Acellular Pathogens: Viruses Quiz

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Questions and Answers

What characterizes reverse zoonoses?

Spread of a virus solely through environmental sources.

Infection of an animal by a virus that originated in a human. (correct)

Infection of a human by a virus originating in an animal.

Transmission of a virus from animal to human.

Which statement best describes the size of virions?

Virions vary greatly in size but are never larger than $10nm$.

Virions are generally larger than prokaryotic cells.

Virions can only be observed under a regular light microscope.

Virions typically range from $20nm$ to $900nm$, smaller than most cells. (correct)

What role did Wendell Stanley play in the field of virology?

He discovered how to transmit viruses through water.

He was the first to crystallize the structure of a virus. (correct)

He was the first person to isolate DNA viruses.

He invented the first vaccine for bacterial infections.

Why are bacteriophages not a concern in human food?

They are specific to bacteria and do not infect human cells. Signup and view all the answers

What was the contribution of Stanley's work to the development of vaccines?

Clarification of the RNA structure in viruses leading to vaccine development. Signup and view all the answers

What is the term used to describe the variety of organisms that a virus can infect?

Host range Signup and view all the answers

Which statement best describes how viruses reproduce?

They require a host cell's genome to reproduce. Signup and view all the answers

What mechanism involves an arthropod carrying a virus on the outside of its body?

Mechanical transmission Signup and view all the answers

Which type of virus specifically infects bacterial cells?

Bacteriophages Signup and view all the answers

What characterizes viruses that are classified as zoonotic?

They are transmitted from animals to humans. Signup and view all the answers

Which of the following is NOT a characteristic of viruses?

They can reproduce on their own. Signup and view all the answers

What is a major challenge in treating infections caused by viruses?

Viruses mutate quickly, making stand-alone treatments ineffective. Signup and view all the answers

Which component surrounds the viral genome and aids in infectivity?

Protein capsid Signup and view all the answers

What is the primary role of bacteriophages in the viral life cycle?

To infect bacterial cells and replicate within them Signup and view all the answers

Which mechanism is primarily responsible for the transmission of the Ebola virus?

Direct contact with bodily fluids of infected individuals Signup and view all the answers

Which of the following correctly describes host range specificity in viruses?

Only certain species or cells can be infected by a specific virus Signup and view all the answers

What differentiates viroids from viruses?

Viroids lack a protein coat Signup and view all the answers

What is a common consequence of viral infection on a host cell?

Lysis of the host cell releasing new viral particles Signup and view all the answers

Which historical practice was used to prevent smallpox before modern vaccines were developed?

Inoculation or variolation Signup and view all the answers

In the context of viral infections, what defines a 'viral epidemic'?

A sudden rise in the number of cases of a viral disease in a specific area Signup and view all the answers

What method is crucial for isolating viruses in the laboratory?

Cell culture techniques Signup and view all the answers

Study Notes

Acellular Pathogens: Viruses

Viruses are tiny, filterable agents smaller than bacteria, discovered in 1892.
Dmitri Ivanovski identified tobacco mosaic disease (TMD) as caused by a filterable agent, not a bacterium.
Unlike cellular organisms, viruses are acellular, meaning they're not composed of cells.
To reproduce, viruses must infect a host cell.
Viruses' genomes enter host cells and direct the creation of new viral components (proteins and nucleic acids).
New virions are assembled within the host cell and release the viral genome into another host cell for continued infection.
Viruses are obligate intracellular parasites.
Viruses have a protein capsid surrounding their genome (DNA or RNA, never both).
Some viruses also have a phospholipid membrane with viral glycoproteins.
Viruses lack genes for many vital functions, relying on host cells for reproduction.
Viruses' evolutionary origins are unclear and not included in the tree of life.

Viral Epidemics and History

Public health measures have dramatically decreased viral mortality, but epidemics can spread globally.
The 2009 H1N1 influenza outbreak and the 2014 Ebola outbreak are examples of this global spread.
Inoculation (variolation) methods were used to prevent smallpox as early as the 17th century.
Edward Jenner developed vaccination using cowpox to prevent smallpox in the late 18th century.
Electron microscopes allowed visualization of viruses, aiding understanding of structure in the late 1930s.

Viral Hosts and Transmission

Viruses can infect various organisms (plants, animals, bacteria, archaea).
Host range varies, with some infecting specific hosts and cells.
Bacteriophages infect bacteria.
Viral effects range from cell death to altered cell growth to no visible effect.
Transmission occurs through direct / indirect contact (fomites) or vectors (e.g., arthropods).
Viruses can move between animal and human hosts (zoonoses), and in reverse.

Viral Structure and Discovery

Virions are too small to be seen with light microscopes, ranging from 20 to 900 nm.
Giant viruses (e.g., Pandoravirus salinus, Pithovirus sibericum) are larger, approaching bacterial cell sizes.
Wendell Stanley crystallized the tobacco mosaic virus in 1935, revealing protein and RNA composition.
Subsequent research furthered understanding of viral structure.

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Description

Test your knowledge on acellular pathogens, specifically viruses. This quiz covers the discovery, structure, reproduction, and classification of viruses, their role as obligate intracellular parasites, and their impact on host cells. Dive into the fascinating world of viral biology and epidemics.