Week 6 Flashcards
(22 cards)
What is the definition of a virus?
obligate intracellular parasite that cannot carry out any metabolic pathways on its own and can only multiply inside host cells.
What are the key characteristics of viruses?
lack typical cellular structures, do not have organelles, and rely completely on the host cell to replicate and reproduce.
What is a virion?
a complete virus particle consisting of a capsid (protein coat) and a nucleic acid core (DNA or RNA).
What are the two main types of viral genomes?
DNA and RNA
What is the role of the capsid in viruses?
the protein coat that protects the viral genome and ensures the virus can attach to host cells and be transmitted to other hosts.
What are the two main types of capsid symmetry?
Icosahedral symmetry (spherical) and helical symmetry (rod-shaped).
What is the difference between enveloped and non-enveloped viruses?
Enveloped viruses have a lipid bilayer membrane derived from the host cell,
non-enveloped viruses lack this outer membrane and only have the capsid surrounding the nucleic acid.
What is the importance of viral glycoproteins on the viral envelope?
Viral glycoproteins, often called spikes, are involved in the attachment of the virus to specific receptors on host cells, facilitating entry.
How do naked (non-enveloped) viruses enter host cells?
enter host cells via endocytosis, where the host cell engulfs the virus and internalizes it into a vesicle.
How do enveloped viruses enter host cells?
enter host cells through membrane fusion, where the viral envelope fuses with the host cell membrane, releasing the viral nucleocapsid into the cytoplasm.
What determines the host range of a virus?
determined by the specific receptors on the host cell membrane that the viral spike proteins (glycoproteins) can bind to.
What is viral tropism?
the specificity of a virus for particular cell types, tissues, or organs, dictated by the interaction between the viral surface proteins and host cell receptors.
What is uncoating in the viral replication cycle?
the viral capsid is removed, releasing the viral genome into the host cell’s cytoplasm for replication and transcription.
How do RNA viruses replicate?
using the host’s machinery to synthesize viral proteins and replicate the RNA genome.
Positive-sense RNA serves directly as mRNA for translation, while negative-sense RNA must be transcribed into positive-sense RNA before translation.
What is the role of viral RNA polymerase in RNA virus replication?
crucial for replicating the viral RNA genome, especially for negative-sense RNA viruses, which require it to transcribe RNA into complementary strands.
What is the process of release in the viral life cycle?
Naked viruses are typically released by lysis, destroying the host cell
enveloped viruses are released by budding, taking part of the host’s membrane as their envelope.
What is budding in enveloped viruses?
enveloped viruses acquire their envelope by taking a portion of the host cell’s membrane, and new viral particles are released without immediately killing the host cell.
What determines virus classification?
genome type (DNA or RNA), capsid symmetry, presence or absence of an envelope, and host range.
What is the structure of Tobacco Mosaic Virus (TMV)?
a helical capsid structure with a RNA genome, causing diseases in plants by disrupting normal cell function.
How is a virus named?
based on their family, genus, and species
What is the role of ICAM-1 in Rhinovirus infection?
a receptor on host cells that major-group rhinoviruses bind to, allowing entry and causing the common cold.
What is viral specificity?
the ability of viruses to infect only certain cell types or host species, due to the interaction between viral proteins and host cell receptors.
