viruses Flashcards
what is a virus?
an infectious agent
what are the living features of a virus?
can mutate and reproduce rapidly (only in a living host cell)
what are the non-living features of a virus?
no cytoplasm or cellular organelles
does not carry out metabolism– replicates using host cell’s metabolic machinery
viruses don’t grow and divide, instead ________
new viral components are synthesized and assembled within the infected host cell
genome
the virus’s genetic material
the genome can be ________ or _______, but never both
single stranded / double stranded
the genome codes for the ___________
synthesis of viral components and viral enzymes for replication
capsid
protein shell surrounding the genome
what is the function of the capsid?
protect and introduce the genome into host cells
what is a virus that is just a genome surrounded by a capsid called?
nucelocaspid or naked virus
___________ project out from the capsid and binds the virus to a susceptible host
attachment proteins
envelope
surrounding a polyhedral or helical nucleocaspid
where does the envelope come from?
the host cell’s nuclear membrane, vacuolar membrane, or outer cytoplasmic membrane
the envelope is usually of host cell origin, but the virus incorporates _________, which appear as ________ spikes
proteins of its own / gycoprotein
what is the function of the glycoprotein spikes?
attaching the virus to receptors on susceptible host cells
how does a virus cause disease?
uses another living host organism to reproduce
- there are so many viruses in the cell that it bursts and the viruses are free to move on to other cells in the host
- process repeats
what are virus vaccines made of?
inactivated or attenuated viruses
inactivated virus
does not replicate in a host cell
attenuated viruses
genetically altered; cannot cause disease
why are viral infections difficult to cure?
once inside the host, most substances that destroy the virus are also harmful to the host organism
what were the first viral vaccinations for?
measles, mumps, rubella
what are current viral vaccinations?
hepatitis A and B, chickenpox, smallpox, rabies
antiviral drugs
interfere with the synthesis of viral nucleic acid or with the formation of viral caspids during replication
antibiotics
no use for fighting viruses
why are antibiotics not used in curing viral infections?
they attack the metabolism of a bacterial cell
-viruses do not have metabolism
2 ways the body fights viruses
white blood cells
interferon
white blood cells
engulf viruses in the blood and “digest” them
interferon
a protein produced by cells when exposed to a virus
- binds the cell membranes of neighbouring cells
- interferes with the ability of a virus to enter the cell
public health strategy
a coordinated effort to track, research, and reduce the incidence of specific health problems in a population
vaccination
the process of giving a vaccine by mouth or injection to provide active immunity against a disease
what are infectious diseased caused by?
pathogens (viruses, bacteria, fungi) entering the body
what organ is the first line of defense that stops pathogens?
skin
what does the immune system do to fight off pathogens?
send a flow of white blood cells (phagocytes) and dissolved substances to the site of the infection, causing inflammation
what does bone marrow produce to help fight off pathogens?
white blood cells and disease-fighting molecules
antigen
any material that the body considers foreign and triggers phagocytes
antibodies
specialized proteins found in phagocytes
