Virusus and Subviral Particles

Question 1

what do viruses consist of?

Answer 1

a protein coat (capsid)

sometimes a lipid-containing envelope

Question 2

virus survival

Answer 2

they are obligate intracellular parasites, meaning that they cannot survive and replicate outside of a host cell.

Question 3

virions

Answer 3

individual virus particles

Question 4

bacteriophages

Answer 4

these are viruses that target bacteria.

• they contain a tail sheath, which injects the genetic material into a caterium.
• and tail fibers, which allow the bacteriophage to attach to the host cell

Question 5

viral genomes may be made of various nucleic acids

Answer 5

• they may be composed of DNA or RNA and may be single- or double-stranded.
• single-stranded RNA viruses may be positive sense (can be translated by the host cell) or negative sense (a complementary strand must be synthesized using RNA replicase, which can then be translated)

Question 6

Retroviruses

Answer 6

these contain a single-stranded RNA genome, to which a complementary DNA strnd is made using reverse transcriptase.
-the DNA strand can then be integrated into the genome

Question 7

how do viruses infect cells?

Answer 7

they infect cells by attaching to specific receptors, and then either fusing with the plasma membrane, being brought in by endocytosis, or injecting their genome into the cell

Question 8

how do viruses reproduce?

Answer 8

by replicating and translating genetic material using the host cell’s ribosomes, tRNA, amino acids, and enzymes

Question 9

Extrusion

Answer 9

when viral progeny are released through cell death

Question 10

bacteriophages have two specific life cycles, what are they?

Answer 10

• the lytic cycle: the bacteriophage produces massive numbers of new virions until the cell lyses. bacteria in the lytic phase are termed virulent
• lysogenic cycle: the virus integrfates into the host genome as a provirus or prophage, which can then reporduce along with the cell. The provirus then leaves the genome in response to a stimulus at some later time and enters the lytic cycle

Question 11

prions

Answer 11

these are infectious proteins that trigger misfolding of other proteins, usually converting an alpha-helical structure to a beta-pleated sheet.
-this decreases the solubility and degradability of the misfolded protein

Question 12

viroids

Answer 12

these are plant pathogens that are small circles of complementary RNA that can turn off genes, resulting in metabolic and structural derangements of the cell and- potentially- cell death