Viruses, Viroids, Prions & Prokaryotes – Review Flashcards

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A comprehensive set of flashcards covering viruses, viroids, prions, emerging diseases, and prokaryotic biology (bacteria and archaea).

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89 Terms

1
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What genetic material do viruses possess?

Either DNA or RNA, never both.

2
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Can viruses evolve?

Yes, viruses can evolve over time.

3
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Why are viruses called obligate intracellular parasites?

Because they can replicate only inside a host cell.

4
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Who coined the term “virus” and in what year?

Louis Pasteur in 1884.

5
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What does the Latin word ‘virus’ mean?

Poison.

6
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What key finding did Ivanowsky make in 1892 about tobacco mosaic disease?

Filtered sap free of bacteria could still cause the disease, implying an agent smaller than bacteria.

7
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Why is viral classification difficult?

Viruses mutate rapidly and are not considered living organisms.

8
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List the taxonomic levels used for viruses.

Order, family, genus, species.

9
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Roughly how many viral species are known today?

More than 2,500.

10
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What system is used to classify new variants within the same viral species?

Subtypes (e.g., H and N types in influenza).

11
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Name the two main structural parts of a virus particle.

Covering and inner core.

12
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What does a viral covering include?

Protein capsid and, in some viruses, a lipid envelope.

13
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What is found in the inner core of a virus?

Nucleic acid (DNA or RNA) and viral proteins/enzymes.

14
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Define viral capsid.

The protein coat made of repeating protein subunits.

15
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What is a viral envelope and its origin?

A lipid membrane surrounding some viruses; it is derived from the host cell membrane.

16
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What are viral glycoproteins?

Proteins encoded by the viral genome that protrude from the envelope and aid in attachment.

17
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What is a naked virus?

A virus lacking an envelope.

18
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Describe the structure of Tobacco Mosaic Virus.

RNA virus with a helical capsid.

19
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Describe the structure of a T-even bacteriophage.

DNA virus with a polyhedral head and helical tail with fibers and base plate.

20
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Describe the structure of the influenza virus.

RNA virus with spherical capsid, envelope, and surface spikes.

21
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What is host specificity?

A virus can infect only particular species or cell types.

22
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Define tissue tropism.

Restriction of a virus to specific tissues that bear the right receptors.

23
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List the five general steps of viral reproduction.

Attachment, penetration, biosynthesis, maturation, release.

24
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What happens in the lytic cycle?

The host cell is lysed, releasing new viruses and causing cell death.

25
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What is a prophage?

Latent viral DNA integrated into a host’s chromosome during the lysogenic cycle.

26
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How can a lysogenic virus become lytic?

Environmental stressors can trigger activation to the lytic cycle.

27
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During viral latency, what is occurring?

Viral DNA replicates with host DNA, but virions are not produced.

28
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Give an example of toxins produced due to lysogenic conversion.

Toxins produced in scarlet fever.

29
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How do many enveloped animal viruses enter host cells?

Fusion of their envelope with the host membrane.

30
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How do many naked animal viruses enter host cells?

Endocytosis by the host cell.

31
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What is uncoating in animal viruses?

Removal of capsid (and envelope) to release genetic material.

32
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Name a highly virulent virus that rapidly destroys host cells.

Ebola virus.

33
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How are enveloped animal viruses often released?

Budding, acquiring a host-derived envelope.

34
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How do naked animal viruses typically exit the host cell?

By causing lysis of the host cell.

35
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What are bacteriophages?

Viruses that infect bacteria.

36
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What is phage therapy?

Using bacteriophages to treat bacterial infections.

37
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What is a retrovirus?

An RNA animal virus that converts its RNA into DNA via reverse transcriptase.

38
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Give an example of a retrovirus.

HIV.

39
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Define viroids.

Naked strands of RNA with no capsid that infect plants.

40
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Define prions.

Infectious proteins with abnormal conformation causing neurodegenerative diseases.

41
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Name diseases caused by prions.

Transmissible spongiform encephalopathies (e.g., mad cow disease).

42
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What is an emerging infectious disease?

A disease appearing for the first time in humans or increasing rapidly in incidence or geographic range.

43
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List factors that drive emerging viral outbreaks.

Changes in transmission, lack of immunity, and viral mutation.

44
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Which two domains make up the prokaryotes?

Bacteria and Archaea.

45
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Who first described prokaryotes as “animalcules”?

Antonie van Leeuwenhoek.

