Lesson 8 (Viruses)

Question 1

When are viruses alive?

Answer 1

Viruses are only alive when they multiply within a host, using the host’s machinery.

Question 2

Viruses are?

Answer 2

obligatory intracellular parasites

Question 3

Characteristics of a Virus

Answer 3

have either RNA or DNA (never both)

DNA can be single or double stranded, linear or circular

use the machinery of it’s host to multiply

contain a capsid, protein coat surrounding nucleic acid

lack enzymes to perform protein synthesis and ATP

Question 4

Host Range

Answer 4

spectrum of host cells that a virus can infect

Question 5

For infection to occur?

Answer 5

outer surface of the virus must chemically interact with specific receptor sites on the surface of the cell it’s trying to invade

Question 6

Animal Virus receptor site?

Answer 6

Plasma Membrane of host cell

Question 7

Bacteriophage receptor site?

Answer 7

part of host cell wall, part of fimbrae, flagella

Question 8

Virion

Answer 8

complete, fully developed, infectious particle which contains capsid

Question 9

Whats the viral size range?

Answer 9

20 - 100 nM

Question 10

Capsid

Answer 10

nucleic acid of virus is surrounded by protein coat

contain capsomeres, or protein subunits

capsomeres can be one or several proteins

Question 11

What is the arrangement of Capsomeres indicative of?

Answer 11

particular type of virus

Question 12

What is the function of the Capsid’s protein subunits (Capsomeres)?

Answer 12

protect nucleic acids from nuclease enzymes in biological fluids, promotes attachment to host

Question 13

Why can you get the same virus more than once?

Answer 13

When virus attaches to host, body produces antibodies against virus. Next time virus attacks, antibodies protect.

Question 14

How come there are many different strains of some viruses?

Answer 14

because that virus has many different surface proteins

Question 15

Morphology structure is revealed by?

Answer 15

Morphology structure is revealed by electron microscope.

Question 16

Morphology types are based on?

Answer 16

Morphology types are based on Capsid structure.

Question 17

What are some of the different morphology’s of viruses?

Answer 17

Helical Viruses
Enveloped Viruses
Polyhedral Virus
Complex Viruses

Question 18

Taxonomy of viruses groups viruses into families based on?

Answer 18

Nucleic acid type
Strategy for replication
Morphology

Question 19

Viral Species

Answer 19

a group of viruses sharing the same genetic information and ecological niche (host range)

Question 20

How are bacteriophages grown in a lab?

Answer 20

In suspension of bacteria either solid or liquid form

Question 21

What is the method used for detecting bacteriophages?

Answer 21

Plaque Method of detection (clearing of bacteria)

Question 22

Identify the three methods for growing animal viruses in a lab.

Answer 22

Living animals, embryoniated eggs, cell cultures

Question 23

Host cell supplies?

Answer 23

ribosomes and tRNA for protein synthesis
amino acids
atp

Question 24

What happens when host invades a virus?

Answer 24

changes cell, then kills cell

Question 25

The way viruses ___________ varies, but the ways viruses ________ is similar in all viruses.

Answer 25

The way viruses enter and exit varies, but the way viruses multiply is similar in all viruses.

Question 26

Lytic Cycle

Answer 26

replication of viral particles, ends with lysis and death of host cell

Question 27

Lysogenic Cycle

Answer 27

Incorporate part of viral DNA into host cell, change host cell’s DNA, viral DNA direct replication of viral particles, enters/proceeds with lytic cycle.

Question 28

What are the 5 stages of Bacteriophage multiplication?

Answer 28

Attachment, Penetration, Biosynthesis, Maturation, Release

Question 29

What are some of the differences between animal viruses and bacteriophages?

Answer 29

• mechanism of entering host
• synthesis and assemble of new viral components, are different because of difference in prokaryotic and eukaryotic cells
• mechanism of maturation, release and effect on host cell