Download Biology I Test: Viruses and Immunology

Biology I Review: Viruses and Immunology ANSWERS
Instructions: Answer the following questions and will be prepared for tomorrow’s test!
1. What is a virus made of?
segment of DNA or RNA wrapped in a protein coat
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List five reasons why we consider viruses to be non-living.
Non-cellular (i.e. not a cell)
They do not use energy (They do not carry on respiration or photosynthesis)
No organelles
They Reproduce within cells; but not directly with other viruses
They do not grow in size
Contain nucleic acids and proteins
Have limited enzyme activity
3. List three characteristics viruses share with living things?
Have Nucleic Acids
Reproduce within cells
Have proteins
4. Do viruses usually have many or few hosts?
MANY
5. Viruses called bacteriophages attack what living things?
Bacteria
6. How can a virus find a host cell?
Receptor Proteins
7. When a virus takes over the machinery of a cell, what does it cause the cell to do?
DNA gets destroyed, cell dies
8. Name stages A-E of the lytic cycle
1. Attachment- The virus attaches to a specific area (receptor site) on a specific cell
2. Entry- the viral nucleic acid is then injected into the host cell.
3. Replication- host DNA is destroyed. Viral nucleic acid is replicated. Viral
components are manufactured
4. Assembly- viral components are assembled into mature viruses.
5. Release- Host cell lyses (splits open). This releases as many as 300 new viruses.
9. List the events that occur in stages A-E of the lytic cycle
1. Attachment- The virus attaches to a specific area (receptor site) on a specific cell
2. Entry- the viral nucleic acid is then injected into the host cell.
3. Replication- host DNA is destroyed. Viral nucleic acid is replicated. Viral
components are manufactured
4. Assembly- viral components are assembled into mature viruses.
5. Release- Host cell lyses (splits open). This releases as many as 300 new viruses.
10. What does latent mean?
DORMANT - does not attack immediately
11. What is a provirus and when is it formed? Why is the immune system ineffective
against a provirus?
Provirus Formation- viral DNA attaches to the host cell’s DNA forming a new
combination of DNA known as a provirus.
Immune system cannot detect it because the viral DNA is combined with the host DNA
12. Compare and contrast the lytic and lysogenic cycle?
1. Attachment and entrance are the same as in the lytic cycle.
2. Provirus Formation- viral DNA attaches to the host cell’s DNA forming a new
combination of DNA known as a provirus. A provirus is latent. (I.e. it does not
attack immediately)
3. Cell Division- cell undergoes normal asexual reproduction with replication of
both the host and viral DNA.
4. Activation- the provirus leaves the host DNA and reverts back to the lytic cycle
13. Would a person feel ill more quickly if they had a lytic or lysogenic virus?
LYTIC - faster replication
14. How is the AIDS virus spread?
A) Sexual Contact (Semen & vaginal secretions)
B) I.V. Drug Use (Direct contact with blood)
C) Mother to Baby (Across placenta, Breast milk)
15. What type of cells does HIV attack?
Immune cells (lymphocytes)
16. What is the body’s first line of defense against pathogens (germs)?
Barriers - skin, mucus, hairs
17. Openings in the body must be protected. Explain how the eye, ears and mouth are
protected.
a) Mouth- contains digestive enzymes
b) Nose- contains hair and mucus
c) Ears- has hair and wax
Eyes - natural saline solution
18. The foreign protein patterns on a germ are called ________________.
Antigens
19. What cells could engulf a germ by phagocytosis?
Macrophages and neutrophils
20. When a macrophage engulfs a germ, what does it become?
Antigen presenting cell
21. What type of cell binds to an APC (antigen presenting cell)?
T-cell
22. What happens when a T-cell binds with an APC?
Release chemicals to activate b cells
23. What do B-cells do?
Activate and divide forming plasma and memory cells
24. What is the function of a plasma cell?
a) secrete antibodies that bind to the antigen and immobilize it
25. Where do plasma cells come from?
b-cells
26. How do antibodies attack germs?
Attach to the antigen
27. When do memory cell form and what is their function?
When b-cells activate
a) Memory Cells persist after the infection and provide immunity
28. How does a vaccine work?
4. Vaccines contain dead or weakened germs and cause an immune response which
produces immunity without disease
29. How do cytotoxic T-cell or T-killers attack germs?
attack germs directly, release perforin and perforin punches holes in the germ and
destroys it
30. What activates Cytotoxic T-cell?
5. T-Cells also activate cytotoxic T-cells (T-Killers)