Structure of Viruses Flashcards

1
Q

What are viruses

A

Must have a host to replicate
Exploit host cell metabolic processes
Contain nucleic acid genetic material
V. small - some have 5 genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

General structure

A

Genome + protein subunits

Virion= extracellular form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Symmetry

A

Nucleocapsids are always symmetrical
Either:
Spherical (Icosahedral symmetry) - eg human papillomavirus
Rod (Helical symmetry) - eg tobacco mosaic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Complex viruses

A

Example - bacteriophage T4
Icosahedral head
Helical tail
Number of tail fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Genomes

A

Most viruses have RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Baltimore Classification

A

Viruses are classified according to the nature of their genetic material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Virus Envelope

A

Some viruses acquire a lipid bilayer “envelope” as they bus from the surface of cells
Often the envelope contains virus proteins important for infecting other cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Virus enzymes

A

E.g some bacteriophage contain lysosome needed for entry of their DNA
E.g Influenza viruses carry neuraminidase to allow release from infected cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Other virus enzymes

A

RNA viruses always have their own replicase

Retroviruses carry their own replicase, “reverse transcriptase” that copies RNA into DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Virus replication

A

One cellular process that ALL viruses require = protein translation on the ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Virus replication

A
  1. Attachment (adsorption)
  2. Penetration (injection)
  3. Synthesis (of nucleic acid and protein)
  4. Assembly and packaging
  5. Release (lysis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Attachment and entry - Animal cells

A

Viruses bind to specific receptor
Viruses enter animal cells by Endocytosis or Membrane fusion
Host cell specificity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Virus entry cont.

A

The virus envelope fuses with the plasma membrane of the cell
The virus RNA is released into the cytoplasm of the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Production of viral nucleic acid

A
  • Production of some virus proteins
  • requiring viral mRNA
  • then genome is replicated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Forming the virus

A

Some virus proteins form the virus coat
The virus coat forms around the nucleic acid
Virus capsids self assemble

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Release of the virus

A

Viruses get out of cells by

  • budding through cell membrane (virus then acquires envelope)
  • Cell lysis
  • Cell death
17
Q

Subviral entities

A

Helper or defective viruses
-e.g. bacteriophage P4 of E.coli
P4 does not encode a capsid protein and relies on phage P2 to provide its capsid

18
Q

Subviral entities

A

Helper or defective viruses (II)

-e.g. adeno-associated virus (satellite virus) AAV need adenovirus (unrelated virus) to replicate

19
Q

Subviral entities

A

Viroids are found in plants and cause disease
They are small circular RNA molecules that do not have a protein coat
The special structure of viroid RNA makes it stable inside and outside of cells
Viroids contain NO protein-coding genes

20
Q

Subviral entities

A

Prions consist entirely of protein
No RNA or DNA but they are infectious!
-cause BSE (Mad cow disease)
-cause Creutzfeldt-Jakob disease (CJD)