Viruses and Their Interactions with Host Cells

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Questions and Answers

What does a virus introduce into a host cell upon entry?

Carbohydrates

Lipids

Proteins

Genetic material (correct)

What role does the virus play in the metabolism of the host cell?

It directs the metabolism to produce viral components. (correct)

It enhances the host cell's normal activities.

It destroys the host cell.

It completely shuts down the host cell functions.

What types of genetic material can viruses utilize?

Only DNA

Both DNA and RNA (correct)

Proteins and amino acids

Only RNA

After a virus enters a host cell, what does it primarily aim to produce?

Viruses copies and proteins Signup and view all the answers

During viral infection, what happens to the host cell's normal functions?

They are completely taken over by the virus. Signup and view all the answers

Which type of viruses is more stable in harsh conditions?

Naked viruses Signup and view all the answers

What can destroy enveloped viruses?

Heat and detergents Signup and view all the answers

Which solvents are effective against enveloped viruses?

Alcohol and ether Signup and view all the answers

Compared to naked viruses, what characteristic makes enveloped viruses less stable?

Sensitivity to environmental factors Signup and view all the answers

What is a primary reason enveloped viruses are more easily destroyed than naked viruses?

Enveloped viruses have a lipid membrane Signup and view all the answers

What is the primary mode of transmission of COVID-19?

Close contact through droplet infection Signup and view all the answers

Which statement correctly describes how COVID-19 spreads?

Through droplet infection during close contact Signup and view all the answers

Which of the following is NOT a mode of transmission for COVID-19?

Fecal-oral route Signup and view all the answers

How does droplet infection occur in the context of COVID-19?

During close contact with an infected individual Signup and view all the answers

Why is close contact important in the transmission of COVID-19?

It increases the likelihood of droplet infection Signup and view all the answers

What constitutes a complete virus particle?

A core of nucleic acid and a protein coat Signup and view all the answers

What is the term used for the combination of nucleic acid and the protein coat in a virus?

Nucleocapsid Signup and view all the answers

Which component is NOT part of a typical complete virus particle?

Cell wall Signup and view all the answers

In a virus, what is the primary function of the capsid?

To protect the nucleic acid Signup and view all the answers

What are the two main parts of a virus as described?

Nucleic acid and protein coat Signup and view all the answers

What occurs during the uncoating process of a virus?

The protein coat of the virus is removed. Signup and view all the answers

Which enzyme system primarily facilitates the uncoating of a virus?

Host cell lysosomal enzymes Signup and view all the answers

What is released after uncoating that is essential for replication?

Nucleic acid Signup and view all the answers

What is the role of the capsid in viral uncoating?

It protects the viral nucleic acid. Signup and view all the answers

What is the immediate fate of the nucleic acid after uncoating?

It becomes available for replication. Signup and view all the answers

What is the primary focus of indirect methods in detecting viruses?

Detection of antibodies against the virus Signup and view all the answers

Which of the following would NOT be considered an indirect method of virus detection?

Plasma virus load measurement Signup and view all the answers

In the context of indirect methods, what do skin tests primarily evaluate?

Immune response to the suspected virus Signup and view all the answers

Why might indirect methods be preferred over direct methods in some cases?

They are often quicker and less invasive Signup and view all the answers

What type of sample is typically tested when using indirect methods for virus detection?

Serum samples Signup and view all the answers

Study Notes

General Virology

Viruses infect all organisms in nature, including bacteria, plants, and animals.
Bacteriophages are viruses that infect bacteria.
Plant viruses infect plants.
Animal viruses infect vertebrates, including humans.

Properties Differentiating Viruses from Bacteria

Size: Viruses are tiny (20-300nm), requiring an electron microscope to see most, except poxviruses.
Genome: Viruses have either DNA or RNA, but never both, in their genetic material.
Metabolically: Viruses lack metabolic activity outside a host cell; they have no ribosomes or protein-synthesizing apparatus.

Structure of Viruses

Virion: The complete virus particle.
Nucleocapsid: The core of nucleic acid (genome) surrounded by a protein coat (capsid).
Enveloped viruses: Some viruses have an outer lipid-containing envelope, while others are non-enveloped (naked).

Viral Nucleic Acid

Viruses have either DNA or RNA as their genetic material.
Most DNA viruses have double-stranded DNA, except parvoviruses.
Most RNA viruses have single-stranded RNA, except reoviruses.
The viral genome is the infectious part of the virus.

Capsid (Protein Coat)

The capsid protects the genetic material and mediates attachment to host cell receptors; it's made of capsomeres.
It is antigenic, inducing neutralizing antibodies and activating cytotoxic T lymphocytes to kill infected cells.

Viral Envelope

Lipid component derived from host cell membrane.
Protein component is virus-specific.
Frequently has glycoprotein spikes.
Glycoprotein spikes mediate attachment to host cell receptors.
Loss of the envelope inhibits attachment and infectivity.
Enveloped viruses are less stable than naked viruses, as they are destroyed by heat, detergents, and lipid solvents (e.g., alcohol or ether).

Viral Classification

Classification can be based on symptomatology (tropism) or hierarchically based on viral taxonomy.
The viral classification scheme is based on factors like nucleic acids (DNA or RNA), replication strategies, and the presence/absence of an envelope.

Coronaviruses

Coronaviruses are a large family of viruses that cause various illnesses, including the common cold.
Severe Acute Respiratory Syndrome (SARS-CoV) and Middle East Respiratory Syndrome (MERS-CoV) are examples of more severe diseases.
COVID-19 is also known as SARS-CoV-2.
COVID-19 began as an acute pneumonia outbreak in China in late 2019, quickly becoming a pandemic.
COVID-19 transmission is primarily by droplet infection, spreading from infected individuals to others by close contact.
A coronavirus is typically a spherical, enveloped particle with single-stranded RNA surrounded by a capsid, with glycoprotein spikes on its surface.

Viral Replication

Viruses replicate within host cells, utilizing host cell machinery, with no independent metabolic capabilities.
Replication involves stages of attachment, penetration, uncoating, replication, assembly, and release.
Penetration mechanisms include endocytosis for non-enveloped viruses and fusion for enveloped viruses.

Fate of Viral Infections

Inapparent: Viral infection without symptoms.
Apparent: Clinical infection (e.g. localized or systemic).
Persistent: The virus persists, either chronic (continuous virus detection) or latent (dormant).

Laboratory Diagnosis of Viral Infection

Direct methods detect the virus or its components.
Indirect methods detect antibodies against viruses.

Treatment of Viral Infections

Antivirals target specific viral replication steps, without harming host cells.
The number of widely available antiviral drugs is fewer than antibacterial drugs.

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Description

This quiz explores the intricate relationship between viruses and their host cells, covering topics such as viral entry, metabolism effects, and modes of transmission, particularly focusing on COVID-19. Test your knowledge on the stability of different types of viruses and the solvents that impact them.