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MED-109 Biology II > topic 7B: fungi > Flashcards

topic 7B: fungi Flashcards

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1
Q

what are the two types of fungi?

A

(1) unicellular: such as yeasts (e.g. Saccharomyces cerevisiae)
(2) multicellular: e.g. mushrooms and molds

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2
Q

mushrooms and molds are types of?

A

multicellular fungi

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3
Q

regarding fungal morphology; what does the cell wall consist of?

A

chitin

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4
Q

some fungal species experience dimorphism, which is?

A

some fungi can grow both as filaments (multicellular) or yeasts (unicellular)
(depending on their environmental conditions, e.g. Blastomyces)

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5
Q

describe unicellular fungi (yeasts)

A
  • usually form multicellular colonies
  • reproduce by sexual or asexual reproduction (e.g. budding)
  • example: Saccharomyces cerevisiae
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6
Q

describe multicellular fungi

A
  • have a filamentous structure: consists of mycelia
  • have filaments: called hyphae
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7
Q

what is mycelia? what function does it have?

A
  • networks of branched hyphae (filaments)
  • function: aids in nutrient absorption
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8
Q

the hyphae of most fungi are divided into cells by internal walls called?

A

septa

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9
Q

what are the types of hyphae?

A

(1) septate = with septa
- most fungi have hyphae divided into cells by septa
- pores allow cell-to-cell movement of organelles

(2) coenocytic fungi = aseptate
- lack septa
- have a continuous cytoplasmic mass with hundreds/thousands of nuclei

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10
Q

what are septa?

A

rings of hyphae cell walls
(function: divide hyphae into cells)

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11
Q

what are the ways asexual reproduction of fungi takes place?

A

(1) simple cell division (binary fission)
(2) budding: a new organism develops from an outgrowth (bud) that separates from the parental cell

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12
Q

what are sporangia?

A

spore-producing structures

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13
Q

describe sexual reproduction of fungi

A

production of diploid zygote (2n) from the fusion of 2 haploid (n) fungi (hyphae)

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14
Q

describe fungi reproduction

A

fungi reproduce by sexual or asexual reproduction by producing spores

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15
Q

the haploid (n) spores can be produced in 2 ways:

A

sexually or asexually

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16
Q

describe how haploid (n) spores can be produced sexually?

A

sexual reproduction:
- from the zygote by meiosis
- called sexual spores
- zygote (2n) => meiosis => spores (n)

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17
Q

describe how haploid (n) spores can be produced asexually?

A

asexual reproduction:
- by mitosis
- called asexual spores
- spore (n) => mitosis => spore (n)
(haploid spores produce even more haploid spores through mitosis)

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18
Q

what is the difference between haploid spores produced by sexual and asexual reproduction?

A

they are the same spores, just produced differently

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19
Q

what is another type of reproduction that fungi can undergo?

A

germination

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20
Q

what is germination?

A
  • when, under favorable conditions, spores grow back to the vegetative cell (fungal cell)
  • spore => germination => vegetative cell
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21
Q

which of the two is ALWAYS sporogenic: fungi or bacteria?

A
  • ALL fungi is sporogenic
  • only some bacteria is sporogenic
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22
Q

describe the fungal life cycle, undergoing sexual reproduction

A

(1) a mycelium fuses with another mycelium with the process of plasmogamy (cytoplasmic fusion) initially
(2) after the cytoplasms fuse, it goes through a heterokaryotic stage (2 different haploid nuclei that do not fuse right away)
(3) then the nuclei fuse together to cause karyogamy (nuclear fission) to create the diploid zygote
(4) the diploid zygote undergoes meiosis to produce haploid spores (called sexual spores as they are produced by sexual reproduction - meiosis)
(5) these spores undergo germination when found in optimum conditions (such as in the human body) to create mycelium
(6) these mycelia can fuse together to repeat the process

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23
Q

describe the fungal life cycle, undergoing asexual reproduction

A

(1) haploid mycelium can itself undergo mitosis (asexual reproduction) and produce in the sporangia even more haploid cells
(2) again, through germination can lead to formation of mycelium (process repeats)

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24
Q

2 haploid mycelia fuse together to create a diploid zygote

A

sexual reproduction of fungi

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25
Q

the process of producing a haploid cell through mitosis is ONLY present in?

A

only plants, protists, and fungi, and NOT IN ANIMALS

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26
Q

fungi nuclei are normally _____?

A

haploid

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27
Q

what do we have instead of genders in fungi?

A
  • different mating types
    sexual reproduction = fusion of hyphae from different mating types
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28
Q

what are the sexual signaling molecules fungi use to communicate their mating type?

A

pheromones

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29
Q

what is plasmogamy?

A

the union of cytoplasm from two parent mycelia

30
Q

what is a heterokaryon?

A

the mycelium in which the haploid nuclei from each parent co-exist (they do not fuse right away)

31
Q

what is karyogamy?

A

fusion of the haploid nuclei => production of diploid cells (the zygote)

32
Q

which type of fungi prefers asexual reproduction?

A

yeasts and molds

33
Q

describe the reproduction of yeasts and molds

A
  • yeasts: reproduce mostly by asexually by simple cell division and budding
  • molds: produce haploid spores by mitosis (e.g. conidia) => form mycelia
34
Q

what are molds and yeasts are called?

A

deuteromycetes (imperfect fungi)

35
Q

what is conidia?

A

a type of asexual reproductive spore of fungi

36
Q

what supergroup does fungi belong to?

A

Opisthokonts, Unikonts

37
Q

what forms the Opisthokonts?

A

fungi, animals, and their protist relatives

38
Q

what are the 5 fungal phyla?

