Introduction to virology Flashcards
• What is a virus?
A virus is an infectious, obligate intracellular parasite comprising genetic material (DNA or RNA) surrounded by a protein coat and/or a membrane
Why is a virus described as a parasite?
A virus is a described as a parasite as it relies on host cells to replicate and also because it enters a cell and utilizes it for its benefit
What makes a virus infectious?
A virus is infectious because it travels from cell to another
Why is a virus obligate intracellular?
A virus is obligate intracellular because it requires a cell in order to replicate – as it doesn’t have enough machinery to operate on its own
The difference and similarity between viruses
Viruses may differ in size and shape but they all contain a genome in the middle that is protected by a protein
What do the proteins that stick out of the surface of the virus enable?
The proteins that stick out of the surface of the virus enables the virus to interact with the host cell it wants to infect
What does the envelop embed?
The envelop embeds proteins
What is a virus?
“A virus is a piece of bad news wrapped in protein”
Peter Medawar
A virus is an organism with 2 phases:
- Virion phase
The virus is free floating - Infected cell phase
The virus has engaged with the host cell and has started its replication cycle before its liberation as a free virion
What is a virion?
A virion is a complete, mature, infectious viral particle
• Briefly describe the process of infection
When a virion infects a host cell, it is disassembled
The infected host cell then makes building blocks for new virions
The virus exits the cell and enters a new cell to start another round of replication
Viruses infect all living things
What is used when viewing ribosomes, proteins and small molecules?
Magnetic resonance and X – ray crystallography is used when viewing ribosomes, proteins and small molecules
What does NMR stand for?
NMR stands for nanometre range
How many viruses can fit on the head of a pin?
2mm = 2000 microns
About 500 million rhinoviruses can fit on the head of a pin
What does Rhinovirus cause?
Rhinovirus causes the common cold
Properties of viruses: Viruses are smaller than bacteria
- Almost all viruses are sub microscopic i.e., they can only be visualised by electron microscopy
- Diameter: 10 – 1000 nm (most 20 – 300 nm)
- Larger viruses can be viewed using a light microscope
What type of genome do viruses contain?
• Viruses contain only one type of nucleic acid, either DNA or RNA, but never both
What is the nucleic acid surrounded by?
• The nucleic acid is surrounded by a protein coat
What do some viruses have?
• Some viruses have an additional lipoprotein envelope
How do viruses replicate?
• Viruses replicate by “tricking” cells into making multiple copies of viral nucleic acid and protein, which then self – assemble to form new virus particles
Which organelles are missing in viruses?
• Viruses don’t have organelles, such as mitochondria and ribosomes
Viruses can’t replicate…
outside living cells
Viruses don’t undergo…
binary fission like bacterial pathogens - Viruses don’t grow
Viruses don’t have mitochondria. What does the mean?
Viruses can’t generate their own energy/metabolism
Viruses don’t move on their own, i.e.
Movement is passive as they don’t have a flagellum
What are differences between viruses and unicellular microorganism?
Size
unicellular microorganisms are microscopic i.e., a light microscope is used; viruses are sub - microscopic i.e., a electron microscope is used.
Grow in non - living media
Unicellular microorganisms grow in non - living media. Example: Agar; Viruses don’t grow in non - living media
Binary fission [subdivide and replicate themselves]
Unicellular microorganisms undergo binary fission; viruses don’t
Contain both DNA and RNA
Microorganisms contain a DNA genome and utilized RNA to fulfil transcription and translation; Viruses contain only one genome
Infectious nucleic acid
Microorganisms don’t contain an infectious; viruses do
Ribosomes
Microorganisms contain ribosomes; viruses don’t
Generate energy
Microorganisms generate energy; viruses don’t
What are consequences of having a virus?
- Severe infections +/- hospitalisation
- Chronic infections +/- sequelae such as cancer
- Requirement for long term therapy
- Death
When was the 1st written record of virus infection?
approximately 3700 BC (temple priest): clinical signs of Paralytic poliomyelitis seen in hieroglyphics in Memphis
What did polio cause and in which years did it spread?
• Polio caused disease in Ancient Egypt and continued spreading well into the mid –1900s and the late 1900s
When did the influenza pandemic spread?
• There was an influenza pandemic that spread around the early 1900s – it travelled in waves and it killed millions of people [influenza pneumonia]
