Viruses

Question 1

What are viruses

Answer 1

Acellular microorganisms that cannon survive without a hose: no metabolic activities of their own.
Rely completely on the bio synthetic machinery of infected cell to multiply.
Infects all types of cells.
Most abundant biological entities on earth

Question 2

What are the 2 parts viruses consist of, and the occasional third.

Answer 2

Genetic material - either ss or do RNA or DNA
Capsid - a protein coat that surrounds and protects the genetic material
Envelope of lipids (some cases) - surrounds the protein coat when they are outside a cell

Question 3

What is a viral capsid and what is it made of

Answer 3

Protein surrounds protects genetic material
Made of repeating building block units - capsomers

Question 4

What are capsomers

Answer 4

subunit of the capsid arranged in a precise and highly repetitive pattern around the nucleic acid. Made of globular proteins

Question 5

What are the three types of symmetry of the capsid

Answer 5

Helical
Icosahedral
Complex (Icosahedral head, helical tail)

Question 6

Outline the composition of viral genome

Answer 6

Nucleic acid - DNA or RNA
Linear, circular, or segmented
Single stranded or double stranded (for both DNA and RNA)

Question 7

How does genetic variation/new strands of virus arrise

Answer 7

Some virus strands can exchange/swap segments of genetic material, thus leading to new strands

Question 8

What do viruses infect

Answer 8

All cell types - eukaryotic and prokaryotic
All forms of life - animals, plants, bacteria, fungi, algae

Question 9

What is a host organism

Answer 9

An organism which a virus infects

Question 10

What is a host cell

Answer 10

A cell a virus multiples in

Question 11

What are bacteriophages

Answer 11

Viruses that infect and replicate in bacteria

Question 12

Outline the Lytic cycle

Answer 12

Bacteriophage infection
Attach
Penetrate
Uncoat (expose genetic material into host cell)
Genome replication & gene expression (synthesising proteins)
Assembly (assembly of replicated viral proteins)
Release

Question 13

Outline the 6 steps of virus infection

Answer 13

Attach (mediated by receptor)
Penetrate
Uncoat
Gene expression & Genome replication
Assembly
Release

Question 14

What type of virus is SARS-CoV-2

Answer 14

Enveloped
+ssRNA
Linear
Non segmented

Question 15

What does “+”… mean

Answer 15

Positive sense. Refers to fact genome can be directly translated into proteins (acts as mRNA)

Question 16

What does “-“… mean

Answer 16

Negative sense. Must be converted into complimentary strand before undergoing protein translation (e.g synthesising mRNA)

Question 17

Outline RNA polymerase in terms of Covid 19

Answer 17

Includes RNA polymerase to copy the genome.
Has limited proof reading so makes some errors/gene variants/mistake/ mutations, thus allowing tracking and leading to new strands

Question 18

What is the spike

Answer 18

Critical for attachment and cell entry
A Major target for neutralising immunity
Binds to specific cellular receptors
Vaccines target the spike

Question 19

Outline the SARS-CoV-2 replication cycle

Answer 19

Replicates occurs in the cytoplasm.
Spike binding toACE2 receptor
Cell entry/fusion
Genome replication, translation of replication module
Assembly
Exocytosis (exits through normal cellular processes via golgi)

Question 20

Outline the replication of RNA enveloped virus (HIV) retrovirus

Answer 20

HIV fuses with host cell membrane and digestion of capsid
Viral RNA reverse transcribed into RNA/DNA hybrid, then into DNA (reverse transcriptase).
Viral DNA incorporated into host genome (provirus)
Viral proteins and envelope glycoproteins transported to the plasma membrane
Progeny virus is assembled and exocytosed from the cell, with viral envelope glycoproteins (on host cell membrane)