Viruses Flashcards
1
Q
How were viruses discovered
A
Tobacco plants can suffer from mosaic disease which attacks their leaves causing them to die. In 1900 a scientist carried out an investigation and since the disease was caused by something smaller than a bacteria, the scientist called it a virus
2
Q
Characteristics of viruses
A
- Viruses are extremely small - they can only be seen with an electron microscope
- Have two distinct states: a virus (when active, and a virion (when dormant and not in contact with a host cell)
- Not living organisms
- Can only survive inside the cells of living organisms
- Can only reproduce inside a living cell
- Viruses can remain in a dormant state
- Various shapes
3
Q
Different shapes of viruses
A
- Polyhedral: has twenty triangular faces
- Helical: resembles a coiled spring
- Complex: has a head, sheath and tail fibres
4
Q
Structure of viruses
A
- viruses are acellular, it is not a cell (has no nucleus, cytoplasm or organelles)
- has a core of DNA or RNA, can’t be both
- nucleic acid is surrounded by a protein coat or capsid
- some can be covered by an envelope of a lipid bilayer