VIRUSES CH 7 Flashcards
Identify better terms for viruses rather than alive or dead
Active / Inactive
T/F: Viruses are alive
False
Why cant viruses survive outside of a host cell?
They lack cell machinery
Identify the structures common to all viruses
- Capsid (protein coat)
- Nucleic Acid (DNA OR RNA)
- Spikes (Allow attachment to cell surface)
Identify the structures present in some viruses
- Accessory Proteins (specialized effects within the cell; “nice to have”)
- Envelope (extra outer layer made from OUR cell membrane acquired when they enter the cell to hide from our immune system) (or nuclear membrane as they leave the nucleus)
Identify the following structures; select which are present in all Viruses, AND describe their function
A - Accessory Proteins (specialized effects within the cell; “nice to have”)
B - Envelope (extra outer layer made from OUR cell membrane acquired when they enter the cell to hide from our immune system)
C - Spikes (Allow attachment to cell surface + allows them into the host)*
D - Capsid (Protein Coat)*
E - Nucleic Acid (DNA OR RNA; this is used to make more viruses)*
*Present in all viruses
Identify and describe the different viral shapes
Icosahedral - 3D Hexagon
Helical - Spiral Rods
Complex (bacteriophage) - Head, Tail, + Legs
Identify the viral shape
A - Icosahedral
B - Helical
C - Complex (Bacteriophage) (Only Infect Bacteria)
Enveloped vs Naked Viruses
Enveloped - Contain the host’s phospholipid bilayer;
allows it to go unrecognized by the immune system
Naked - Lack an envelope
Where are spike proteins attached?
On the outermost membrane of the virus
Naked: On the Capsid
Enveloped: On the Envelope
How do viruses leave the cell?
Naked Viruses have spikes on the capsid + must fill the host cell with viral particles to get out; When the cell is entirely filled the host cell breaks apart through lysis
Enveloped Viruses have spikes on the cell membrane + are wrapped as they leave the host cell; this is called budding
T/F: Viruses can be seen with a light microscope
False; they require electron microscopes
Viral Capsids are composed of what biochemical group? What are these individual subunits called
Protein; Capsomeres
What are the three unique forms of viral nucleic acid?
DNA
RNA
Reverse Transcriptase - RNA >DNA
Describe the viral life cycle
APUSAR
Adsorption - Spikes to stick to receptors on host cell
Penetration - Entry into the cell
Uncoating - Break capsid open + release nucleic acid
Synthesis - Form more viral capsids + nucleic acids
Assembly - Use capsids and nucleic acid to form more infectious particles +
Release - Leave to infect more cells
DNA vs RNA Virus
DNA Virus must go to the nucleus to trigger protein formation (DNA > mRNA > Protein)
RNA Virus stays in the cytoplasm (can make proteins within the cytoplasm)
What are the two things we want to know about a virus? Why?
DNA or RNA:
DNA virus goes to the nucleus to be turned into RNA and have an effect as proteins
RNA virus doesn’t need to go to the nucleus and can be translated in the cytoplasm
Naked or Envoloped:
Naked virus has spikes on the capsid and causes lysis to get out of the cell (must fully fill the cell with viral particles)
Enveloped virus sends spikes to the cell membrane and are wrapped around the virus on the envelope as they leave the cell
Define Provirus and Latent Phase
Inserts viral DNA into the host DNA; Can go into a latent phase where the trait is inactive but can be reactivated
Oncogenic Virus
Cancer causing virus
~13% of human cancer is caused by viruses
In Vitro vs In Vivo
They are both processes by which we grow viruses
In Vitro - Cells on a plate
In Vivo - Lab animals and bird eggs
T/F: Viral infections are more common than bacterial infections
True
T/F: Viral mutation rates are low and viruses are easy to track in a population
False; they mutate all the time and are impossible to track in a population
Doctors + Scientists most often rely on _______ to treat or prevent viral infections
Vaccines
Why is it difficult to create antiviral treatments?
Viruses use much of human machinery and therefore makes it difficult to target specific features without harming our own cells
What are prions?
Misfolded Proteins
How are prions misfolded?
Alpha helices are mutated to form beta pleated sheets
What organ do prions primarily affect?
Mainly the brain but also other regions of the nervous system including the spinal cord
Virus is the latin word for ________
Poison
Why are viruses considered obligate intracellular parasites? What host cell machinery do they use?
They must be inside of a cell and use host ribosomes and enzymes to make more viral DNA/RNA, spikes, and capsomeres
What is the size range of viruses? How do we view them?
Nanometer range; require electron microscopes
Genome
The full complement of dna and rna carried by a cell
Is the flu an RNA or DNA virus?
RNA
Is AIDS/HIV an RNA or DNA Virus?
RNA
List characteristics of viruses that distinguish them from cellular life
They lack ribosomes, enzymes, and hormones. They do not reproduce, and do not perform metabolism or chemical reactions
What enzymes do viruses use to speed up their processes within the host cell? How do they work?
Polymerases - Synthesizes DNA and RNA
Replicases - Copy RNA
How does reverse transcriptase work? What virus is known to have this enzyme?
Turns RNA into DNA and imbeds viral DNA in OUR genome
HIV
How do we meausre the amount of virus in a sample?
Put cells in a plate and cover the entire plate in agar; we then measure plaques; or the absence of cells in an area
T/F: The term plaques is only used to describe the effects of bacteriophage on cell cultures
False
How do vaccines work?
They are inactive viruses that teach our immune system how to respond to it so that we can fight it quicker with less symptoms and damage
what disease do prions cause?
Spongiform Encephalopathies (spongy brain)
