8. Viruses

Question 1

____: Submicroscopic, obligate intracellular parasite produced by assembly of pre-formed components which does not grow or divide and lacks the genetic information for energy production or protein synthesis.

Answer 1

Virus

Question 2

Virus structure:

Answer 2

1. Nucleuic Acid
2. Surrounded by a protein coat (Capsid)
3. May contain matrix protein outside nucleocapsid
4. May contain an envelope around the nucleocapsid
5. May contain peplomers (spikes)
6. Head Tail Bacteriophages

Question 3

The protein coat of a virus does what

Answer 3

Protects the viral genome from the outside environment

Question 4

The protein coat is constructed from many ____ proteins

Answer 4

subunit

Question 5

Helical (or filamentous) viruses

a. Capsid shape is a ____ with a hollow center.
b. Helical viruses can be very rigid, rod-like or if the rods are longer they can be somewhat flexible.
c. Two types of helical viruses
1) with nucleic acid in the hollow center
2) with nucleic acid wound in the helix

Answer 5

cylinder

flexible

Question 6

Icosahedral Viruses

a. Capsid shape is roughly a ____ made up of ____ equilateral triangles. Like geodesic dome buildings
b. An icosahedron has twenty triangular sides, but proteins are not triangles (most are globular). So, the virus actually has to use more than one protein subunit to make each triangle. Each protein subunit is called a ____. The smallest number of capsomeres in an icosahedral virus is 60 (3 per triangle).

Answer 6

sphere; twenty

capsomere

Question 7

The smallest number of capsomeres in an icosahedral virus is ____ (3 per triangle).

Answer 7

60

Question 8

Most ____ viruses are enveloped. Only a few ____ viruses are enveloped. There are also some enveloped viruses of prokaryotes

Answer 8

animal; plant

Question 9

Peplomers (spikes) are composed of ____

Answer 9

glycoproteins

Question 10

____ are involved in binding of the virus to its host receptor

Answer 10

Peplomers (spikes)

Question 11

____ are viruses that infect bacteria.

Answer 11

Bacteriophages

Question 12

Many bacteriophages have an ____ head attached to a rod shaped tail

Answer 12

icosahedral

Question 13

Bacteriophage

The tail contains a tail core is a hollow tube made of protein. The tail core is surrounded by proteins called the _____.

Answer 13

tail sheath

Question 14

What is this

Answer 14

Bacteriophage

Question 15

Life cycle of a virus

Answer 15

1. Recognition and attachment
2. Entry and Uncoating
3. Replication
4. Assembly and Packaging
5. Release

Question 16

in ____, the viral attachment protein is usually on the tail fibers. In ____ with peplomers, it is usually on the peplomers. In ____, it is on the capsid or envelope.

Answer 16

bacteriophage; viruses; viruses without spikes

Question 17

____ can only attach to and infect certain cells (the ones with the right receptors).

Answer 17

Viruses