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MD2001 Week 4 > Microbial Structure > Flashcards

Microbial Structure Flashcards

1
Q

What do eukaryotic and prokaryotic cells have in common?

A

Plasma membrane

Cytoplasm

DNA

Ribosomes

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2
Q

What characteristics are specific in eukaryotes?

A

True nucleus

Linear DNA

DNA organised into chromosomes

Large complex ribosomes with many types of rRNA and proteins

Cytoplasm filled with large complex collection of organelles

Mitochondria

Transcription requires formation of mRNA and movement of mRNA from nucleus to cytoplasm for translation

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3
Q

What characteristics are specific in prokaryotes?

A

No nucleus

Circular DNA

DNA naked

70S ribosome

No membrane bound organelles independent of plasma membrane

Mesosomes are used in respiration

Transcription and translation occur simultaneously

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4
Q

What are the structural features of bacteria?

A

Capsule

Pili

Flagellae

Spores

Slime

Cell wall

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5
Q

What is the bacterial capsule made from?

A

Loose polysaccharide

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6
Q

What is the function of the bacterial capsule?

A

Protects from phagocytosis

Protects cell from desiccation

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7
Q

What is pili made from?

A

Oligomeric pilin proteins

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8
Q

What is the function of pili?

A

Appendage used for bacterial conjugation

Forms tube/bridge to enable transfer of plasmids between bacteria

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9
Q

Characteristic of pili

A

Highly antigenic

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10
Q

What is flagellae?

A

Organs of locomotion

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11
Q

What is flagellae made out of?

A

Composed of flagellin protein

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12
Q

What are spores?

A

Hard, multi-layered coats making spore difficult to kill

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13
Q

What happens when a bacteria becomes a spore?

A

Metabolically inert form triggered by adverse environmental conditions

Adapted for long-term survival allowing for regrowth when conditions are desirable

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14
Q

Example of common diseases caused by spores?

A

Botulism- Clostridium botulinum

Gas gangrene-Clostridium perfringes

Tetanus- Clostridium tetani

Food poisoning- Clostridium perfringes

Anthrax- Bacillus anthracis

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15
Q

What is slime?

A

Polysaccharide material

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16
Q

What is the function of slime?

A

Protects against immune attack

Protects against eradication by antibiotics

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17
Q

How do you differentiate bacteria into two groups based on their cell wall?

A

Gram positive

Gram negative

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18
Q

What is the structure of a gram positive cell wall?

A

Thich peptidoglycan wall

Followed by a phospholipid cytoplasmic membrane

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19
Q

What is the structure of a gram negative cell wall?

A

An outer phospholipid membrane

Thin layer of peptidoglycan attached via lipoprotein

An inner phospholipid membrane

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20
Q

What are the four steps in gram staining?

A

Primary stain

Trapping agent

Decolourisation

Counterstain

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21
Q

What dye is used in the primary staining?

A

Crystal violet dye

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22
Q

What is used as the trapping agent?

A

Gram’s iodine

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23
Q

What is the outcome of the decolourisation step in gram staining?

A

Gram negative bacteria lose their lipopolysaccharide layer. This exposed the inner peptidoglycan layer, the coloured complexes are then washed away

Gram positive bacteria become dehydrated and traps the complexes in thicker peptidoglycan layer

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24
Q

What is used for decolourisation?

A

Alcohol/acetone

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25
Q

What is the outcome of counterstaining?

A

Gram negative become pink/reddish

Gram positive become purple

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26
Q

Summarise the structure of gram positive bacteria

A

2 layered wall

A thick peptidoglycan layer and a cytoplasmic membrane

Has lipoteichoic acid

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27
Q

Summarise the structure of gram negative bacteria

A

3 layers

An outer membrane

Think peptidoglycan layer inside the periplasmic space

Cytoplasmic membrane

Has Lipopolysaccharide

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28
Q

Describe peptidoglycan (PGN)

A

Polymer of sugars and amino acids

Forms a mesh-like layer outside plasma membrane

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29
Q

Describe lipoteichoic acid (LTA)

A

Complex of teichoic acid+lipids

Provides cell rigidity

Recognised by host immune cells

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30
Q

Describe lipopolysaccharide

A

Essential for function of outer membrane

Elicits potent immune and inflammatory host response

Produced endotoxins

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31
Q

What do outer membrane proteins do in the cell wall?

A

Not endotoxins but do contribute to virulence

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32
Q

Describe bacteria replication of genome

A

2 replication forks replicate DNA in a circular motion on either side of the ring

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33
Q

What is bacterial cell division called?

A

Binary fission

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34
Q

What is the four phases of bacterial growth?

A

Lag

Log/exponential

Stationary

Death

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35
Q

What happens in the lag phase?

A

Bacteria prepare for reproduction by synthesising DNA and enzymes

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36
Q

What does the lag phase represent?

A

The period of active growth ie size. not number

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37
Q

What happens in the log/exponential phase?

A

Cells divide at maximum rate

Uniform replication

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38
Q

What happens in the stationary phase?

A

The cessation of growth

Exhaustion of nutrients

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39
Q

What happens in the death phase?

A

The number of dying cells start to exceed the number of newly born cells

40
Q

What is bacterial recombination?

A

How bacteria share DNA

41
Q

What are three examples of bacterial conjugation?

