Virus Structure And Life Cycle

Question 1

Fill in this table.

Answer 1

Question 2

What four things can viruses infect?

Answer 2

1. Animals. 2. Plants. 3. Microbes. 4. Viruses.

Question 3

Viruses are host selective. True or false?

Answer 3

True.

Question 4

Define viral characteristics.

Answer 4

Genetic information contained within a protein coat, requiring a living cell in order to replicate.

Question 5

What three things does viral characteristics contain?

Answer 5

1. 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.

Question 6

What is the length of bacteria?

Answer 6

1000nm to 10,000nm.

Question 7

What is the size of viruses?

Answer 7

30nm to 100nm.

Question 8

What is the size of a poxvirus?

Answer 8

200nm to 400nm.

Question 9

What is the size of a filovirus?

Answer 9

80nm in diameter and 9000nm to 14,000nm long.

Question 10

What is the non-enveloped virus also referred to as?

Answer 10

The naked virus.

Question 11

In reference to a non-enveloped virus, what does its capsid offer to the virus itself?

Answer 11

Protection and interaction with host receptors for cell entry.

Question 12

Name three examples of a non-enveloped virus.

Answer 12

1. Norovirus. 2. Papillomavirus (warts). 3. Poliovirus.

Question 13

Label this diagram.

Answer 13

Question 14

Define viral envelope.

Answer 14

A lipid bilayer taken from their host.

Question 15

In reference to an enveloped virus, what three combinations of host cell does it consist of?

Answer 15

1. Plasma membrane. 2.Nuclear membrane. 3. Trans Golgi network.

Question 16

What are the spikes on an enveloped virus known as?

Answer 16

Carbohydrate-protein complexes.

Question 17

Name three examples of enveloped viruses.

Answer 17

1. Herpes virus. 2. Influenza. 3. Retroviruses.

Question 18

State four features of an icosahedral viral shape.

Answer 18

1. Spherical. 2. Limited amount of viral nucleic acid. 3. Has twenty equilateral triangular planes. 4. More capsomers means it’s more stable.

Question 19

Define two features of a helical viral shape.

Answer 19

1. Rod shaped so is flexible. 2. It contains large quantities of viral nucleic acid.

Question 20

How does size size affect the complexity of the genome? Name two examples.

Answer 20

The larger the virus, the more complex the genome; such as poxviruses and bacteriophages.

Question 21

State four general properties of the extracellular state in regards to viruses.

Answer 21

1. Minute particle (nm) - virion. 2. Nucleic acid and protein. 3. Metabolically inert. 4. Infectious potential which is measured in the periphery.

Question 22

State four general properties of the intracellular state in regards to viruses.

Answer 22

1. 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.

Question 23

Type A influenza can infect what?

Answer 23

Humans and animals.

Question 24

Type B influenza can infect what?

Answer 24

Humans.

Question 25

Type C influenza can cause what?

Answer 25

A mild respiratory infection, which is common. There is no vaccine.

Question 26

Label this diagram.

Answer 26

Question 27

What family does the influenza virion belong to?

Answer 27

Orthomyxoviridae.

Question 28

What is the diameter of the influenza virion?

Answer 28

80nm to 120nm.

Question 29

What are the five stages of viral lifecycle?

Answer 29

1. Attachment. 2. Uncoating. 3. Viral replication, transcription and translation. 4. Viral assembly and packaging. 5. Budding or exocytosis.

Question 30

Define attachment in regards to the viral lifecycle.

Answer 30

Viral receptors attach to the host cell, leading to viral uptake.

Question 31

Define uncoating in regards to the viral lifecycle.

Answer 31

Release of genetic information.

Question 32

Define viral replication, transcription and translation in regards to the viral lifecycle.

Answer 32

It hijacks the cell machinery and down regulates host replication.

Question 33

Define epidemic.

Answer 33

Outbreak in a certain population at a certain time, such as seasonal winter outbreaks.

Question 34

Define pandemic.

Answer 34

Outbreak in an entire country or the whole world.

Question 35

What does HA stand for and what is its percentage?

Answer 35

Haemagglutinin (80%).

Question 36

What does NA stand for and what is its percentage?

Answer 36

Neuraminidase (20%).

Question 37

What is the function of HA?

Answer 37

It is a transmembrane protein involved in binding to host receptors and fusion for viral entry.

Question 38

What is the function of NA?

Answer 38

It is a integral membrane protein involved in viral assembly and release of new virus particles.

Question 39

All H and N types spread efficiently in humans, apart from what three?

Answer 39

H5, H7 and H9.

Question 40

How many subtypes of HA are there?

Answer 40

16.

Question 41

How many subtypes of NA are there?

Answer 41

9.

Question 42

Define antigenic drift in reference to viral reassortment.

Answer 42

The sequence changes in H and N proteins, it naturally occurs during seasonal outbreaks and it affects Influenza A and B.

Question 43

Define antigenic shift in reference to viral reassortment.

Answer 43

It is responsible for pandemics, there is no previous immune response and it only affects Influenza A.

Question 44

What three inactivated viruses does the flu vaccine contain?

Answer 44

2x A and 1x B/.

Question 45

What are viruses essential for?

Answer 45

Maintaining ecosystems.

Question 46

Who removed bacteriophages from sea water? What was their hypothesis?

Answer 46

Gunnar Bratbak (1990) expected to see an increase in bacterial life.

Question 47

What are the five stages of a bacteriophage lifecycle?

Answer 47

1. Attachment. 2. Biosynthesis - replication of viral genome. 3. Expression of viral phage genes. 4. Assembly. 5. Release.

Question 48

How long does the lifecycle of a T4 bacteriophage take? How many new phages does this create?

Answer 48

It takes 30 minutes and produces around 150 new phages.

Question 49

What are four limitations of bacteriophage therapeutics?

Answer 49

1. 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.