virus structure & replication

Question 1

describe the structure of a bacteriophage

Answer 1

a head which contains DNA, a collar sheath, base plate and tail fibres

Question 2

describe the structure of a retrovirus

Answer 2

contains reverse transcriptase enzyme, surrounded by proteins which help the virus enter host cells, RNA in the centre which contains genetic info and this is surrounded by a protein coat/capsid

Question 3

describe the first 3 stages in the lysogenic cycle

Answer 3

1. virus attaches onto host receptor molecules using attachment proteins. RNA is injected into the cell. Capsid is injected and RNA is released.
2. reverse transcriptase is used to make complementary strands of DNA from viral RNA.
3. the bacterial cell replicates and replicates the viral DNA. This is done through binary fission

Question 4

describe the final 2 stages in the lysogenic cycle

Answer 4

4. the daughter cells continue to function and replicate just as normal
5. a trigger or stress causes the cell to revert to the lytic cycle as viral DNA separates from the hosts DNA

Question 5

what causes a virus to switch between the lysogenic cycle to the lytic cycle?

Answer 5

a trigger or stress like not eating enough, a lot of stress or trauma

Question 6

describe the first 3 stages in the lytic cycle

Answer 6

1. the virus attaches onto hosts receptor molecules using attach meant proteins
2. the RNA is injected into the cell. The capsid is injected and RNA released.
3. reverse transcriptase is used to make complementary strands of DNA from viral RNA

Question 7

describe the final 3 stages in the lytic cycle

Answer 7

4. host cell enzymes are used to make viral proteins from viral DNA
5. viral proteins are assembled into new viruses
6. virus cells bud from cells and infect other cells . They leave when pulled out with some cell membrane

Question 8

can you kill a virus?

Answer 8

no, they aren’t living

Question 9

what do bacteriophages do?

Answer 9

infect bacteria but can’t bind with human cells

Question 10

describe viral replication

Answer 10

1. the virus attaches to the complementary receptors on the cell surface membrane of the host cell
2. the virus injects its genetic info into the host cell.
3. RNA is converted into DNA by reverse transcriptase
4. the cell replicates by mitosis and the viral DNA assembles and leaves the cell

Question 11

why are viruses described as acellular and non living?

Answer 11

they don’t contain a nucleus and don’t respire independently

Question 12

why aren’t antibiotics effective against viruses?

Answer 12

because viruses don’t have a cell wall