Parasites

Question 1

define: parasite

Answer 1

gains off of host, to host’s detriment

Question 2

describe: protists

Answer 2

unicellular eukaryotes

Question 3

describe protists, in terms of parasitic activity

Answer 3

often parasites

usually require invertebrate and mammalian host

Question 4

how many plasmodium species cause malaria in humans; whats the most important

Answer 4

5

plasmodium falciparum

Question 5

describe plasmodium falciparum life cycle

Answer 5

sporozoites injected by infected mosquito
travels through bloodstream to liver; divides to form merozoites
merozoites go into RBC’s, divide and cause RBC burst

Question 6

role of spleen

Answer 6

P.f passes here
attaches by p.f erythrocyte membrane protein to endothelium, enabling sequestration
however B cells neutralise the protein

Question 7

how does P.f overcome neutralisation of PFEM1

Answer 7

encoded by var gene, which ahs 60 variants; expressed at different points in to life cycle of plasmodium falciparum

Question 8

what is the name of the trypanosome causing african sleeping sickness

Answer 8

trypanosoma brucei

Question 9

describe trypanosoma brucei lifestyle

Answer 9

tsetse fly is infected by infected human
infected saliva injected into new human
T.b gets into bloodstream (extracellularly); B cells secrete antibodies against variant surface glycoproteins, leading to T.b death

Question 10

describe variant surface glycoproteins

Answer 10

genes found in 2 places

• internal: not expressed
• telomeric: expressed

each produces an antigenically unique VSG

one expressed at a time (allelic exclusion)

Question 11

how does the trypanosoma brucei overcome being neutralised by antibodies

Answer 11

VSG switching occurs - another gene activated, hence another VSG is made, so immune system has to respond all over agian.

Question 12

what are the 3 mechanisms of VSG switching?

Answer 12

gene conversion (telomeric replaced by internal)
telomere exchange: homologous recombination
in situ switch: telomeric gene being expressed changes