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Questions and Answers
Which of the following viruses is characterized by a polyhedral capsid and fibers at each corner?
Which of the following viruses is characterized by a polyhedral capsid and fibers at each corner?
The T-even bacteriophage has a helical tail.
The T-even bacteriophage has a helical tail.
True
What kind of genetic material do DNA viruses contain?
What kind of genetic material do DNA viruses contain?
DNA
The __________ bacteriophage possesses a polyhedral capsid and a helical tail.
The __________ bacteriophage possesses a polyhedral capsid and a helical tail.
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Match the following characteristics with their respective viruses:
Match the following characteristics with their respective viruses:
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What is a common feature of RNA viruses?
What is a common feature of RNA viruses?
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Fibers are common structural components found in all types of viruses.
Fibers are common structural components found in all types of viruses.
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What structure is commonly found at each corner of the adenovirus?
What structure is commonly found at each corner of the adenovirus?
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What is the first step in the viral replication cycle?
What is the first step in the viral replication cycle?
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The lytic cycle involves the integration of viral DNA into the bacterial DNA.
The lytic cycle involves the integration of viral DNA into the bacterial DNA.
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What occurs during the integration step of the lysogenic cycle?
What occurs during the integration step of the lysogenic cycle?
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New viruses leave the host cell during the ______ stage.
New viruses leave the host cell during the ______ stage.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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Which step follows penetration in the viral replication cycle?
Which step follows penetration in the viral replication cycle?
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In the lytic cycle, new viruses are produced and released at the same stage.
In the lytic cycle, new viruses are produced and released at the same stage.
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Name a key difference between the lytic and lysogenic cycles.
Name a key difference between the lytic and lysogenic cycles.
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What is the first step in the lytic cycle of a phage?
What is the first step in the lytic cycle of a phage?
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The viral DNA enters the host cell before the attachment of the phage.
The viral DNA enters the host cell before the attachment of the phage.
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What structure of the phage is responsible for binding to the host cell?
What structure of the phage is responsible for binding to the host cell?
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The phage injects its genome into the ______ of the host cell.
The phage injects its genome into the ______ of the host cell.
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Match the following stages of the lytic cycle with their descriptions:
Match the following stages of the lytic cycle with their descriptions:
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Which of the following describes the role of host-specific match in phage attachment?
Which of the following describes the role of host-specific match in phage attachment?
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Biosynthesis is the stage where new viral components are produced.
Biosynthesis is the stage where new viral components are produced.
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What happens during the penetration step of the lytic cycle?
What happens during the penetration step of the lytic cycle?
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What enzyme do retroviruses like HIV use to convert RNA into DNA?
What enzyme do retroviruses like HIV use to convert RNA into DNA?
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Retroviruses are released from the host cell by lysis.
Retroviruses are released from the host cell by lysis.
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In the process of reverse transcription, what does RNA get converted into?
In the process of reverse transcription, what does RNA get converted into?
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The process by which viral components are synthesized in a host cell is called __________.
The process by which viral components are synthesized in a host cell is called __________.
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Match the following viral processes with their definitions:
Match the following viral processes with their definitions:
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What happens to cDNA integrated into the host DNA?
What happens to cDNA integrated into the host DNA?
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Budding is the method by which most viruses are released from host cells.
Budding is the method by which most viruses are released from host cells.
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During the __________ phase of viral reproduction, remaining viral components assemble to form new virus particles.
During the __________ phase of viral reproduction, remaining viral components assemble to form new virus particles.
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Which of the following statements about antibiotics is correct?
Which of the following statements about antibiotics is correct?
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Archaea contain peptidoglycan in their cell walls.
Archaea contain peptidoglycan in their cell walls.
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What is a major characteristic of methanogens?
What is a major characteristic of methanogens?
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Archaea are now thought to be more closely related to __________ than to bacteria.
Archaea are now thought to be more closely related to __________ than to bacteria.
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Match the antibiotic with its function:
Match the antibiotic with its function:
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What type of organism obtains energy by oxidizing inorganic chemicals?
What type of organism obtains energy by oxidizing inorganic chemicals?
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Mutualism refers to a relationship where one population benefits at the expense of another.
Mutualism refers to a relationship where one population benefits at the expense of another.
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Which type of bacteria benefit from living in the human intestines by releasing vitamins K and B12?
Which type of bacteria benefit from living in the human intestines by releasing vitamins K and B12?
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Bacteria such as __________ and __________ form resistant endospores under unfavorable conditions.
Bacteria such as __________ and __________ form resistant endospores under unfavorable conditions.
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Match the following relationships with their definitions:
Match the following relationships with their definitions:
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Which of the following is true about parasitic bacteria?
Which of the following is true about parasitic bacteria?
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Endospores can be destroyed by ultraviolet radiation.
Endospores can be destroyed by ultraviolet radiation.
