Exam 2: Viruses

Front 1

how were viruses first discovered?

Back 1

through the filtration experiment
cell filtrate infected the plant
smaller than a bacterium because the cell debris collected by membrane was too big for bacteria

Front 2

what is the best way to view a virus?

Back 2

electron microscope at 7000x

Front 3

what are 3 general properties of viruses?

Back 3

1) extremely small particles
2) all are obligate intracellular parasites
3) very simple structure

Front 4

what is a genome and how does the genome of a virus differ from that of a prokaryote or a eukaryote?

Back 4

all the genetic information of an organism
prokaryotes and eukaryotes have DNA and RNA
viruses have DNA or RNA

Front 5

what are 2 unique genomic structures found only in viruses?

Back 5

1) single stranded DNA
2) double stranded RNA

Front 6

what do viruses need so few genes compared to prokaryotes and eukaryotes

Back 6

they sponge off their host using many of the cell's normal cellular processes and machinery

Front 7

what is a viral capsid

Back 7

protein shell

Front 8

what is the role of the viral capsid and what is it composed of?

Back 8

surrounds and protects the genetic material of the virus
made of up individual proteins called capsomeres

Front 9

how can capsids differ between viruses

Back 9

can be made up of a single type of protein capsomere, several different types of protein capsomeres, different shapes, number of capsomeres that make up the capsid

Front 10

where are viral spikes located and what is their function?

Back 10

project from the capsid promotes viral attachment to host cells

Front 11

what is a viral envelope?

Back 11

envelope composed of lipid bilayer with carbs and proteins, including viral spikes

Front 12

where does the viral envelope originate from and what is its function?

Back 12

from the membrane of the eukaryotic cell the virus infected and destroyed
further protects the genetic material

Front 13

what is a virus called if it does not have an envelope?

Back 13

naked

Front 14

what are the 4 types of virus morphology?

Back 14

1) helical viruses
2) icosahedron
3) enveloped
4) complex

Front 15

how are viruses classified today?

Back 15

based on nucleic acid sequences and viral structures

Front 16

what reasons might there be for the yearly increase in the number of species identified?

Back 16

evolution, closer to different species

Front 17

what are the steps involved in the infectious cycle of an animal virus?

Back 17

1) attchment
2) entry
3) uncoating
4) biosynthesis
5) assembly
6) release

Front 18

what is a susceptible host cell and what is a host cell receptor?

Back 18

susceptible host cell - any cell that can be infected by a virus
host cell receptor - protein or glycoprotein on the surface of a cell; required for normal cellular functions

Front 19

define the terms broad host range, restricted host range, and tissue tropism

Back 19

broad host range - virus can infect many different species because of a common receptor shared by many different species
restricted host range - virus can only infect 1 specific species because receptor is unique to 1 species
tissue tropism - virus that infects 1 specific cell type because receptor is unique to 1 type of cell

Front 20

describe 2 ways that a virus can enter a host cell

Back 20

1) receptor-mediated endocytosis
2) membrane fusion

Front 21

explain what virus needs to do in terms of uncoating after entering by each mechanism.

Back 21

uncoating - release the virus's genomic material in the cytoplasm of the host cell
1) vesicle broken down
2) if virus is enveloped, envelope must be broken down
3) viral capsid must be broken down

Front 22

what are 3 critical things a virus needs to do to make new virus particles?

Back 22

1) replicate and make new copies of its genetic material
2) make new capsomeres for capsids
3) make new viral spike proteins

Front 23

describe the assembly process for a naked virus and an enveloped virus

Back 23

putting the capsid together from the capsomer subunits and viral spikes
getting the genetic material into the capsid

Front 24

describe the assembly process for an enveloped virus

Back 24

putting the capsid together from the capsomere subunits
getting the genetic material into the capsid
putting the viral spike proteins on the surface of the host cell plasma membrane

Front 25

explain the 2 ways a virus can be released from an infected cell. In general, what types of viruses escape by each method?

Back 25

1) cell lysis - naked and complex
2) budding - enveloped

Front 26

describe the difference between the infectious cycle of an animal virus and a plant virus and explain why this difference is necessary.

Back 26

plant viruses enter a plant cell at an open wound or via a plant parasite or insect that carries the virus

Front 27

what are viruses that infect bacteria called?

Back 27

bacteriophage

Front 28

describe the bacteriophage lytic cycle and what occurs at each step.

Back 28

1) attachment
2) penetration
3) biosynthesis
4) assembly
5) release