Viruses

Question 1

Viruses are

Answer 1

are non-cellular infectious particles that straddle the boundary between ‘living’ and ‘non-living’

but not living as cant reproduce on its own

Question 2

They are relatively simple in structure; much smaller than

Answer 2

prokaryotic cells (with diameters between 20 and 300 nm)

Question 3

Structurally they have:

Answer 3

A nucleic acid core (their genomes are either DNA or RNA, and can be single or double-stranded)

A protein coat called a ‘capsid’

Question 4

Some viruses have an outer layer called an

Answer 4

Lipid envelope formed usually from the membrane-phospholipids of a cell they were made in

helps protect the virus from the host’s immune system.

Question 5

All viruses are parasitic in that they can only

Answer 5

reproduce by infecting living cells and using their protein-building machinery (ribosomes) to produce new viral particles

Question 6

Attachment proteins are present on the surface of the capsid. The virus uses the attachment proteins to

Answer 6

to bind to host cells in order to infect them

Question 7

The enzyme reverse transcriptase is a enzyme that is found in only some viruses and bacteria and

Answer 7

catalyses the formation of a double strand of DNA from a single strand on RNA.