1.9 Viruses

Question 1

In 1852, a Russian scientist discovered that certain diseases could be transmitted by agents that

Answer 1

Unlike bacteria can pass through very fine filters

Question 2

Viruses are on the boundary between

Answer 2

What we think of as living and nonliving

Question 3

Define virus

Answer 3

A very small (20– 300 nm) infectious particle, which can replicate only inside living cells.

Question 4

Unlike prokaryotes and eukaryote viruses do not have a cell structure. Explain what this means.

Answer 4

It means they are not surrounded by a partially permeable membrane containing cytoplasm with ribosomes.

Question 5

What do viruses consist?

Answer 5

• self replicating, molecule of DNA or RNA (the genome complete genetic instructions)
• protective coat of protein molecules called a capsid
•(some viruses only) a membrane like outer layer, called the envelope that is made of phospholipids. Proteins may project from the envelope.

Question 6

Viruses typically have a very ________ shape

Answer 6

Symmetrical

Question 7

What is a capsomere

Answer 7

The separate protein molecules that make up the protein coat.

Question 8

All viruses are parasitic. What does this mean?

Answer 8

They can only reproduce by infecting and taking over living cells. The virus DNA or RNA take over the protein synthesizing machinery of the host cell which then helps to make new virus particles.