Virology: Capsid Structure and Functions

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Questions and Answers

What type of virus is characterized by having 20 flat sides?

Naked virus

Helical virus

Complex virus

Icosahedral virus (correct)

Which mode of transmission is exemplified by HIV?

Feco-oral route

Vector-borne transmission

Direct contact (correct)

Airborne transmission

Which of the following viral shapes is described as spiral or cylindrical?

Helical (correct)

Complex

Polyhedral

Icosahedral

What characteristic do complex viruses lack?

Specific symmetry feats of common viral capsids Signup and view all the answers

Which kind of virus can withstand gastric acidity?

Icosahedral enveloped virus Signup and view all the answers

What is the primary purpose of inserted viral proteins, such as hemagglutinin?

Attachment and induction of protective immunity Signup and view all the answers

Which type of RNA is characterized as being (-) sense?

Helical enveloped virus Signup and view all the answers

What distinguishes an icosahedral enveloped virus from an icosahedral naked virus?

The existence of an outer envelope Signup and view all the answers

Which virus is classified as a negative strand RNA virus under the Baltimore Classification Group V?

Orthomyxoviridae Signup and view all the answers

What characteristic is unique to the Hepatitis D virus regarding its RNA?

It is a single-stranded RNA virus. Signup and view all the answers

What function do matrix proteins serve in viruses?

They may have enzymatic activities or biologic functions related to infection. Signup and view all the answers

Which of the following viral families contains viruses with segmented genomes?

Reoviridae Signup and view all the answers

What type of polymerase do negative strand RNA viruses typically bring for replication?

RNA-dependent polymerase Signup and view all the answers

What is the correct classification of HIV?

Group VII dsDNA (Retrovirus) Signup and view all the answers

Which of the following describes a syncytium?

A large multinucleated cell from viral infection Signup and view all the answers

During which phase of the viral growth curve is the number of virions limited?

Phase 4: Latent/Plateau phase Signup and view all the answers

Which of the following viruses is classified as a retrovirus?

HIV Signup and view all the answers

Which statement about virion numbers in a cell is true?

There is a cap on the number of virions in a cell. Signup and view all the answers

What is the primary role of hemagglutinin in influenza A infection?

It attaches to the host cell receptor. Signup and view all the answers

Which protein is responsible for attaching influenza A to its receptor site in red blood cells?

Hemagglutinin Signup and view all the answers

What kind of proteins do the simplest viruses typically contain?

Proteins sufficient to encode four proteins. Signup and view all the answers

What is the function of matrix proteins in a virus?

They interact with the nucleocapsid and envelope. Signup and view all the answers

Which of the following statements about viral proteins is correct?

Different viruses have unique receptor attachments. Signup and view all the answers

Which receptor does the spike protein of the virus primarily attach to?

ACE2 receptor Signup and view all the answers

What role do capsids play in the virus structure?

They provide structural symmetry. Signup and view all the answers

Which characteristic is NOT associated with the proteins encoded by the most complex viruses?

They solely function in viral genome replication. Signup and view all the answers

Which of the following represents a retrovirus?

HIV and HTLV Signup and view all the answers

What is the classification of the virus that exhibits single stranded negative strand RNA?

Group V Signup and view all the answers

What type of virus is characterized as double stranded RNA?

Reovirus Signup and view all the answers

Which of the following describes the abbreviation 'CPE'?

Cytopathic Effects Signup and view all the answers

Which group of viruses includes the hepatitis B virus?

dsDNA Signup and view all the answers

Which virus is associated with the family Orthomyxoviridae?

Flu virus Signup and view all the answers

Which of the following properties applies to a virion?

It is composed of nucleic acid and proteins. Signup and view all the answers

What is the primary characteristic of ssRNA (+) viruses?

They can be directly translated into proteins. Signup and view all the answers

Which classification includes viruses like SARS?

ssRNA (+) Signup and view all the answers

Which family does the rabies virus belong to?

Rhabdoviridae Signup and view all the answers

Study Notes

Capsid Structure and Types

A capsid is a protein coat that encloses the viral genome.
Three types of symmetry in capsid structures:
- Icosahedral (Cubic): Features 20 flat sides, commonly seen with DNA and (+) sense RNA viruses.
  - Can be naked (no envelope) or enveloped (surrounded by an envelope).
- Helical: Spiral or cylindrical shape, significant for enveloped (-) sense RNA viruses.
  - Includes naked helical viruses with coiled nucleocapsids.
- Complex: Lacks clear symmetrical features, examples include Poxvirus (dumbbell-shaped) and Rabies virus (bullet-shaped).

Viral Transmission

Modes of transmission include:
- Direct contact: Example: HIV transmission.
- Feco-oral route: Example: Poliovirus infection.

Viral Resistance and Immune Response

Different responses to environmental factors:
- Some viruses cannot withstand factors like heat and gastric acidity.
- Others can endure acidic environments.

Viral Proteins and Functions

Inserted viral proteins (peplomers) are crucial for:
- Attachment to host cells (e.g., hemagglutinin used by Influenza A).
- Induction of protective immunity (e.g., hemagglutinin for flu vaccines).
Structural proteins assist in:
- Attachment to host cell receptors.
- Providing integrity to the capsid.
- Interactions with matrix proteins between the nucleocapsid and envelope.

Spike Proteins

Spike proteins protrude from the viral surface/envelope and are vital for:
- Attachment to specific host receptors, such as ACE2 and TMPRSS2 in SARS-CoV.
Glycoproteins in spikes are essential in viral attachment and immune response.

Baltimore Classification of Viruses

Group classifications based on the type of nucleic acid:
- dsDNA: Double stranded DNA viruses.
- ssDNA: Single stranded DNA viruses.
- dsRNA: Double stranded RNA viruses (e.g., Reoviridae).
- ssRNA: Single stranded RNA viruses can be positive or negative sense.
- Retroviruses: Group of viruses that replicate through a reverse transcription process, such as HIV.

Viral Complexity

The simplest viruses contain enough RNA or DNA to encode four proteins, while more complex viruses can encode 100-200 proteins.

Syncytium Formation

Syncytium is a coalescent, multinucleated cell formed by the fusion of infected cells, often seen in viral infections.

Key Viral Examples

HIV: Classified as a retrovirus.
Influenza A: Utilizes hemagglutinin for host cell attachment.
Rabies virus: Demonstrates complex capsid structure.

Learning Objectives

Understand virion properties concerning their acellular nature and lack of metabolic processes.
Recognize the significance of the capsid and its symmetry in all viruses.
Appreciate how different viruses adapt to host environments and exploit host cellular machinery.

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Description

This quiz focuses on the structure and functions of the capsid, a protein coat that encloses the viral genome. It also explores transmission modes such as direct contact and the feco-oral route, along with the environmental factors affecting them. Test your understanding of these key virology concepts.