microbial infection

Question 1

• Why are viruses not cells in their own right and what are they, if not cells?
• List the main types of infectious agent causing disease in humans

Answer 1

Obligate parasites, require a host cell

Virus, Fungi, Bacteria, Protozoa, Helminth

Question 2

• Describe how viruses replicate

- What makes HIV a retrovirus?

Answer 2

Use host cell machinery
divide by budding out of cell- cytolysis

usually viruses use DNA to make RNA which makes proteins
but HIV uses RNA to make DNA using reverse transcriptase

Question 3

• What makes Prokaryotes more susceptible to the effects of a mutation?

Answer 3

They are haploid, so if one gene is mutated, the effect will occur
However in diploid cell, the mutation must be seen on both copies of DNA to occur

Question 4

• What are the purpose of the pili (several pilus) on Prokaryotes
• Why are the mutation rates of viruses higher than humans?

Answer 4

Mainly adherence, a key virulence factor, helps infection
also helps with movement

they have error prone replication, shorter replication time
therefore half the point mutation rate

Question 5

• What three types of mycoses do fungi give rise to?

- Which two forms can fungi exist in during their lifetimes?

Answer 5

Cutaneous- skin, hair, nails
Mucosal- oral, vaginal
systemic mycoses - internal organs

yeast (unicellular, asexual) filaments (multicellular, asexual and sexual)
yeast bud or divide
filaments have cross walls or septa

Question 6

• How do Protozoa replicate?
• How is Protozoa infection acquired?
• What does Metazoa mean?
• What type of organisms are Helminths?

Answer 6

form trophozoites in cell
or divide by binary fission

ingestion or through vector

they contain cells differentiated into tissues and organs

multi cellular and eukaryotic eg tapeworm flatworm

Question 7

Differences between protozoa and eukaryotes

Answer 7

protozoa have no internal membrane, eukaryotes do
divide by binary fission
peptidoglycan cell wall
haploid
cytoskeleton is poorly defined

Question 8

where is the life cycle of a helminth

give examples of protozoa diseases

Answer 8

outside human hosts

Malaria, Leishmaniasis

Question 9

how do food allergies occur

Answer 9

if an allergen is ingested

act on mucosal mast cells in the intestinal tract

stimulation of smooth muscle leads to vomiting and diarrhoea

allergic substance can be absorbed and pass into the bloodstream, causing skin symptoms