Viruses

Question 1

Virus Facts

Answer 1

acellular (not a true living cell- no nucleus or organisms)
small- only seen with an electron microscope
obligate intracellular parasite (have to be in host cell to reproduce)
only 2 components (viral genome and protein coat)

Question 2

Bacteriophage

Answer 2

a virus that infects and replicates inside a bacterial cell

-most of what we know has dealt with E. coli and viruses

Question 3

Viral genome

Answer 3

either DNA or RNA, never both

Question 4

Protein coat

Answer 4

capsid

Question 5

Capsomere

Answer 5

subunits that make up the capsid

Question 6

Nucleocapsid

Answer 6

genome and capsid of a virus

Question 7

The capsid functions:

Answer 7

1) gives shape or symmetry
2) protective covering for the genome
3) capsid spike proteins (not found on all viruses) - they assist in attachment and penetration

Question 8

naked virus

Answer 8

viruses consisting of only the nucleocapsid

Question 9

enveloped viruses

Answer 9

have a flexible membrane called an envelope- envelope is composed of lipids and proteins

Question 10

virion

Answer 10

completely assembled virus outside its host cel

Question 11

Viral shapes

Answer 11

helical- tightly wound, resembles a spring
icosahedron- 20 triangular faces and 12 corners
complex- combination

Question 12

host range

Answer 12

variety of species that a virus can infect- most have a narrow host range

Question 13

tissue tropism

Answer 13

refers to specific tissues within a host that a virus infects
example- HIV - blood tissue
Rabies- nervous tissue

Question 14

3 ways to classify viruses

Answer 14

1) group based on tissue they affect
pneumotropic - respiratory
dermotropic- skin and subcutaneous layer
viscerotropic- blood and visceral organs
neurotropic- CNS
2) what family they belong to
3) are they DNA or RNA viruses

Question 15

Lytic cycle steps

Answer 15

1) attachment- phage’s tail fibers match with a receptor site on the bacterium’s cell wall- not a random attachment- complementary receptor sites on the bacteria’s cell wall
2) penetration- phage tail releases lysozyme to dissolve portion of the cell wall- lysozyme is an enzyme that dissolves a portion of the cell wall- tail sheath contracts and the tail core injects the DNA into the host cell, virus capsid stays outside only the genome goes in the host
3) biosynthesis- production of new phage and genome and capsid parts
4) maturation- assembly of viral parts into complete virus particles
5) release- exit of virions from the bacterium- lysis stage when the cell is ruptured- enzyme lysozyme is released again and it degrades the cell wall- death to host cell

Question 16

Lysogenic

Answer 16

does not always kill the host cell- phage DNA integrates into the bacterial chromosome as a prophage- bacteriophages that participate in this type of reproduction are known as temperate phages- bacteria survives the infection and continues to grow and divide normally- a prophage is the viral nucleic acid of the bacterial virus that is inserted into the bacterial DNA and is passed from one generation to the next

Question 17

prophage

Answer 17

virus DNA + bacterial DNA

Question 18

Antibiotics and viruses

Answer 18

antibiotics will not work because viruses lack the elements with which antibiotics interfere

Question 19

Antiviral drugs work to:

Answer 19

1) affect viral penetration/uncoating
2) alter genome replication
3) alter the maturation and release phase of replication

Question 20

Interferons

Answer 20

group of naturally produced proteins that trigger a non-specific reaction to protect us against a virus- IFN and INF beta don’t attack the virus itself- bind to specific receptor sites on the surface of adjacent healthy cells and triggers the healthy cells to produce antiviral proteins that attempt to inhibit viral replication

Question 21

Cancer

Answer 21

uncontrolled growth and spread of cells

Question 22

Tumor

Answer 22

clone of abnormal cells

Question 23

Metastasis

Answer 23

tumor that has spread

Question 24

Carcinogens

Answer 24

cancer causing substance