Module 3 - Viruses and Fungi Flashcards

1
Q

What is the fundamental structure of every virus?

A

A nucleic acid (DNA/RNA) surrounded by a capsid

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2
Q

What is different between a virus’ extracellular and intracellular states?

A

Extracellular: metabolically inert; stable structure which protects genome
Intracellular: stable protective capsid breaks down; redirects host machinery - reliant on host cell metabolism

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3
Q

What are the two kinds of symmetry viruses can show?

A

Helical symmetry, and isocahedral (5-3-2) symmetry

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4
Q

Name the 6 stages of the virus replication cycle

A

Attachment, Penetration, Uncoating, Synthesis, Assembly, Release

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5
Q

Name the process(es) by which viruses generally and leave a host cell?

A

Enter by endocytosis, Exit by budding

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6
Q

What happens during the uncoating phase of a virus life cycle?

A

The protective capsule breaks down so that the viral genome can be released into the cell

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7
Q

How do viruses leave an animal cell?

A

Enveloped viruses generally leave via exocytosis, taking a part of the cell membrane with them; naked viruses often simply lyse the cell and are released

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8
Q

What type of nutrition do fungi show?

A

They are organoheterotrophs - they break down polymers outside of the cell using hydrolytic enzymes)

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9
Q

Name the 5 major phyla of kingdom fungi

A

Basidiomycota, Ascomycota, Glomeromycota, Zygomycota, Chytridiomycota

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10
Q

Describe the structure of chytridiomycota

A

Aquatic fungi with flagellated, motile, asexual and sexual spores; have a single large thallus containing motile zoospores, and from which rhizoids emerge

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11
Q

Describe the structure of zygomycota

A

Terrestrial fungi with non-motile, asexual spores (found in sporangium); have a large sexual zygospore

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12
Q

Describe the structure of ascomycota

A

Produces aerial-borne chains of asexual conidiospores; 8 sexual ascospores are contained in a single ascus -> asci borne on ascocarp

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13
Q

Describe the structure of basidiomycota

A

Form mushrooms and toadstools; usually form 4 sexual basidiospores on a club-like structure called the basidium; the basidia line the gills or pores of the mushroom

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14
Q

What determines whether Dimorphic fungi are in a yeast or filamentous form?

A

Temperature: (e.g., for some, 37C = yeast, 20-25C = filamentous)

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15
Q

Describe how unicellular fungi grow

A

Budding - a form of asexual reproduction. (A new organism grows from a bud/outgrowth on a parent cell, remaining attached as it grows, and only separating once it is mature)

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16
Q

Describe how filamentous fungi spread

A

From a mat of hyphae, aerial hyphae grow up, and form sexual spores called conidia

17
Q

Name the two types of Hyphae structure in terms of separate cells

A

Septate (cells separated by septa) or coenocytic (single, multinucleated cell)

18
Q

Describe the structure of chitin

A

Polymer of N-acetylglucosamine; forms microfibrillar bundles

19
Q

Which fungal hypha is most primitive and why?

A

Chytridiomycota - they are the only phylum to still possess a flagella

20
Q

What type of growth occurs in hyphae, and what advantage does this provide?

A

Apical growth - gives penetrating power

21
Q

What processes/forces power growth of hyphae?

A

Actin polymerisation; cytoplasmic expansion forces

22
Q

What is the Spitzenkorper?

A

A cluster of micro-vesicles (chitosomes) and macrovesicles, embedded in a meshwork of actin filaments

23
Q

What do the vesicles in the Spitzenkorper contain?

A
  • Enzymes involved in cell wall biosynthesis
  • Enzyme activators GTP and Protease
  • Enzymes involved in cell wall lysis
  • Pre-formed wall polymers e.g., Mannoproteins
24
Q

What 3 things do NOT apply to viruses? (Sorry weirdly phrased question)

A

They are NOT alive, canNOT generate ATP and do NOT have ribosomes

25
Q

What IS a virus?

A

A small, infectious, obligate intracellular parasite

26
Q

What is the usual size range of viruses?

A

20 nm to 1.5 µm

27
Q

Which are the only group of viruses that are big enough to be seen without an electron microscope?

A

Those that infect Amoebozoa

28
Q

Ultrastructure of Tobacco Mosaic Virus?

A

Helical, +ssRNA genome, naked (i.e. no envelope)

29
Q

Ultrastructure of Adenoviruses?

A

Icosahedral, DNA genome, glycoproteins on surface of capsid

30
Q

What are the two types of viruses that can have both DNA and RNA genomes depending on the stage of the replication cycle?

A

Retroviruses (e.g., HIV) and Hepadnaviruses (e.g., HepB)

31
Q

How do retroviruses replicate?

A

They have an RNA genome but replicate via a DNA intermediate, then use reverse transcriptase to translate their RNA into DNA in the host cell

32
Q

How do hepadnaviruses replicate?

A

DNA genome which replicates via an RNA intermediate

33
Q

What are viral capsids?

A

A protein coat or shell made up of capsomere units - can be a polymer of a single protein (e.g., in parvovirus) or several proteins (e.g., adenovirus, smallpox)

34
Q

Name 3 ENVELOPED viruses (i.e. surrounded by a membrane as well as capsid)

A

Influenza, Coronavirus, Herpes

35
Q

What happens during the latent period on a viral one-step growth curve?

A

Adsorption, Eclipse and Maturation
(Synthesis of early enzymes, nucleic acids and protein coats must take place)

36
Q

How long does the whole process from Adsorption to Release take for bacteriophages and for animal viruses?

A

30-60 minutes for phages, 8-40 hours for animal viruses

37
Q

What are the three (general) distinct regions of growing hyphae?

A

Apical region, Subapical region and Vacuolation Zone

38
Q

Name the layers of the fungal cell wall

A

(Moving outward from cell membrane) Chitin; ß1-3 and ß1-6-glucan; Mannoproteins