Viruses (DOLT) Flashcards
commonality between viruses and bacteria
affect on human health
living or non-living
some believe they are living but they don’t meet all the requirements to be considered living organisms
size
discovered around 100 years ago because they are so small. around 1/100th size of bacteria
where are they found?
every ecosystem
structures
interior- long strand of genetic material
extensions- allow viruses to attach to other cells
some have an additional coating made up of lipid molecules
genetic material
DNA or RNA surrounded by protective coat of protein
structural shapes
helical
circular
polyhedral- multisurfaced
complex
internal organelles
no internal organelles
energy
no mitocondria or chloroplasts
can’t create or use energy
protein synthesis
no ribosomes
cytoplasm
no
consumption and excretion
don’t consume anything or produce any waste
motility
not motile
virus structures
surface proteins, capsid, genetic material, viral envelope
classification
shape, type of genetic material, or type of organism/tissue they infect
bacteriophages “phages”
viruses that can infect bacteria and kill them
useful in search for vectors for genetic engineering
Felix D’Herelle
Canadian scientist
discovered phages
researched ways to cholera and typhoid with viruses
research halted when penicillin was discovered
viral reproduction
can only reproduce inside a living host/cell
infected by a virus
virus is inside your cells and reproducing to create more viruses and infect more cells
create a “virus factory”- cells can no longer perform their usual functions
last step in reproduction is splitting the cell open and releasing 1000s of new viruses
ways for a virus to enter a cell
- cell engulfs virus like an amoeba engulfs its food
- protein layer of virus fuses with the host cell’s membrane
- DNA viruses- inject genetic material into cytoplasm
- RNA viruses- have an enzyme that converts RNA to DNA then injects it into cytoplasm
reproduction cycles
lytic and lysogenic
lyric cycle
actively causing a disease
starts when virus is engulfed into host cell or fuses to it
viral DNA becomes part of host DNA and host used its own enzymes to help viruses reproduce
host’s ribosomes make protein for viruses
cycle continues as viruses continue to be engulfed or fuse
making a new virus
protein and DNA is assembled during lytic cycle
lyses
when a cell splits open because it is too full of viruses
lysogenic cycle
not actively causing a disease
turns into lytic cycle when environmental factors trigger DNA into taking control of the cell
after DNA is injected into the host cell nothing happens during the lysogenic cycle
examples of viral diseases
common cold, influenza (flu), measles, mumps, rhubella, chicken pox, hepatitis, rabies, polio, small px, HIV
vulnerability factors for viral diseases
very young, elderly, imunocompromised people, people who are already sick
least vulnerable
healthy young-middle aged adults
recovery from viral diseases
depends on virus
some are more dangerous than others
vulnerability factors affect the seriousness of it and the likelihood of recovery
childhood diseases
exception to vulnerability factors
much more serious for adults than children
adult males can become sterile because of mumps
ex. mumps. measles, chicken pox
ways to spread viral diseases
airborne, bodily fluids, touch
spread airborne
coughing and sneezing
breathe the viruses in
spread through bodily fluids
blood, saliva, urine, semen
sharing food and drinks
ex. STDs
spread through touch
rubbing eyes after touching something that has a virus on it
open cuts or sores
lifetime outside of a living host/cell
not very long
rely on their host to survive
mechanical barriers
first line of defense against both viral and bacterial diseases
skin, nose, tears
skin
unbroken skin blocks disease
broken skin provides a way for diseases to enter the body
nose
lined with cilia that use mucus to trap incoming viruses
sneeze when there is a build-up of mucus which gets rid of the viruses
tears
salty- creates an unfavourable environment
when eyes are irritated they become watery and wash the irritant away
second line of defense against disease
cellular
white blood cells
converge at site of infection and engulf bacteria or viruses
die when they are too many inside them
lysosomes
destroy bacteria or viruses with an enzyme after white blood cell engulfs it
pus
mix of dead white blood cells, viruses and bacteria
histamines
cause swelling and redness
cells near infection release histamines to dialate blood vessels- increase supply of white blood cells
allergic reactions
cause cells to release histamine
anti-histamines counter it
Helper T cells
produced by thymus gland (located under sternum)
direct the immune system response
Killer T cells
released from thymus gland by Helper T cells
kill cells infected with viruses to prevent them from splitting
B cells
Helper T cells activate 2 types: plasma and memory
‘b’ stands for bone marrow
responsible for immunity
fevers help produce them
Suppressor T cells
returns body back to normal after infection
interferon
protein released by cells interacting during an infections
speed up action of T cells and B cells
Human Interferon is produced by genetic engineering
antibodies
final line of defense
y shaped molecules
attach to viruses and destroy them
can prevent viruses from infecting more cells
antigens
projections on viruses that antibodies use to connect to them
production of antibodies
produced by plasma B cells
memory B cells
“remember” antigens
produce the correct antibodies immediately
immunity
means you will not contract a certain disease
different types: genetic or exposure
immunity in babies
get antibodies from their mothers through the placenta and breast feeding
lose their immunity because memory B cells aren’t created and antibodies don’t last for a long time
injections of antibodies
temporary immunity
done during epidemics for medical personnel and essential service workers
isolated from donated blood
permanent immunity
2 ways:
- having the disease: memory B cells are created as your body fights the illness
- vaccines: trick the body into believing its had the disease and creates memory B cells
vaccines
injections of dead or weakened viruses
only effective if virus doesn’t change or mutate
sometimes feel a little ill after getting one
Edward Jenner
discovered the first vaccine in 1796
injected cow pox into a child and then small pox after the child recovered and the child did not develop small pox
not being vaccinated
some people are opposed to them based on religious, safety, personal choice, and ethical grounds
some people can be allergic to the eggs used to create vaccines (tend to be other options available)
fewer people vaccinated=higher risk of epidemic
link between vaccines and autism
published by Andrew Wakefield in 90s
many children were no vaccinated in response
2011- Wakefield lost his license for falsifying the research (too late for many children)
2019- many epidemics of measles in different countries
the flu
airborne RNA virus
spreads across the world every year and varies in severity
symptoms: chills, fever, muscle and joint pain, headache, coughing, runny nose, sore throat
sunlight, detergents and disinfectants kill it
vaccine for the flu
based on the WHOs prediction of what strains will be present in the next year
some years it is more accurate than others
takes 2 weeks to take effect
what the flu infects
birds and mammals (not just humans)
cross from one species to another through mutation
Spanish flu
1918-19 after WWI
most severe flu outbreak ever reported
“Spanish” because Spain reported the most openly about the symptoms and severity
~100mil people were killed (more than in the war)
killed the young-middle aged healthy adults
caused overactivity of immune system
H1N1 virus
2009 outbreak
better controlled
~300.000 deaths
HIV
human immunodeficiency virus
causes AIDS (acquired immunodeficiency syndrome)- disease in the human immune system
transmitted through blood, unprotected sex, placenta, childbirth, breast feeding, contaminated needles, blood transfusions
not transmitted through saliva or tears, or other bodily fluids
RNA virus- can undergo a lysogenic cycle and remain dormant for years
attacks Helper T cells
people with AIDS have lowered immune system
no cure or vaccine
ARVs
slow progress of HIV/AIDS and increase life expectancy
very expensive
required for the rest of the person’s life
many side effects
