Viruses Flashcards
what are some characteristics of viruses?
miniscule
acellular
have DNA or RNA
cause infection in humans, animals, plants, bacteria
no metabolic pathway
cause most diseases in industrialized world
neither grow nor respond to environment
obligate intracellular parasites (can’t reproduce independently)
no cytoplasmic membrane, organelles, cytoplasm
examples of virus families & what they can cause
Paramyxoviridae - mumps
Coronaviridae - covid-19
one virus particle
virion
nucleic acid surrounded by protein coat
nucleocapsid
how can viral genomes differ from one another?
DNA or RNA
linear or circular
one piece or segmented
the capsid is made of __________
capsomeres
what is the difference between naked & enveloped viruses?
enveloped have a phospholipid bilayer around their nucleocapid acquired from a host cell
naked do not
are naked or enveloped viruses tougher?
naked
do naked or enveloped viruses have more of an advantage inside the host?
enveloped
what are an enveloped virus’s advantages?
hides it from immune system
can fuse with cell membrane to infect it
what can damage an enveloped virus?
heat, freezing, pH change, chemical disinfectants, lipid solvents
what do some viruses have that help them attach to host cells?
glycoprotein spikes
3 virus shapes
icosahedral
helical
complex
5 steps of animal virus replication
attachment
penetration & uncoating
synthesis of viral proteins & replication of genome
assembly
release
viruses need __ receptors on a cell’s surface to attach
2
how do enveloped vs naked viruses attach?
enveloped - spikes attach to cell’s receptors
naked - capsid attaches to cell’s receptors
how do nakes vs enveloped viruses attach?
naked: capsid attaches to receptors on cell
enveloped: protein spikes attach to receptors on cell
how do enveloped viruses penetrate cell?
fusion with cell membrane
endocytosis
how do naked viruses penetrate cell?
direct penetration - genome directly through cell membrane
endocytosis
explain uncoating
viral nucleic acids and enzymes are released from protein coat
RNA remains in cytoplasm, DNA goes to nucleus
explain replication of DNA viruses
mostly occurs in nucleus
virus encodes its own enzymes - DNA polymerase
may embed themselves in host’s genome and become latent viruses/proviruses
explain replication of RNA viruses
occurs in cytoplasm
uses viral enzyme replicase (same as RNA polymerase)
many mutations occur (lack of proofreading)
explain reverse transcribing viruses
used by retroviruses
encodes enzyme reverse transcriptase
synthesizes DNA from a strand of RNA
also become proviruses/latent viruses
examples of reverse transcribing viruses
HIV
HTLV
examples of RNA viruses
influenza
SARS-CoV-2
examples of DNA viruses
herpes
human papilloma virus
explain assembly
virus particles assembled to form viruses
what are the 2 types of release?
budding - used by enveloped viruses - triggers apoptosis
lytic cycle - used by naked viruses - body’s immune defenses may lyse infected cell
what are the 2 types of viral infection?
acute - sudden onset, short duration
persistent - lasts years to life
what are 2 types of persistent infection, and examples?
chronic - continuous production of viral particles - Hepatitis B
latent - viral genome remains silent in cell until triggered to reactivate - herpes
pathogenesis of herpes
initially affects epithelial cells - slow-spreading skin lesions
then infectsneurons - travels up neurons into specific ganglia
viruses caus ___% of human cancers
20-25%
what are oncogenes?
genes that can transform a cell into a tumor cell
how can viruses cause cancer? (3 ways)
carry copies of oncogenes in their genomes
promote oncogenes in host
interfere with tumor repression
6 examples of cancer-causing viruses and their cancers
human papillomavirus (HPV) - cancer of cervix, vulva, vagina, penis, anus, oropharynx
hepatitis B - liver cancer
hepatitis C - liver cancer
Epstein-Barr - cancer of nasopharynx, Burkitt lymphoma
herpesvirus type 8 - Kaposi sarcoma
human t-lymphocyte virus (HTLV) - leukemia, lymphoma
2 ways we can grow viruses
human cell culture
embryonated chicken eggs
common cold infects the…
upper respiratory tract
common cold viruses
rhinoviruses
coronaviruses
adenoviruses
pathogenesis of common cold
respiratory epithelial cell destruction
common cold transmission & incubation
droplet, direct, indirect, airborne (maybe)
24-48hrs
what is the biggest health concern with common colds?
secondary infections
influenza infects…
upper & lower respiratory tract
type of influenzavirus
A, B, C in humans
influenza pathogenesis
destroys respiratory epithelium
transmission & incubation of influenza
droplet, direct, indirect, airborne (likely)
48hrs
antivirals for influenza work during _______ stages and include 2 drugs:
early stages
Tamiflu
Zofluza
2 types of protein spikes on influenzaviruses
hemagglutinin
neuraminidase
this type of influenza caused the Spanish Flu and Swine Flu outbreaks
H1N1
2 mechanisms by which influenzavirus mutates
antigenic drift - random mutations occuring in types A & B
antigenic shift - mixture of genes from two strains of type A
what can cause gastroenteritis?
norovirus
rotavirus
other microbes
gastroenteritis transmission
fecal-oral
gastroenteritis pathogenesis
destroys epithelium of small intestine
interferes with secretion and absorption of fluid and nutrients
What is R0?
reproductive ratio
how many people one person can infect
What is SI?
series interval
period of time from first symptoms of person 1 to first symtoms of person 2
which cells does SARS-CoV-2 target?
Type II pneumocytes
what are signs and symptoms of Covid-19?
dyspnea (SOB, increased respiration rate)
hypoxemia
productive cough
fever
tachycardia
systemic inflammatory response syndrome
hypotension
multisystem organ failure
