2.2 Viruses Flashcards
Are viruses living organisms?
- No.
Why are viruses not regarded as living organisms?
- They lack a metabolism of their own.
What are 2 things that all viruses have?
- Core of nucleic acid.
- Surrounded by capsid - a protein coat.
What is an additional features that some viruses have such as HIV have?
- Additional envelope of membrane made of lipids + proteins.
How do antivirals work?
- Inhibiting viral replication by the host cells.
When antivirals have not been developed, how is spread of viruses prevented?
- Disease control.
What is an example of where disease control was used to reduce the spread of a virus?
- 2014 Ebola outbreak in West Africa.
What are the systems of classifying viruses?
- Structure.
- Nucleic acid type.
What is the λ (lambda) bacteriophage host?
- Bacterium.
What is the structure of λ (lambda) bacteriophage?
- Head.
- Tail tube.
- Tail fibres.
What is the size (nm) of λ (lambda) bacteriophage?
- Head dia 50-60.
- Tail length - 150.
What is the nature of nucleic acid core in λ (lambda) bacteriophage?
- Double-stranded DNA.
What is the copying of nucleic acid core in λ (lambda) bacteriophage?
- Double-stranded DNA transcribed to mRNA.
What is the host of Tobacco Mosaic Virus?
- Plants, esp of tobacco fam.
What is the structure of Tobacco Mosaic Virus?
- Capsid of polypeptide building blocks arranged in spiral around canal containing RNA.
What is the size (nm) of Tobacco Mosaic Virus?
- Diameter - 18.
- Length - 300.
What is the nature of the nucleic acid core in Tobacco Mosaic Virus?
- Single-stranded RNA.
How is the nucleic acid core copied in Tobacco Mosaic Virus?
- RNA copied directly to mRNA.
What is the host of Ebola virus?
- Human ( esp endothelial cells, liver cells, immune cells, etc.).
What is the structure of Ebola Virus?
- “Snake” of RNA w outer protein coat.
What is the size (nm) of Ebola Virus?
- Diameter - 80.
- Length - 130,000.
What is the nature of nucleic acid core in Ebola Virus?
- Single-stranded RNA.
How is the nucleic acid core copied in Ebola Virus?
- RNA copied directly to form mRNA.
What does HIV stand for?
- Human Immunodeficiency Virus.
What is the host of HIV?
- Humans (T helper lymphocytes).
What is the structure of HIV?
- Enzymes + single-stranded RNA at centre.
- 2 layers of protein coats.
- Outside is capsule + glycoproteins.
What is the size (nm)of HIV?
- Diameter - 120.
What is the nature of the nucleic acid core in HIV?
- Single-stranded RNA.
How is the nucleic acid core copied in HIV?
- RNA reverse transcribed into double-stranded DNA.
- DNA incorporated into host cell’s DNA.
- Later transcribed to form mRNA.
What is the lifecycle of a λ (lambda) bacteriophage?
- Lytic cycle.
What are the steps in the lytic cycle?
- Phage absorbed onto bacterium + injects it’s DNA.
- Phage DNA replicated + bacterial DNA broken down.
- Many new phage particles are made by bacterium.
- Cell bursts + phage viruses are released.
- Cycle repeats.
What is viral latency?
- Period in which under control of specific latency genes, pathogenic virus remains dormant.
- Virus or nucleic acid is present inside infected cell but does not control cell’s activities.
What are the 2 types of viral latency?
- Episomal latency.
- Proviral latency.
What is episomal latency?
- Viral nucleic acid remains inactive but free in cytoplasm of nucleus of infected cell.
What is proviral latency?
- Viral nucleic acid becomes incorporated into DNA of host cell.
- Can become reactivated at any point.
