viruses as causes of disease

Question 1

describe the structure of a virus

Answer 1

outer protein coat (capsid)
strand of nucelic acid either DNA or RNA
do not have membranes or any organelles (non-cellular structures)

Question 2

Why are viruses obligate intracellular parasites?

Answer 2

as they require the organelles and enzymes of a host to carry out metabolic reactions to make their protein coat etc

Question 3

What are the living components of viruses?

Answer 3

nucleic acid
protein coat
can replicate inside cells and pass on genetic info

Question 4

What are the non-living components of viruses?

Answer 4

non-cellular
cannot reproduce by themselves 
do not have cell organelles 
have only one type of nucleic acid 
do not feed or respire

Question 5

what are the components of a virion?

Answer 5

lipid envelope
protein capsid
virion associated polymerase
nucelic acid 
spike projections (cell receptors)

Question 6

What are the two main types of shapes of viruses?

Answer 6

helical

icosahedral

Question 7

what are the stages of viral replication?

Answer 7

attachement 
cell entry 
interaction with host cells 
replication
assembly 
release 
ACIRAR

Question 8

what are the five key ways that viruses cause disease?

Answer 8

damage by direct destruction of host cells
modification of host cell structure or function
over-reactivity of the host
cell proliferation and cell immortalisation
evasion of host defence

Question 9

Give an example of a lab technique that used direct destruction of host cells as a diagnostic tool?

Answer 9

the cytopathic effect seen under a light microscope

Question 10

Give an example of a virus that causes damage by modification of host cell structure and function

Answer 10

rotavirus - shortening and atrophy of villi, flattening of epithelial cells and denuding of microvilli, decreases SA< causes malabsorption and therefore diarrhoea by osmosis

Question 11

give an example of a virus that results in over-reactivity of the host

Answer 11

HepB as in acute infection there is a massive Ab and cytotoxic T cell response that damages liver cells

Question 12

give an example of a virus that causes damage by cell proliferation and immortalisation

Answer 12

HPV

Question 13

describe some serological techniques to detect viruses

Answer 13

detection of viral Ag/Ab through ELISA

serological profile of Ab - testing for IgG or IgM, to see whether acute or chronic infection

Question 14

which Ab can pass through the placenta?

Answer 14

IgG

Question 15

what is the disadvantage for testing for IgM?

Answer 15

IgM may not be detected at the time the test is done, even if there is an acute infection as it takes time for Abs to be produced

Question 16

List the methods for detecting viral infection

Answer 16

cytopathic effect
electron microscope 
ELISA for Ab/Ag
serology for IgG/IgM
PCR