Virus Structure and Composition

Questions and Answers

What term refers to a virus that is made up solely of nucleocapsid?

Segmented virus

Complex virus

Naked virus (correct)

Enveloped virus

Which of the following describes a characteristic of all animal RNA viruses?

They are single-stranded. (correct)

They can possess an envelope.

They are circular.

They are double-stranded.

What does the term nucleocapsid refer to?

The capsid surrounding the viral envelope

The nucleic acid combined with viral lipids

The enzymes and glycoproteins in a virus

The nucleic acid and the protein shell (correct)

Which virus is an example of an enveloped virus?

HIV Signup and view all the answers

How can one analyze the sequence or composition of nucleotides in viral nucleic acids?

Through restriction nucleases. Signup and view all the answers

Which of the following statements is true regarding the nucleic acids of viruses?

Viral nucleic acids can be segmented or non-segmented. Signup and view all the answers

What is the composition of the viral capsid primarily made up of?

Viral proteins Signup and view all the answers

In comparison to bacterial structures, what main structural feature differentiates viruses?

Lack of cellular structure Signup and view all the answers

Which of the following best describes viral glycoproteins?

They form part of the viral envelope. Signup and view all the answers

Which statement accurately describes the capsid's function related to immune response?

It confers antigenicity, allowing specific binding to immune components. Signup and view all the answers

What are capsomeres?

Individual protein subunits of a viral capsid. Signup and view all the answers

How does the viral envelope acquire its components?

It incorporates lipids coded for by the host cell. Signup and view all the answers

What structural characteristic differentiates poxviruses from parvoviruses?

Poxviruses range from 200-300 nm, while parvoviruses are 20-25 nm. Signup and view all the answers

Which of the following is a function of the viral envelope?

It facilitates attachment to host cells. Signup and view all the answers

Which viral proteins are essential for host cell attachment and release of new viral particles?

Neuraminidase and haemagglutinin. Signup and view all the answers

What term describes the smallest measurement used for viruses?

Nanometers (nm) Signup and view all the answers

Which of the following is NOT a function of the capsid?

Facilitates the replication of viral proteins. Signup and view all the answers

Which viruses are typically characterized by a more elaborate tailed structure?

Bacterial viruses. Signup and view all the answers

Which category of virus morphology does NOT include a nucleocapsid symmetry?

Complex viruses Signup and view all the answers

What is the effect of heating viruses at temperatures of 50°-60°C for 30 minutes?

Their infectivity is generally destroyed Signup and view all the answers

Which statement accurately describes the stability of enveloped viruses?

Enveloped viruses lose infectivity after prolonged freezing Signup and view all the answers

What is a common stabilization method for certain viruses during vaccine preparation?

Utilizing specific salts Signup and view all the answers

At what pH range do most viruses exhibit stability?

Between pH 5 and 9 Signup and view all the answers

What happens to icosahedral naked viruses at 37°C according to the stability characteristics provided?

They show little to no loss in infectivity Signup and view all the answers

What is the effect of storage at sub-zero temperatures on most viruses?

Some can withstand lyophilization and remain viable Signup and view all the answers

Which salt is known to stabilize herpes viruses?

Na2SO4 Signup and view all the answers

What is a notable characteristic of enveloped viruses in relation to thawing?

They are very sensitive to freezing and thawing cycles Signup and view all the answers

What is the primary target tissue for SARS-CoV-2 infection?

Alveolar epithelial cells Signup and view all the answers

How does SARS-CoV-2 enter the host cell?

Through receptor binding and membrane fusion Signup and view all the answers

What type of virus is SARS-CoV-2 classified as?

Enveloped positive-sense single-stranded RNA virus Signup and view all the answers

Which preventive measure is NOT a pharmaceutical intervention for COVID-19?

Hand hygiene Signup and view all the answers

What is one of the indirect transmission methods of SARS-CoV-2?

Touching contaminated surfaces followed by facial contact Signup and view all the answers

Which of the following describes a step in the mechanism of infection by SARS-CoV-2?

Viral RNA is released and translated in the host cell cytoplasm Signup and view all the answers

What shape has a regular icosahedron?

