Viral Structures and Components

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Describe the structure of viruses.

Viruses contain either DNA or RNA and may be double stranded, single stranded, linear or circular. They have a protein capsid made up of repeated subunits and some viruses have an envelope consisting of a lipid bilayer derived from the host cell. Viruses can have icosahedral or helical symmetry.

What are the characteristics of viruses?

Viruses are very small, non-cellular microbes that are difficult to visualize without special techniques like electron microscopy. They are obligate intracellular parasites, meaning they depend on host cells for metabolism and reproduction. Their genetic material is in the form of DNA or RNA, and they replicate by hijacking the host cell's machinery. Viruses undergo rapid evolution due to high mutation rates.

What is the function of the protein capsid in viruses?

The protein capsid protects the viral genome from the environment and delivers it to the host cell.

What is an envelope in viruses?

In some viruses, the capsid is enveloped. The envelope consists of a lipid bilayer derived from the host cell and contains viral proteins. Signup and view all the answers

What is icosahedral symmetry in viruses?

Icosahedral symmetry refers to the arrangement of repeated subunits in equilateral triangles, giving viruses a symmetrical shape. Signup and view all the answers

What is helical symmetry in viruses?

Helical symmetry refers to viruses being made up of a single repeated unit that forms a helical shape. Signup and view all the answers

Why are viruses difficult to target without harming host cells?

Viruses are obligate intracellular parasites and lack the cellular machinery necessary for independent metabolism and reproduction. Targeting viral replication without interfering with normal cellular functions is a complex task. Signup and view all the answers

How do viruses replicate?

Viruses replicate by hijacking the host cell's machinery to reproduce their genetic material and assemble new viral particles. Signup and view all the answers

What is the role of the host cell in virus assembly?

The host cell produces the virus components, which are then assembled into progeny virus particles. Signup and view all the answers

Why can viruses undergo rapid evolution?

Viruses have high mutation rates and short generation times, allowing for rapid evolution. Signup and view all the answers

List three ways in which rapid evolution can contribute to the emergence of drug-resistant viral strains.

<ol> <li>Constant monitoring and adaptation of therapeutic strategies, 2) Establishment of latent infections, 3) Reactivation leading to recurrent disease.</li> </ol> Signup and view all the answers

Explain the process of viral entry into the host through the respiratory tract.

Viral entry into the host through the respiratory tract can occur through inhalation and touch. Signup and view all the answers

What are the four different routes of viral entry into the host?

<ol> <li>Respiratory tract, 2) Gastrointestinal tract, 3) Urogenitary tract, 4) Blood</li> </ol> Signup and view all the answers

Describe the process of viral spread within the host.

Viral spread within the host can be localized at the site of infection or can occur through mechanisms such as neural spread and hematogenous spread. Signup and view all the answers

How does the host respond to a viral infection?

The host responds to a viral infection through recognition of viral invasion, activation of innate immunity, cytotoxic T cell response, production of neutralizing antibodies, and development of long-term immunity through memory cells. Signup and view all the answers

What are two methods for diagnosing viral infections?

The virus can be detected through PCR or antigen tests, and the host response can be detected through serology testing for antibodies IgM and IgG. Signup and view all the answers

How can viral infections be controlled?

Viral infections can be controlled through the use of personal protective equipment (PPE), isolation and quarantine measures, passive immunization with antibodies harvested from donors or tissue culture. Signup and view all the answers

Why is constant monitoring and adaptation of therapeutic strategies necessary in dealing with drug-resistant viral strains?

Constant monitoring and adaptation of therapeutic strategies is necessary in dealing with drug-resistant viral strains because these strains can emerge due to rapid evolution, and new therapeutic strategies need to be developed to effectively combat them. Signup and view all the answers

What is the role of the immune system in responding to a viral infection?

The immune system plays a role in recognizing viral invasion, activating innate immunity, eliminating infected cells through cytotoxic T cell response, producing neutralizing antibodies, and developing long-term immunity through memory cells. Signup and view all the answers

What are the characteristics of viruses and what makes it challenging to deal with them?

1)Very small, non cellular microbe (10-200 nm)- difficult to visualise them, requires special techniques like electron microscopy. 2) Obligate intracellular parasite- Viruses lack the cellular machinery necessary for independent metabolism and reproduction. They cannot carry out essential life processes without the host cell's machinery. This obligate dependence on host cells makes it challenging to target viruses without harming host cells. 3) Genetic material is in the form of DNA or RNA which requires varied strategies for diagnosis, treatment and prevention. 4) Replication Mechanism: Viruses replicate by hijacking the host cell's machinery to reproduce their genetic material and assemble new viral particles. Targeting viral replication without interfering with normal cellular functions is a complex task. 5) Assembly- The virus components produced by the host cell are assembled into the progeny virus particles. 6) Rapid Evolution: Viruses can undergo rapid evolution due to their high mutation rates and short generation times. This rapid evolution can contribute to the emergence of drug-resistant strains, requiring constant monitoring and adaptation of therapeutic strategies. 7) Latency and Persistence: Some viruses can establish latent infections, where they remain in the host in a dormant state, potentially reactivating later. Latency makes it difficult to completely eliminate certain viral infections, and reactivation can lead to recurrent disease. Signup and view all the answers

How does the viral pathogen infect and grow within the host?

Viral growth cycle:- 1)Attachment - interact with specific receptors in target cell 2) Entry - endocytosis 3) Uncoating - viral nucleic acid released from capsid 4) Nucleic acid and protein synthesis – host ribosomes used (host polymerases may also be used) to produce new viral proteins 5) Assembly - nucleic acids and proteins packaged together 6) Release - Budding - virus released with envelope derived from host cell membrane, doesn’t kill cell - Lysis - viruses accumulates until cell bursts, killing cell Signup and view all the answers

What are the entry pathways for the virus into the host?

Viral entry into the host:- <ol> <li>Respiratory tract- Inhalation and touch, sexual (upper respiratory)</li> <li>Gastrointestinal tract- Ingestion and inhalation</li> <li>Urogenitary tract- Sexual transmission</li> <li>Blood- Vertical (child birth), needles, products, insect vector</li> </ol> Signup and view all the answers

What are the various ways in which the virus causes damage to the host cell?

<ol> <li>Cell lysis</li> <li>Cell-cell fusion</li> <li>Inhibition of host cell transcription and translation which would alter the functioning of the host cell.</li> <li>Alteration of the host cell cycle causing proliferation and potentially cancer.</li> </ol> Signup and view all the answers

What is the host's immediate response to the viral infection?

The host would be induced into apoptosis or programmed cell death as a response to the viral infection. It would also attempt the lysis of the infected cells via the immune cells. It would also employ inflammatory factors to stimulate the antibodies to fight against the viral pathogens. Signup and view all the answers