A
  • chytrids
  • zygomycetes
  • glomeromycetes
  • ascomycetes
  • basidiomycetes
39
Q

what is the type of spores in chytrids?

A

zoospores (flagellated spores)

40
Q

zygomycetes are named after their characteristic?

A

zygosporangia

41
Q

what is an example of a zygomycete?

A

black bread mold

42
Q

what are the spore-producing structures in zygomycetes?

A
  • sporangia
  • zygosporangia
43
Q

describe the spore-producing structures in zygomycetes

A

(1) sporangia:
- produce spores by asexual reproduction (by mitosis)
(2) zygosporangia:
- contain sexually produced spores (by karyogamy and meiosis)
- resistant to freezing and drying => can survive under unfavorable conditions

44
Q

how is zygosporangia produced/structured?

A
  • 2 different mycelia share one sporangium between them
  • these mycelia fuse to produce zygosporangia
45
Q

what are the ways ascomycetes can produce spores?

A

both sexually and asexually

46
Q

what are the spore-producing structures in ascomycetes?

A

(1) asci
- produce sexual spores (ascospores) by meiosis
- located in the ascocarps (fruiting body)
(2) conidiophores
- specialized hyphae that produce asexual spores (conidia)

47
Q

what is the fruiting body?

A

multicellular structure (reproductive structure) which contains the spore-producing structures

48
Q

what are examples of ascomycetes?

A

bread mold Neurospora crassa, morels and truffles

49
Q

what are basidiomycetes characterized as?

A

club fungi: characterized by a clublike structure called basidium

50
Q

what are the spore-producing structures in basidiomycetes?

A

basidia

51
Q

what do basidia produce?

A

produce sexual spores (basidiospores)

52
Q

what is basidiocarp?

A

the fruiting body, has numerous basidia

53
Q

what are examples of basidiocarp?

A

mushrooms (the fruiting body = reproductive structure of basidiomycetes

54
Q

which of the 5 fungal phyla is the only type that does not produce asexual spores?

A

basidiomycetes, only produce sexual spores

55
Q

fungi have several interactions with other organisms:

A
  • decomposers
  • mutualists
  • parasites
56
Q

what are the examples of plant pathogenic fungi?

A

(1) pathogenic zygomycetes
(2) pathogenic ascomycetes
(3) pathogenic basidiomycetes

57
Q

describe pathogenic zygomycetes

A
  • ex: genera Mucor, Rhizopus, Absidia
  • cause skin and ear infections, bronchitis-pneumonia
58
Q

describe pathogenic ascomycetes

A

(A) Aspergillus flavus:
- produces mycotoxins such as aflatoxins
- infects peanuts and wheat
- causes Aflatoxin B1: which causes liver cancer due to p53 mutations
(B) Claviceps purpurea:
- infects cereals (e.g. rye)
- produces ergotamine and lysergic acid (precursors for LSD synthesis)
=> psychotropic effects (hallucinations, temporary insanity), convulsions, gangrene

59
Q

describe pathogenic basidiomycetes

A

(A) Amanita phalloides
- poisonous mushrooms
- contain lethal toxins (e.g. phalloidin, amanitin)
(1) α-amanitin: inhibits eukaryotic RNA polymerase II
(2) phalloidin: inhibits F-actin poymerization

(B) Amanita muscaria ands Psilocybe cubensis
- magic mushrooms
- psychoactive mushrooms => cause hallucinations (psychotropic effects)

60
Q

what effect does the lethal toxin α-amanitin have?

A

inhibits transcription of mRNA, which inhibits gene expression (death)

61
Q

what effect does the lethal toxin phalloidin have?

A

inhibits many cell functions, and the polymerization/depolymerization of actin

62
Q

what are mycoses?

A

human fungal infections

63
Q

what are the major types of human mycoses?

A
  • superficial-cutaneous mycoses (IMP)
  • subcutaneous mycoses
  • systemic mycoses
  • opportunistic mycoses (IMP)
64
Q

describe superficial-cutaneous mycoses

A

fungal infections of hair, nails, and skin

65
Q

what are the examples of superficial-cutaneous mycoses?

A

(1) Microsporum furfur
- ascomycete that causes ringworm

(2) Ascomycete genera Trichophyton and Epidermophyton
- causes athlete’s foot (ringworm of the foot

66
Q

describe opportunistic mycoses

A
  • caused by fungi that are part of our normal flora (saliva, skin, digestive system)
  • normally non-pathogenic
  • become pathogenic and cause infections only in immunosuppressed individuals
67
Q

what are the examples of opportunistic mycoses?

A

yeast Candida albicans
- causes candidiasis
=> mouth infection (thrush), skin infection, vaginal infection

68
Q

what are some industrial and therapeutic applications of fungi?

A
  • production of antibiotics
  • production of alcoholic beverages, bread and cheeses
  • genetic engineering
69
Q

what are the examples of fungi production of antibiotics?

A

ascomycetes of genus penicillin
(1) penicillium chrysogenum
- produces penicillin (anti-bacterial antibiotic)
(2) penicillium griseofulvum
- produces griseofulvin (anti-fungal antibiotic)

70
Q

what are the examples of fungi production of alcoholic beverages, bread and cheeses?

A

ex: the yeast Saccharomyces cerevisiae:
- production of enzymes used for alcohol fermentation => production of beer, wine, etc
- also used as baking yeast

71
Q

what are the examples of fungi in genetic engineering?

A
  • ex: insulin-like growth factor (IGF) can be produced in the fungus Saccharomyces cerevisiae
  • study of genes involved in human diseases

MED-109 Biology II (10 decks)

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