46
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What concept did Louis Pasteur disprove?

Spontaneous generation.

47
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What did Pasteur’s swan-neck flask experiment demonstrate?

Airborne microbes contaminate broth; without contaminants, no growth occurs.

48
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Name the three main structural regions of a prokaryotic cell.

Cell envelope, cytoplasm, appendages.

49
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Components of a prokaryotic cell envelope include…

Plasma membrane, cell wall, glycocalyx.

50
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What is the bacterial cell wall made of?

Peptidoglycan.

51
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Function of the glycocalyx?

Attachment and protection from host immune response.

52
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Where is the bacterial chromosome located?

In the nucleoid region of the cytoplasm.

53
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Role of prokaryotic ribosomes?

Protein synthesis.

54
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Define fimbriae.

Short bristle-like structures for attachment to surfaces.

55
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What is a conjugation pilus?

Hollow appendage for DNA transfer between bacteria.

56
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What is the primary means of reproduction in bacteria?

Binary fission (asexual).

57
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What is horizontal gene transfer?

Transfer of genes between bacteria by non-reproductive means.

58
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Differentiate conjugation, transformation, and transduction.

Conjugation: plasmid transfer via pilus; Transformation: uptake of free DNA; Transduction: DNA transfer by bacteriophage.

59
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Purpose of the Gram stain?

To distinguish Gram-positive from Gram-negative bacteria based on cell wall structure.

60
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Describe Gram-positive cell walls.

Thick peptidoglycan layer outside the plasma membrane; stain purple.

61
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Describe Gram-negative cell walls.

Thin peptidoglycan sandwiched between inner & outer membranes; stain pink/red.

62
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Why are Gram-negative bacteria more antibiotic-resistant?

Their outer membrane blocks many antibiotics.

63
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Name the three common bacterial shapes.

Cocci (spherical), bacilli (rod), spirilli (spiral).

64
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What does ‘staph-’ indicate in bacterial arrangement?

Clusters.

65
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What does ‘strept-’ indicate?

Chains.

66
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Define aerobic bacteria.

Bacteria that require oxygen for cellular respiration.

67
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Define facultative anaerobe.

Can grow with or without oxygen.

68
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Define obligate anaerobe.

Cannot grow in the presence of oxygen.

69
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What are photoautotrophs?

Photosynthetic bacteria using light to reduce CO₂.

70
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Differentiate oxygenic vs anoxygenic photosynthesis.

Oxygenic (produces O₂, uses PSI & PSII); Anoxygenic (no O₂, uses PSI only).

71
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What are chemoautotrophs?

Bacteria that oxidize inorganic compounds and fix CO₂.

72
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What are chemoheterotrophs?

Bacteria obtaining both carbon and energy from organic molecules.

73
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Define saprotroph.

Organism that decomposes dead organic matter; many pathogenic bacteria are saprotrophs.

74
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How do bacterial toxins cause disease?

They disrupt host processes, causing symptoms like food poisoning or shock.

75
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What are LPS and why dangerous?

Lipopolysaccharides in Gram-negative walls; they overstimulate immune response, causing shock.

76
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What are superantigens?

Proteins that hyper-activate immune cells, leading to shock.

77
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Define endospore.

Highly resistant dormant structure formed inside some bacteria.

78
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Name three genera that produce endospores.

Clostridium botulinum, Clostridium tetani, Bacillus anthracis.

79
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When do endospores germinate?

When environmental conditions become favorable.

80
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What is the action of penicillins & vancomycin?

Inhibit peptidoglycan synthesis, weakening cell walls.

81
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How do tetracyclines & erythromycin act?

Bind bacterial ribosomes, blocking protein synthesis.

82
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Mechanism of sulfonamides & quinolones?

Inhibit bacterial nucleic acid synthesis.

83
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Do antibiotics harm human cells?

No; they selectively target bacterial structures/processes.

84
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Key biochemical trait distinguishing Archaea from bacteria?

Unique membrane lipids (branched hydrocarbons linked to glycerol).

85
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Do Archaea have peptidoglycan?

No.

86
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Name three major groups of Archaea.

Methanogens, halophiles, thermoacidophiles.

87
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Where are methanogens found and what do they produce?

Anaerobic habitats (swamps, intestines); produce methane from H₂ and CO₂.

88
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What conditions do halophiles require?

High salt concentrations (12–15%).

89
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Describe thermoacidophiles.

Archaea thriving in extremely hot, acidic environments such as hot springs.