Lecture 3 Study Questions

Question 1

How are fungi different from plants and animals?

Answer 1

Plants have chlorophyll thus they photosynthesise, whereas fungi don’t have chlorophyll and don’t photosynthesise.
Animals don’t have a cell wall, whereas fungi does.

Question 2

How do yeast differ from moulds?

Answer 2

Moulds have mycelial growth made up of branching tubular filaments called hyphae.
Yeast are unicellular organisms larger than bacteria, but still require a microscope for vision

Question 3

What is a dimorphic fungus?

Answer 3

A fungus that can be yeast or mycelial (mould) depending on the environment.

Question 4

What media is used of growing fungi?

Answer 4

Sabouraud’s agar–> high sugar conc, acidic pH and antibiotics (suppress bacterial growth)

Question 5

Why are oranges spoilt by mould rather than bacteria?

Answer 5

Oranges have more requirements of fungal growth as compared to bacterial growth: acidic pH, moist surface and when kept in room temp, a temp of 25-30C. It also a high conc of sugar which the fungi feeds on while growing.

Question 6

List the types of asexual spores of fungi.

Answer 6

1) sporangiospores: spores inside a sac called spornagium.
2) chlamydospores: spores within thickened cell wall of hyphae
3) conidiospores (conidia): naked spores in chains at hyphae tip
4) blastospores: form as buds

Question 7

List the four stages of fungal asexual spore formation.

Answer 7

1) cells of + thallus and - thallus fuse to form dikaryotic stage (have 2 separate genes and chromosomes)
2) after several hrs/yrs/centuries nuclei fuse (diploid state)
3) meiosis of nucleus restores haploid state
4) haploid state is then partitioned into + and - spores

Question 8

List the three types of sexual spores.

Answer 8

1) zygomycota–> zygospores, zygosporangia
2) basidiomycota–> basidiospores
3) ascomycota–> ascospores

Question 9

Name one dermatophyte that causes tinea.

Answer 9

Trichophyton mentagrophytes (or T. Rubrum)

Question 10

Sporotrichosis is caused by which fungus?

Answer 10

Sporothrix schenckii

Question 11

Systemic mycoses are caused by which fungi?

Answer 11

1) histoplasmosis: H. capsulatum
2) blastomycosis: B. Dermatitidis
3) coccidiomycosis: Caccidiodes immitis
4) paracoccidiodomycosis: Paracoccidioides brasiliensis

Question 12

Candidosis, crytococcosis and pneumosystis pneumonia are diseases caused by opportunistic fungi. True of false?

Answer 12

True

Question 13

Mycotoxins contaminate approximately 25% of foods world wide, however usually do not cause disease, why?

Answer 13

Because they are only present in the food at very low levels.

Question 14

Why can’t viruses by grown on artificial media?

Answer 14

Because they lack their own metabolic machinery and thus require living cells to grow.

Question 15

What is the main feature of viruses that is used to classify them?

Answer 15

The genetic material of viruses is the main feature that is used to classify them.
Viruses can either be DNA viruses or RNA viruses.

Question 16

What two main viral symmetries do viruses causing human diseases have?

Answer 16

Most human viral infections are caused by viruses that have: iscosahedral or helical symmetries.

Question 18

What two ways that viruses can cause disease?

Answer 18

1. Replication within host cell leading to direct damage of the cell .e.g. HIV
2. Host defences leads to cell damage as it attempts to clear the virus infected cells.

Question 19

List the stages of viral infectivity.

Answer 19

1. Attachment: to host cell via specific receptor on cell membrane.
2. Penetration: entry into host cell & uncoats caspid
3. Replication of viral genome: production on viral mRNA & early early viral proteins
4. Production of late viral proteins
5. Assembly of progeny virions
6. Release of virions from cell (either by budding or lysis of cells)

Question 21

List the methods of viral control.

Answer 21

1) heat
2) ether
3) disinfectants e.g. Glutaraldehydes, hypochlorites
4) UV light
5) anti-viral drugs
6) vaccines e.g. Smallpox has been eradicated by vaccines

Question 22

What is the basic structure of viruses?

Answer 22

• it has a nucleic acid core (DNA or RNA)
• surrounded by a protein shell called a caspid made out of capsomeres
• can be with or without envelope
• and envelope can be with or without spikes

Question 23

List the modes of transmission of viruses.

Answer 23

• physical contact (direct or indirect)
• airborne ( sars and influenza)
• food-borne (food or water)
• anthropod-borne (antrhopods- insects)

Question 24

What are the names for round and flat worms?

Answer 24

Nematodes: round worms
Platyhelminthes: flat worms

Question 25

Trichinella spiralis is found in what type of food?

Answer 25

Pig meat- must cook pork adequately

Question 26

What is the common name for cestodia?

Answer 26

Tape worms

Question 27

Why are nematode infections so common?

Answer 27

Because most nematodes have a faecal oral transmission via water and contaminated hands (esp. through children).

Question 28

What are the symptoms of Malaria and why do these symptoms occur?

Answer 28

Chills, fever, nausea and headache.

Occur due to the lysis of RBCs

Question 29

Ascaris lumbricoides,Trichuris trichiura and Enterobius vermicularis are what type of helminth?

Answer 29

Nematodes (round worm)

Question 30

What is the main rout of infection for parasites? What is an exception?

Answer 30

Food and Faecal-oral route except malaria (protozoan infection) which is spread via insect bites on humans

Question 31

List the methods of detecting viruses for diagnostic purposes.

Answer 31

• electron microscopy
• fluorescent microscopy
• serological tears (blood sample)
• isolation of virus on cell or animal cultures
• nucleic acid detection via PCR (main method)

Question 32

What is a “prion”?

Answer 32

Group of organisms, similar to viruses. These are proteinacious infections particles (prions) that result in abnormal protein conformation which changes the conformation of other normal proteins of the same kind–> disease!