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19 Cards in this Set

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How small is a virus?

20-350 nm


capable of fitting through a 0.25 microm filter

What are virions and their properties?

Virions are small viral particles that are encoded by the viral genome. They are the inert carriers of the viral genome. They are made and assembled within the host cell. The do not divide or grow.

What are the functions of a virion?

1. transfer of viral genome between host cells.


2. protect the genome in inhospitable conditions.

Why do virus need viral envelopes?

virus need enveloped to surround the virions during budding process.

Describe the process of budding.

After all virions are assembled. The virions move towards the host cell membrane, which contains envelopes. As the virions exit the cell, the virions are covered by envelopes from the host cell membrane.

What are the two types of virion envelopes?

1. Glycoproteins


- that form spikes




2. Matrix proteins


- there is an extra layer on the inside of the envelope, which provides rigidity and a helical shape

What are naked viruses?

Naked viruses are viruses that do not have an envelope protecting the virion. This makes it hydrophilic. The virions are protected by an organic solvent.

What are the environmental stress of an enveloped virus? Due to these environmental stress, what are the virus' limitations?

Environmenal stress from:


- acid


- heat


- dessication


- detergent




Limitations:


- most be in moist conditions


- transmitted via large droplets


- cannot survive in gastrointestinal tract


- protected from immune system (due to envelope)

How is naked virus different to an envelope stress?

Naked envelopes can:


- withstand heat, dessication and acid


- thus can live in gastrointestinal tract


- spread easily


- trigger an immune response (no envelope)

What are the two virus shapes?

1. Spherical




2. Helical

How is the helical shape of a virus formed?

RNA self-assemble into a cylindrical nucleocapsid structure (hollow tube). RNA virus form a spiral within the hollow tube. Each capsomer is made up of one single protein.




ALL animal helical viruses are enveloped by a lipid bilayer.

How many faucets and vertical corners does a icosahedron virus shape have?

20 faucets


12 vertical corners

How many polymerases are there involved in the replication of viruses? List them.

4 polymerases




1. RNA dependent RNA pol


2. RNA dependent DNA pol (reverse transcriptase)


3. DNA dependent DNA pol


4. DNA dependent RNA pol (not used in viral replication)

What are the methods of viral transmission?

1. Skin wounds/openings


2. mucosal surfaces e.g. eyes, mouth, nose


3. Blood to Blood e.g. sharing syringes, blood transfusion


4. Vertical Transmission e.g. mother to baby

What is the result of high levels antigen-antibody complexes in the body?

Kidney disease

What is the role of cytotoxic T lymphocytes (CTL)?

CTL leads to lysis of infected cells and damage to the organ.

What is CPE?

CPE = cytopathic effect


changes to the host cells caused by viral replication.




e.g.


- cell lysis


- sycntia = fusion of cells to form multi-nucleated cells


- inclusion bodies = aggregation of virions





What are the characteristics of an acute infection?

Fast death and fast recovery

What are the characteristics of a persisitent infection?

Infection may be asymptotic, symptoms may not be present during infectious period. Can have sudden death. Reactivation of virus may cause secondary infection. e.g. Herpes