Ch38: Viruses

Question 1

Describe the structure of viruses

Answer 1

-Tiny, non-cellular
-Outer protein coat called capsid
-Contains DNA or RNA
-Few hundred genes
-No cytoplasmic organelles

Question 2

Living VS. Non-living features of Viruses

Answer 2

LIVING:
-Contain DNA or RNA
-Protein coat
-Can replicate

NON-LIVING:
-Non-cellular
-Cannot reproduce by themselves
-No cell organelles
-Only one type of nucleic acid

Question 3

What are obligate parasites

Answer 3

Require structures of a host cell to replicate themselves

Question 4

What is a bacteriophage?

Answer 4

Virus that infects bacteria

Question 5

Explain how viruses replicate

Answer 5

1. Attachment: attaches to host cell
2. Entry: forms hole in host cell and injects viral nucleic acid into cell
3. Synthesis: viral nucleic acid uses host organelles to make new viral nucleic acid and proteins
4. Assembly: new viruses are made using the viral mlecules that have been produced
5. Release: the host cell bursts (lysis) o release 100-100,000 new viruses

Question 6

What is a retrovirus?

Answer 6

A virus containing RNA instead of DNA
They contain enzymes that convert RNA to DNA in the host cell
E.g. HIV (Human Immunodeficiency Virus), virus that attacks cells that help the body fight infection

Question 7

AIDS:
1. What is it? Cause?
2. How is it transmitted
3. Effects
4. Control and Prevention

Answer 7

1. Disorder in which the person cannot make antibodies. Caused by infection with HIV
2. Sharing of body fluids like blood and semen
3. May enter WBC and either remain dormant or disable WBC (affecting production of antibodies, leading person to become vulnerable to infection)

. No cur, prevent by controlling sread

Question 8

Disadvantages of viruses

Answer 8

-Human diseases (flu, measles, ebola)
-Plant diseases (tobacco mosaic disease)
-Animal diseases (rabies, cowpox)

Question 9

Advantages to viruses

Answer 9

-Genetic engineering: viruses are used to transfer genes from one organism to another

-Control of infections: bacteriophages can be used to control bacterial infections, especially when bacteria becomes antibiotic-resistant

Question 10

Explain immunity in terms of viruses

Answer 10

-Controlled by the body’s general defence system and specific defence system

-Immunity to viruses can be induced by vaccination or injecting antibodies

-Antibiotics do not kill viruses

Question 11

What are interferons?

Answer 11

Chemicals produced by virus-infected cells to protect healthy cells
Can be made artificially to treat viral infections

Question 12

What are antiviral drugs?

Answer 12

Can be used to treat viral infections, but it is difficult iterfere with the virus without affecting the host cells