viruses

Question 1

why are viruses not considered truly alive?

Answer 1

 Do not maintain homeostasis
 Cannot reproduce on their own

Question 2

virus structure:

Answer 2

genetic material (DNA or RNA) inside a protein case

Question 3

basis of how virus functions

Answer 3

o Since they cannot reproduce on their own, they attack and hijack other cells. The genetic material they have is instructions to make more of that virus, but they need a host cell to do that.
 Inject mRNA into host cells
 problem since ribosomes translate most mRNA they find

Question 4

components of virus

Answer 4

capsid, viral envelope, nucleic acid, enzymes

Question 5

capsid

Answer 5

protein shell that makes up the surface of virus
* Shape may be simple or complex

Question 6

bacteriophages (phages)

Answer 6

virus that is large, complex, and attacks bacteria

Question 7

viral envelope

Answer 7

virus surrounded by membrane they took from a host cell

Question 8

purpose of viral envelope?

Answer 8

For viruses that attack animals: envelope is part of membrane of animal cell, so viruses can take a part of the membrane with it. Why? Let’s it hide more effectively from immune system.

Question 9

viruses sneak into other cells to use their?

Answer 9

ribosomes

Question 10

is a virus specific?

Answer 10

yes, can usually only attack one species or very similar species

The molecular basis for this specificity is that a particular surface molecule, known as the viral receptor, must be found on the host cell surface for the virus to attach.

Question 11

prophage is a virus that

Answer 11

integrates its DNA into host DNA
*virus is duplicated when host divides

Question 12

prophages can become active again if

Answer 12

environment changes

Question 13

restriction enzymes

Answer 13

defense that bacteria use to destroy viral DNA

Question 14

animal viruses have different nucleic acids :

Answer 14

 Double stranded DNA
 Single stranded DNA
 Double stranded RNA
 Single stranded RNA

Question 15

retroviruses have more complicated life cycle because

Answer 15

they use RNA as their genetic material, so they have to turn their RNA into DNA, which the host cell can then copy

Question 16

retroviruses use an enzyme called ____ to….

Answer 16

reverse transcriptase; turns RNA to DNA back to RNA

Question 17

retroviruses can integrate their DNA into animals DNA in nucleus, which means

Answer 17

when the cell multiples, it also multiplies the virus.

Question 18

provirus

Answer 18

viral DNA integrated into host DNA (stage of viral replication)

Question 19

HIV is an example of

Answer 19

retrovirus

Question 20

HIV patients always have to take medications because

Answer 20

the HIV is hiding in the cell’s DNA (no cure) and it can come back any time (RETROVIRUS)