A

Conjugation

Transformation

Transduction

42
Q

What is conjugation?

A

Genes are transferred through the pili tube

43
Q

What is transformation?

A

Taking up DNA from surrounding environment

44
Q

What is transduction?

A

Exchanging of bacterial DNA through bacteriophages

45
Q

What are the different areas of bacterial classification?

A

Gram staining

Cell shape

Atmospheric preference

Key enzymes

Fastidiousness

46
Q

What essentially is a virus?

A

A nucleic acid enclosed in a protein shell

47
Q

What are the difference viral structural components?

A

Nucleic acid

Capsid

Envelope

Spikes

48
Q

What are the different forms of nucleic acid that can be found in a virus?

A

Double or single stranded

Deoxyribonucleic or ribonucleic acid

49
Q

What is the capsid?

A

A protein coat/shell

50
Q

What forms capsid?

A

Composed of protein subunits called capsomeres

51
Q

What are capsomeres made from?

A

Aggregated protomeres

52
Q

What are the different shapes of capsid?

A

Rod-like

Polyhedral

Complex

53
Q

Describe the viral envelope

A

Amorphous structure surrounding some virus

Composed of lipid, protein and carbohydrate

54
Q

Example of a virus with an envelope?

A

Herpes

55
Q

Describe viral spikes

A

Glycoprotein projections arising from the envelope

56
Q

What is the function of viral spikes?

A

May have enzymatic, adsorption or haemagglutinin activity

57
Q

What is hemagglutination?

A

Clumping of RBC

58
Q

How does a virus replicate?

A

Uses host’s cellular machinery

59
Q

What are the 6 steps of viral replication?

A

Adsorption

Penetration

Replication

Assembly

Maturation

Release

60
Q

What happens in the adsorption step of viral replication?

A

Virus binds to the host cell

61
Q

What happens in the penetration step of viral replication?

A

Virus injects its genome into host cell via fusion, binding or ingestion

62
Q

What happens in the replication step of viral replication?

A

Capsid digested by proteolytic enzymes

Viral genome replicated using the host’s cellular machinery

63
Q

What happens in the assembly step of viral replication?

A

Viral components and enzymes are produced and begin to assemble

64
Q

What happens in the maturation step of viral replication?

A

Virus fully develops

65
Q

What happens in the release step of naked viruses in viral replication?

A

Viral enzymes break down bacterial cell wall

RNA viruses released

DNA viruses releases via autolyse or in inclusion bodies

66
Q

What happens in the release step of enveloped viruses in viral replication?

A

Viruses migrate to either the plasma membrane or nuclear membrane

Enveloped formed around nucleocapsids by “budding” of cell membrane

No inclusion bodies

67
Q

What are protozoa?

A

Single celled eukaryotes

68
Q

How do we classify protozoa?

A

Sporozoa

Flagellates

Amoeba

CIliates

69
Q

What are sporozoa?

A

Intracellular parasites

70
Q

What are flagellates?

A

Possess tail-like structures for motility

71
Q

What are amoeba?

A

Use temporary cell-body projections called pseudopods

72
Q

What are ciliates?

A

They move by beating multiple hair-like structures

73
Q

What protozoa leads to malaria?

A

Plasmodium falciparum

74
Q

What protozoa leads to giardiasis?

A

Giardia lamblia

75
Q

What protozoa leads to toxoplasmosis?

A

Toxoplasma gondii

76
Q

What protozoa leads to cryptosporidiosis?

A

Cryptosporidium parvum

77
Q

What are fungi?

A

Multinucleated eukaryotic organisms

78
Q

What is the wall of fungi made from?

A

Thick carbohydrate containing chitin and glucans

79
Q

How do fungi reproduce?

A

Reproduce asexually by budding and occasionally by binary fission

80
Q

What are fungal infection denoted by?

A

Mycoses

81
Q

What is candidiasis and what is it caused by?

A

Fungal infection

Candidiasis

82
Q

What is cryptococcosis and what is it caused by?

A

Fungal infection

Cryptococcus neoformans

83
Q

How do you treat cryptococcosis?

A

Amphotericin B

84
Q

What causes aspergillosis?

A

Aspergillus flavus

85
Q

How does aspergillus flavus cause aspergillosis?

A

Production of aflatoxins which then are inhaled

86
Q

What is ringworm caused by?

A

Tinea corporis

87
Q

Where does ringworm effect?

A

Scalp, skin, fingernails, toenails and feet

88
Q

What are helminths?

A

Parasitic worms

89
Q

What are the 3 main groups f helminths?

A

Cestoda- tapeworms

Trematoda- flukes

Nematoda- roundworms

90
Q

What are the four ways helminths can be transmitted?

A

Intermediate host

Faecal-oral route

Active skin penetration

Injection by blood-sucking insect

91
Q

What type of helminth is schistosomiasis caused by?

A

Fluke

92
Q

What helminths cause schistosomiasis?

A

Schistosoma haematobium

Schistosoma mansoni

Schistosoma japonica

93
Q

What type of helminth causes trichiuriasis?

A

Nematode

94
Q

What helminth causes trichiuriasis?

A

Trichuris trichiuria

95
Q

Example of a tapeworm

A

Taenia solium

MD2001 Week 4 (10 decks)

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