Chapter 38: Viruses

Question 1

Describe the structure of a virus

Answer 1

non cellular
50x smaller than bacteria
no organelles
have a protien coat (capsid) that surrounds the nucleic acid

Question 2

What are the two types of nucleic acid?

Answer 2

RNA

DNA

Question 3

What makes a virus living?

Answer 3

possess genetic material
possess a protein coat
can replicate

Question 4

What makes a virus non-living?

Answer 4

non cellular
cannot reprouduce themselves
no organelles
only one type of nucleic acid

Question 5

Viruses are obligate parasite, what does this mean?

Answer 5

they need a living host to survive

Question 6

What are the 5 stages of replication?

Answer 6

attachment
entry
synthesis 
assembly
release

Question 7

Explain attachment.

Answer 7

virus attaches to host cell

proteins on virus line up with receptors on host cell

Question 8

Explain entry.

Answer 8

hole formed and viral nucleic acid enters

Question 9

Explain synthesis.

Answer 9

host DNA made inactive

viral nucleic acid uses organelles to produce new nucleic acid and proteins

Question 10

Explain assembly.

Answer 10

new viruses are made using new molecules

Question 11

Explain release.

Answer 11

host cell bursts (lysis)

Question 12

What is lysis?

Answer 12

when the host cell bursts due to a virus formed inside it

Question 13

Explain how variation in human cells occurs due to a virus.

Answer 13

some viruses dont destroy a hosts DNA but join it

Question 14

What are the advantages of a virus?

Answer 14

genetic engineering - viruses used to transfer genes from one organism to another
control of infections - bacteriophages used to control bacterial infections resistant to antibiotics

Question 15

What are the disadvanges of viruses?

Answer 15

disease
plants - tobacco/tomato/potato mosaic disease
human - colds, flues, aids
animal - foot and mouth, cowpox, rabies

Question 16

What does aids stand for?

Answer 16

Acquired immune deficiency syndrome

Question 17

What does hiv stand for?

Answer 17

Human immunodeficiency virus

Question 18

How is aids transmitted?

Answer 18

Enters via bodily fluids e.g. blood, semen Through shared needles, sexual intercourse

Question 19

What are the effects of aids?

Answer 19

Enters wbc

Can remain dormant or disable wbc (helper t-cells)

Question 20

What is the effect of aids disabling helper t-cells?

Answer 20

Prevents the person from producing antibodies

Unable to fight off infection

Question 21

How can aids be controlled?

Answer 21

No cure
Prevents by avoiding sexual intercourse or use a condom
Don’t share needles, toothbrushes, razors, donate blood,semen or body organs

Question 22

What is interferon?

Answer 22

A substance produced by virus infected cells to protect healthy cells

Question 23

How can immunity be controlled?

Answer 23

Defence System in the Body
Vaccinations
Antibody injections
Antiviral drugs
Acyclovir - treats herpes 
AZT - slows the development of aids