Virus Structure And Life Cycle Flashcards
Fill in this table.
What four things can viruses infect?
- Animals. 2. Plants. 3. Microbes. 4. Viruses.
Viruses are host selective. True or false?
True.
Define viral characteristics.
Genetic information contained within a protein coat, requiring a living cell in order to replicate.
What three things does viral characteristics contain?
- Genetic information in the form of RNA or DNA. 2. A protein capsid composed of capsomeres (for stability). 3. A receptor binding protein to enable cell entry.
What is the length of bacteria?
1000nm to 10,000nm.
What is the size of viruses?
30nm to 100nm.
What is the size of a poxvirus?
200nm to 400nm.
What is the size of a filovirus?
80nm in diameter and 9000nm to 14,000nm long.
What is the non-enveloped virus also referred to as?
The naked virus.
In reference to a non-enveloped virus, what does its capsid offer to the virus itself?
Protection and interaction with host receptors for cell entry.
Name three examples of a non-enveloped virus.
- Norovirus. 2. Papillomavirus (warts). 3. Poliovirus.
Label this diagram.
Define viral envelope.
A lipid bilayer taken from their host.
In reference to an enveloped virus, what three combinations of host cell does it consist of?
- Plasma membrane. 2.Nuclear membrane. 3. Trans Golgi network.
What are the spikes on an enveloped virus known as?
Carbohydrate-protein complexes.
Name three examples of enveloped viruses.
- Herpes virus. 2. Influenza. 3. Retroviruses.
State four features of an icosahedral viral shape.
- Spherical. 2. Limited amount of viral nucleic acid. 3. Has twenty equilateral triangular planes. 4. More capsomers means it’s more stable.
Define two features of a helical viral shape.
- Rod shaped so is flexible. 2. It contains large quantities of viral nucleic acid.
How does size size affect the complexity of the genome? Name two examples.
The larger the virus, the more complex the genome; such as poxviruses and bacteriophages.
State four general properties of the extracellular state in regards to viruses.
- Minute particle (nm) - virion. 2. Nucleic acid and protein. 3. Metabolically inert. 4. Infectious potential which is measured in the periphery.
State four general properties of the intracellular state in regards to viruses.
- Virus replication occurs. 2. Produces new copies of the viral genome using host machinery and viral factories. 3. Virus coat is snythesised. 4. Viral assembly occurs.
Type A influenza can infect what?
Humans and animals.
Type B influenza can infect what?
Humans.
Type C influenza can cause what?
A mild respiratory infection, which is common. There is no vaccine.
Label this diagram.
What family does the influenza virion belong to?
Orthomyxoviridae.
What is the diameter of the influenza virion?
80nm to 120nm.
What are the five stages of viral lifecycle?
- Attachment. 2. Uncoating. 3. Viral replication, transcription and translation. 4. Viral assembly and packaging. 5. Budding or exocytosis.
Define attachment in regards to the viral lifecycle.
Viral receptors attach to the host cell, leading to viral uptake.
Define uncoating in regards to the viral lifecycle.
Release of genetic information.
Define viral replication, transcription and translation in regards to the viral lifecycle.
It hijacks the cell machinery and down regulates host replication.
Define epidemic.
Outbreak in a certain population at a certain time, such as seasonal winter outbreaks.
Define pandemic.
Outbreak in an entire country or the whole world.
What does HA stand for and what is its percentage?
Haemagglutinin (80%).
What does NA stand for and what is its percentage?
Neuraminidase (20%).
What is the function of HA?
It is a transmembrane protein involved in binding to host receptors and fusion for viral entry.
What is the function of NA?
It is a integral membrane protein involved in viral assembly and release of new virus particles.
All H and N types spread efficiently in humans, apart from what three?
H5, H7 and H9.
How many subtypes of HA are there?
16.
How many subtypes of NA are there?
9.
Define antigenic drift in reference to viral reassortment.
The sequence changes in H and N proteins, it naturally occurs during seasonal outbreaks and it affects Influenza A and B.
Define antigenic shift in reference to viral reassortment.
It is responsible for pandemics, there is no previous immune response and it only affects Influenza A.
What three inactivated viruses does the flu vaccine contain?
2x A and 1x B/.
What are viruses essential for?
Maintaining ecosystems.
Who removed bacteriophages from sea water? What was their hypothesis?
Gunnar Bratbak (1990) expected to see an increase in bacterial life.
What are the five stages of a bacteriophage lifecycle?
- Attachment. 2. Biosynthesis - replication of viral genome. 3. Expression of viral phage genes. 4. Assembly. 5. Release.
How long does the lifecycle of a T4 bacteriophage take? How many new phages does this create?
It takes 30 minutes and produces around 150 new phages.
What are four limitations of bacteriophage therapeutics?
- Combination can cause mild fever to death of the patient. 2. Have a narrow host range. 3. Humans immune system destroys the bacteriophage. 4. Some bacteria are resistant to infection.
