

      It can cross the placenta

    • C.

      It is the first Ab secreted in response to antigen stimulation

    • D.

      All of the above

    Correct Answer
    A. It is found in secretions
    Explanation
    IgA is an immunoglobulin that is primarily found in secretions such as tears, saliva, mucus, and breast milk. It plays a crucial role in mucosal immunity by preventing pathogens from entering the body through these secretions. Unlike other immunoglobulins, IgA cannot cross the placenta, which means it does not provide passive immunity to the fetus. While it is one of the first antibodies secreted in response to antigen stimulation, it is not the very first antibody produced. Therefore, the correct answer is that IgA is found in secretions.

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  • 21. 

    The secondary immune resonse

    • A.

      Display a more rapid onset than primary responses

    • B.

      Reach higher maximum levels than primary responses

    • C.

      Display a more acute rise (steeper slope) in immune activity over time than primary resonses

    • D.

      Will often prevent disease

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    The secondary immune response refers to the immune response that occurs upon re-exposure to a previously encountered pathogen. It is characterized by a more rapid onset compared to the primary response, as the immune system has already been primed and is ready to respond. The secondary response also reaches higher maximum levels of immune activity, as the immune system has a memory of the pathogen and can mount a stronger and more efficient response. Additionally, the secondary response displays a more acute rise in immune activity over time, with a steeper slope, compared to the primary response. Finally, the secondary response is often able to prevent disease by effectively eliminating the pathogen before it can cause significant harm. Therefore, all of the above statements are true regarding the secondary immune response.

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  • 22. 

    Opsonisation

    • A.

      Is mediated by the interaction of antibodies with the Fc receptors on phagocytes

    • B.

      Results in more efficient ingestion of antigen by phagocytes

    • C.

      Is important in resisting and/or fighting many bacterial infections

    • D.

      Is particularly well-mediated by several of IgG

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    Opsonisation is a process in which antibodies bind to antigens, marking them for ingestion by phagocytes. This interaction between antibodies and Fc receptors on phagocytes enhances the efficiency of phagocytosis. Opsonisation plays a crucial role in resisting and fighting bacterial infections. It is particularly effective when mediated by several subclasses of IgG antibodies. Therefore, all of the statements mentioned in the options are correct and contribute to the explanation of opsonisation.

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  • Current Version
  • Mar 22, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Jun 11, 2008
    Quiz Created by
    Jaymunro
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