20 faces, each shaped like an equilateral triangle Signup and view all the answers

What type of virus structure is associated specifically with RNA viruses?

Helical structure Signup and view all the answers

Which characteristic defines a virus classified as complex?

It does not fit clearly into icosahedral or helical classification. Signup and view all the answers

What is a defining feature of helical animal viruses?

They are always surrounded by a viral envelope. Signup and view all the answers

What is the role of the capsid in viruses?

To package the virus's nucleic acid. Signup and view all the answers

Which geometric symmetry is NOT listed among the precise symmetries for viruses?

Tetrahedron Signup and view all the answers

What type of virus structure can be either naked or enveloped?

Both icosahedral and helical viruses Signup and view all the answers

What does the arrangements of the repeating subunit in the capsid determine?

The overall shape of the virus particle Signup and view all the answers

Which option best describes the appearance of complex viruses?

Irregular configurations unaligned with simple symmetries Signup and view all the answers

Which structure is typically associated with viruses that do not have a rigid form?

Complex Signup and view all the answers

Study Notes

Virus Structure

Viruses consist of a capsid (an outer protein shell) and nucleic acid, forming a nucleocapsid.
Additional membrane, called an envelope, can be present: enveloped viruses (e.g., SARS-COV-2, Ebola) vs. naked viruses (e.g., Human Papillomavirus).

Chemical Composition of Viruses

Components include:
- Viral nucleic acid (genome with genetic information)
- Viral protein (capsid and enzymes)
- Viral lipids (from the envelope)
- Viral glycoproteins (projections on the envelope).

Nucleic Acid

Characteristics of viral nucleic acid:
- Can be single/double-stranded, circular/linear, segmented/non-segmented, or positive/negative polarity.
Animal RNA viruses are typically single-stranded; DNA viruses usually double-stranded.

Structure and Functions of Capsid

Capsid made of polypeptides and capsomers (protein subunits).
Functions of the capsid:
- Protects nucleic acid
- Facilitates cell attachment
- Provides structural symmetry
- Confers antigenicity.

Viral Enzymes

Key enzymes include polymerase, integrase, and reverse transcriptase.

Viral Lipids and Glycoproteins

Envelope is acquired during viral replication; consists of a lipid bilayer with glycoproteins.
Glycoproteins have functions in virus attachment (e.g., neuraminidase, haemagglutinin).

General Morphology of Virion

Virus particles range from 20-300 nm in size; smallest compared to other microorganisms.
Common shapes include icosahedral, helical, and complex configurations.

Viral Morphologies

Categorized into five groups based on morphology and symmetry:
- Naked icosahedral
- Enveloped icosahedral
- Naked helical
- Enveloped helical
- Complex viruses (e.g., HIV, Poxvirus).

Stability of Viruses

Naked icosahedral viruses stable at 37°C, while enveloped viruses are heat-labile.
Viral infectivity typically destroyed at 50-60°C for 30 minutes; can be preserved by sub-zero storage.

Stabilization by Salts

Certain salts stabilize viruses; mechanisms largely unknown.
Important for vaccine preparation efficacy.

SARS-CoV-2 Characteristics

Enveloped, positive-sense, single-stranded RNA virus, part of the Betacoronavirus genus.
Structural proteins: nucleocapsid, membrane, envelope, and spike proteins.

Transmission Modes of SARS-CoV-2

Direct (respiratory droplets), indirect (contaminated surfaces), and aerosol (airborne particles) transmission.

Infection Mechanism

Primary targets are respiratory tract cells; replication occurs in host cell cytoplasm.
Viral assembly leads to cell damage and inflammation upon virion release.

Prevention Strategies

Vaccination methods include mRNA (e.g., Pfizer-BioNTech), viral vector (e.g., AstraZeneca), and inactivated virus (e.g., Sinovac).
Non-pharmaceutical measures: masks, hygiene, physical distancing, and ventilation.

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Description

Explore the intricate details of virus structure and chemical composition. This quiz covers the components of viruses, including their capsids, nucleic acids, and how these elements interact within enveloped and naked viruses. Test your understanding of viral characteristics and functions related to their structural components.