Viruses Flashcards
What are viruses
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
What are the 2 parts viruses consist of, and the occasional third.
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
What is a viral capsid and what is it made of
Protein surrounds protects genetic material
Made of repeating building block units - capsomers
What are capsomers
subunit of the capsid arranged in a precise and highly repetitive pattern around the nucleic acid. Made of globular proteins
What are the three types of symmetry of the capsid
Helical
Icosahedral
Complex (Icosahedral head, helical tail)
Outline the composition of viral genome
Nucleic acid - DNA or RNA
Linear, circular, or segmented
Single stranded or double stranded (for both DNA and RNA)
How does genetic variation/new strands of virus arrise
Some virus strands can exchange/swap segments of genetic material, thus leading to new strands
What do viruses infect
All cell types - eukaryotic and prokaryotic
All forms of life - animals, plants, bacteria, fungi, algae
What is a host organism
An organism which a virus infects
What is a host cell
A cell a virus multiples in
What are bacteriophages
Viruses that infect and replicate in bacteria
Outline the Lytic cycle
Bacteriophage infection
Attach
Penetrate
Uncoat (expose genetic material into host cell)
Genome replication & gene expression (synthesising proteins)
Assembly (assembly of replicated viral proteins)
Release
Outline the 6 steps of virus infection
Attach (mediated by receptor)
Penetrate
Uncoat
Gene expression & Genome replication
Assembly
Release
What type of virus is SARS-CoV-2
Enveloped
+ssRNA
Linear
Non segmented
What does “+”… mean
Positive sense. Refers to fact genome can be directly translated into proteins (acts as mRNA)
What does “-“… mean
Negative sense. Must be converted into complimentary strand before undergoing protein translation (e.g synthesising mRNA)
Outline RNA polymerase in terms of Covid 19
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
What is the spike
Critical for attachment and cell entry
A Major target for neutralising immunity
Binds to specific cellular receptors
Vaccines target the spike
Outline the SARS-CoV-2 replication cycle
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)
Outline the replication of RNA enveloped virus (HIV) retrovirus
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)