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What type of bacteria primarily depend on organic molecules for both carbon and energy?
What type of bacteria primarily depend on organic molecules for both carbon and energy?
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Study Notes
Viruses
- Viruses are very small, approximately 20-300nm.
- Characterized by: size and shape (helical, polyhedral, complex); presence or absence of outer envelope; type of nucleic acid (DNA/RNA).
- Viruses have at least two parts: covering (capsid, envelope) and inner core (nucleic acid).
- Some viruses have an outer envelope surrounding the capsid.
- The capsid is an outer protein coat made of protein subunits called capsomers.
- The nucleic acid core contains DNA or RNA.
- Viruses can only reproduce within a host cell.
The Human Microbiome
- The human microbiome is the community of microorganisms in a specific environment
- A recent study from the American Academy of Microbiology estimated each human ecosystem contains roughly 100 trillion microbial cells and just 37 trillion human cells.
Course Outline
- The course will cover Viruses, The Prokaryotes, The Bacteria, and The Archaea.
Learning Outcomes
- Explain the basic structure and life cycle of a virus.
- Explain the basic structure and characteristics of bacteria and archaea.
- Relate the importance of microorganisms in life.
Lesson 01: Viruses
- Viruses are obligate intracellular parasites.
- They can only reproduce within host cells.
- Viruses are incapable of replicating their own genetic material.
- Once inside a living cell, they hijack the cell's protein synthesis machinery to replicate nucleic acids, capsids, and viral enzymes.
Lesson 02: The Prokaryotes
- Prokaryotes range in length from 1 to 5 µm.
- They are mainly unicellular.
- They lack a membrane-bound nucleus and other membrane-bound organelles.
- Most prokaryotes have a cell wall, primarily composed of peptidoglycan.
- Some prokaryotes produce a capsule or slime layer surrounding the cell wall.
- The capsule helps protect the bacteria from phagocytosis and enables attachment to surfaces.
Lesson 03: Bacteria
- Bacteria are often identified using Gram staining.
- Gram-positive bacteria retain the dye, appearing purple.
- Gram-negative bacteria lose the dye, appearing pink.
- The difference in staining is due to the cell wall structure.
- Bacteria can be categorized by their shape (cocci, bacilli, spirilla).
Lesson 04: Archaea
- Archaea were previously classified as bacteria.
- They lack peptidoglycan in their cell walls.
- Their cell walls have a different structure.
- Archaea are biochemically more similar to eukaryotes than to bacteria.
- Many archaea live in harsh conditions (extremophiles).
- One example group are methanogens which produce methane.
Prokaryotic Reproduction
- Prokaryotes reproduce asexually through binary fission.
- Genetic material can be exchanged through transduction, conjugation, or transformation.
Bacterial Oxygen Requirements
- Bacteria have different oxygen requirements.
- Obligate aerobes require oxygen.
- Obligate anaerobes cannot tolerate oxygen.
- Facultative anaerobes can grow in the presence or absence of oxygen.
Modes of Nutrition
- Autotrophs make their own food.
- Photoautotrophs use sunlight.
- Chemoautotrophs use inorganic chemicals.
- Heterotrophs get energy from other organisms.
- Photoheterotrophs obtain energy from sunlight but need organic molecules for carbon.
- Chemoheterotrophs obtain carbon and energy from organic compounds.
Prokaryote Relationships
- Prokaryotes interact with other organisms in various ways, including commensalism (one species benefits, the other is unaffected), mutualism (both benefit), and parasitism (one benefits at the expense of the other).
Bacteriophages: Lytic and Lysogenic Cycles
- Bacteriophages infect bacteria.
- In the lytic cycle, the virus replicates and causes the host cell to burst, releasing new viruses.
- In the lysogenic cycle, the viral DNA integrates into the host cell's DNA. This viral DNA is now called a prophage.
- The lysogenic cycle can stay dormant, or the prophage will restart the cycle and enter the lytic phase.
Retroviruses
- Retroviruses contain reverse transcriptase.
- Reverse transcriptase converts viral RNA to DNA.
- The viral DNA then integrates into the host cell's DNA, forming a provirus.
- Retroviruses replicate when the host DNA replicates.
Antibiotics
- Antibiotics can inhibit protein synthesis or cell wall biosynthesis.
- Bacterial resistance to antibiotics is a significant concern.
Summary of Virus Subtopics
- Viruses have a covering (capsid or an additional envelope) and an inner core (nucleic acid).
- Viruses are obligate intracellular parasites, host-specific, and differ significantly in their structure
- Viruses can have lytic or lysogenic cycles.
- Retroviruses utilize reverse transcription (RNA to DNA) during reproduction.
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Description
This quiz explores the fundamental aspects of viruses, including their structure, classification, and life cycle. Additionally, it covers the human microbiome and its role in the ecosystem. Enhance your understanding of microbial life and its implications for human health.
