Viruses Flashcards
Viruses are very much part of life on Earth and the human experience. Viruses infect ___, ____ and even ___.
Animals Plants Bacteria
True or False Viruses are very difficult to classify and are currently not included in any of the major kingdoms.
True
What disease do tobacco plants suffer from? And what does it do?
Mosaic disease which attacks their leaves causing them to die.
Who carried out investigations to try and find out what caused this very disease?
A Dutch Scientist
Give a summary of the experiment behind the tobacco leaves. (3)
-The extracted juice of a tobacco plant suffering from mosaic disease was passed through a very fine filter -The resultant liquid, filtrate was applied to the leaves of the healthy plant -The leaves developed mosaic disease
What conclusions came about as a result of the experiment?
The filter was too fine to let through all known bacteria. It was realized that the tobacco mosaic, therefore, could not have been caused by bacteria. This was the first indication that disease-causing particles of submicroscopic sizes probably existed. The scientist named this infectious disease a ‘virus’ which is a Latin word meaning ‘poison’.
Forty years later with further investigations and with the aid of an ____ microscope, viruses could be identified and their characteristics established.
Electron
Why was the tobacco mosaic virus able to pass through the very fine filter, before viruses had been discovered?
It is now known that viruses are extremely small. For this reason, the tobacco mosaic virus in 1900 was able to pass through the very fine filter whose pores were small enough to keep back bacteria but too large to filter out viruses.
What are the characteristics of viruses? (7)
-Viruses exist in two distinct states- a virus and virion -Viruses are extremely -Viruses are not really living organisms -Viruses are obligate intracellular parasites -Viruses can only produce inside a living cell -Viruses are always associated with disease - Viruses can remain in a dormant state within an organism
What is the size of a virus?
A typical virus has a width of about ten-thousandth of a millimeter.
What are the two states of a virus? (2)
A virus when active and virion (when dormant and not into contact with the host cell)
Why are viruses not really living organisms?
Because they do not exhibit the characteristics of living organisms, ie they do not respire, feed, excrete, grow or move on their own.
Where do viruses reproduce?
They can only reproduce inside a living cell where the viral nucleic acids replicate using materials of the host’s cell to make many new viruses.
Viruses have no ____ or ____ to bring about replication on their own.
Organelles Cytoplasm
What does the virus do to the host cells?
Leave them damaged
How do viruses replicate?
What is the structure of a virus?
