Virology Lecture 4: Attachment and Entry

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What is the function of a class II fusion protein during viral entry?

Mediates virus attachment to the host cell

Induces conformational changes that lead to membrane fusion or penetration (correct)

Binds to specific receptors on the host cell

Facilitates viral genome replication inside the cell

In the infectious cycle, which type of cell is the only one capable of taking up a virus particle and replicating it?

Permissive cell

Non-functional cell

Resistant cell

Susceptible cell (correct)

What is the primary role of a class I fusion protein in viral entry?

Facilitates assembly and release of new virions

Mediates fusion of viral and cellular membranes (correct)

Stimulates viral mRNA production and translation

Attaches to specific receptors on the host cell surface

Why are viruses considered obligate intracellular parasites?

Because they are too large to diffuse across plasma membranes Signup and view all the answers

During viral attachment, what is the significance of step 1 - adhering to the cell surface?

It is mediated by random collisions and electrostatic interactions Signup and view all the answers

What differentiates a permissive cell from a susceptible cell in terms of viral replication?

Permissive cells may or may not be susceptible to viruses Signup and view all the answers

What is the specific receptor in the endosome membrane that the viral fusion protein binds to?

Niemann-Pick C1 protein Signup and view all the answers

Which type of fusion protein requires proteolytic cleavage to activate for fusion?

Class I fusion proteins Signup and view all the answers

How are genomes released from non-enveloped viruses like Adenovirus?

Uncoating at the nuclear pore complex Signup and view all the answers

Which virus requires a low pH environment for fusion to occur?

Influenza virus Signup and view all the answers

What allows some viruses to breach the strong cell wall of bacterial cells during infection?

Exploitation of specialized structures on the bacterial surface Signup and view all the answers

Why do plant viruses require assistance from external trauma for entry into plant cells?

To overcome the rigid cell walls of plant cells Signup and view all the answers

What is the main mechanism of entry for influenza virus into host cells?

Membrane fusion Signup and view all the answers

Which type of fusion protein is mostly α-helical and forms trimers?

Class I fusion proteins Signup and view all the answers

In acid-catalyzed membrane fusion, what does the hemagglutinin (HA) protein of influenza virus undergo?

Conformational rearrangement Signup and view all the answers

Which type of fusion proteins are mostly β-sheet and form dimers parallel to the membrane?

Class II fusion proteins Signup and view all the answers

Which type of sialic acid is preferentially bound by human strains of influenza viruses?

N-acetylneuraminic acid Signup and view all the answers

What is the key event that mediates the fusion of viral and host cell membranes during viral entry?