Virus - Structure/Function

Question 1

How much of our genome is viral?

Answer 1

8% is endogenous retroviruses due to ancestral infection.

Question 2

Virus

Answer 2

Simple, miniscule, infectious, obligate intracellular parasite comprised of genetic material surrounding by a capsid and/or enveloped derived from host cell.

Question 3

What is a virus composed of?

Answer 3

Nucleic acids and proteins

Question 4

What is the base mechanism of viruses?

Answer 4

Hijack metabolic functions of the cell and produce their own protein viruses.

Question 5

Why are viruses host obligates?

Answer 5

They have to hijack machinery.

Question 6

iWhat genetic material do viruses contain?

Answer 6

ssDNA/RNA or dsDNA/RNA

Question 7

What is an example of a small viral genome?

Answer 7

Influenza virus has 11 genes

Question 8

What is the average size of viruses?

Answer 8

1-1000 micrometres.

Question 9

What are examples of size scale of viruses?

Answer 9

Poliovirus same as ribosome
Rhiovirus 20-30 nm in diametre
Bacteriophage M52 24nm in size
Mimivirus 750nm
Pandoravirus 2.9MB genome

Question 10

What is the difference between virus and virion?

Answer 10

Intracellular and extracellular for replicaiton and transmission respectively.

Question 11

How are viral structures determined?

Answer 11

Cry-electron microscopy
Electron microscopy
X-Ray Crystallography
Nuclear Magnetic Resonance Spectroscopy

Question 12

What is the structre of the viron?

Answer 12

Centre nucleic acid surrounded by capsomers forming capsid, together the nucleocapsids

Question 13

What determines virus shape?

Answer 13

Arrangement of capsomers

Question 14

What are the two types of capsomers?

Answer 14

Pentamers-5 protein subunits
Hexamers -6 protein subunits

Question 15

What are the three categories of capsid shape?

Answer 15

Helical
Polyhedral
Binal

Question 16

Helical Capsid

Answer 16

Where capsomers bond in a spiral fashion(Tobacco mosaic virus)

Question 17

Polyhedral Capsid

Answer 17

This is a icosahedron carrying 20 faces and 12 corners(Adenovirus)

Question 18

Binal Capsid

Answer 18

Irregular shapes or complex structures(monkeypox)

Question 19

What is the function of the capsid?

Answer 19

Protects nucleic acids from enzmatic digestion, allows host cell binding thus host penetration.

Question 20

What is an example of viral receptor for penetration?

Answer 20

ACE2

Question 21

How does SARS-CoV-2 infect?

Answer 21

Spike proteins with ACE2 fuse with host membrane.

Question 22

Spike protein

Answer 22

Large glycoprotein with NTD, CTD and receptor-binding domain

Question 23

What happens when spike protein binds?

Answer 23

CC expose a fusion peptide interacting with host membrane to initate fusion.

Question 24

What are the two types of virus?

Answer 24

Enveloped
Naked

Question 25

Naked Viruses

Answer 25

These are absent of a membrane being more envrionmentally stable surviving wider conditions

Question 26

Enveloped Viruses

Answer 26

These are viruses that have a lipid membrane surrounding the nucleocapsid derived from the host cell membrane

Question 27

What is an example of an enveloped virion?

Answer 27

Cornoavirus

Question 28

How do hosts differ in viral infection?

Answer 28

Bacteria- BP T4 Protozoa Trichomonas Algae by Phycodnaviridae Fungi by mycoviruses Plants like TMV Animals like Avian Influenza Viruses by Virophages

Question 29

What can Trichomonas infect?

Answer 29

Protozoa and cant infect vertebrates but CAN be sensed by them.

Question 30

What can Phycodnaviridae infect?

Answer 30

Algae and humans

Question 31

What is the structure of bacteriophages?

Answer 31

Icosahedral head composed of 12 pentameric capsomers and 20 hexameric capsomers

Question 32

What is the genetic structure of Bacteriophage?

Answer 32

Linear dsDNA about 169KB long within the head connected to the tail by a neck.

Question 33

What is the bacteriophage tail composed of?

Answer 33

Baseplate, central tube and a sheat for attachment/penetration

Question 34

Why is the bacteriophage tube important?

Answer 34

Delivery portion of the viral genome into bacteria

Question 35

What is the lytic replication cycle of bacteriophages?

Answer 35

Adhesion Penetration Replicaiton Maturation Release Reinfection

Question 36

What are the alternate bacteriophage life cycles?

Answer 36

Temperate and lysogenic phages

Question 37

Temperate Phasge

Answer 37

These integrate into host chromosomes, producing repressor genes blocking lytic genes.

Question 38

How have phages been used in biomedicine?

Answer 38

Bacteria resistant to antibiotics like listeria destroying listeria