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Medical Microbiology > Lecture 2 > Flashcards

Lecture 2 Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

What are the 7 differences between prokaryotic and eukaryotic cells?

A

Nucleoid/nucleus ; 1/46 chromosomes ; membrane-bound organelles ; ribosome sizes (16S/18S) ; sexual reproduction (prok = conjugation) ; meiosis/mitosis/binary fission ; cell size

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2
Q

Define “bacteria”

A

small unicellular microorganisms that live freely (not part of a higher structure like organ/tissue)

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3
Q

What are the 3 problems with living freely?

A

nutrition (efficiency and need to adapt if lack) ; occupation (adherence and needing to form biofilms) ; resistance to damaging agents (such as antibiotics)

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4
Q

Why is surface area important for a cell?

A

for transport of nutrients from outside to inside of the cell or release of waste from inside to outside

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5
Q

What were to happen if we had the same surface area as bacteria?

A

increase nutrient consumption, increase waste excretion, and shorter generation time

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6
Q

What is the benefit/consequence of having a smaller surface area when it comes to metabolic rate?

A

increase in metabolic rate = complete processes faster

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7
Q

What is the generation time for E.coli?

A

20 minutes

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8
Q

What is the benefit of the ability of bacteria to grow fast?

A

faster infection time, can easily change and adapt faster, can pass the adaptation to next generation

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9
Q

What is a consequence to us due to the ability of bacteria to grow fast?

A

poses a challenge against antibiotics

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10
Q

What components would you typically find in a bacteria’s cytoplasm?

A

nucleoid chromosome, plasmids, ribosomes, inclusion bodies

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11
Q

Describe the characteristics of a bacterial chromosome?

A

no-membrane, double-stranded, circular, bigger than plasmids

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12
Q

How many copies of chromosomes do bacterial cells have?

A

one per cell

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13
Q

How many copies of plasmids do bacterial cells have?

A

as many as one or more per cell

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14
Q

What are plasmids?

A

Extrachromosomal genetic material that bacterial cells can survive without

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15
Q

Why are plasmids important?

A

helps with adaptation and survival, includes pathogenetic and antibiotic-resistant genes

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16
Q

What are inclusion bodies?

A

aggregates of a particular compound (ie: protein A)

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17
Q

Where are inclusion bodies found?

A

cytoplasm

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18
Q

Function of inclusion bodies?

A

used for storage

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19
Q

Where can you also find inclusion bodies in gram- bacteria?

A

periplasm

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20
Q

What is a cell envelope?

A

describes everything that is outside of the cytoplasmic membrane

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21
Q

What are the functions of the cell envelope?

A

protect cytoplasm, facilitates adherence (ie: adhesin on cell wall) and colonization (chains or grape clusters)

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22
Q

What defines the outer-membrane?

A

lipopolysaccharide

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23
Q

What are the components of gram+ cell envelope?

A

cytoplasmic membrane > THICK peptidoglycan > Teichoic acid and LTA (lipoteichoic acid)

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24
Q

What is murein?

A

peptidoglycan

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25
Q

What is Teichoic acid?

A

acidic polymers usually found on gram+ cell walls

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26
Q

What is lipoteichoic acid?

A

teichoic acid with fatty acid chain on N terminus

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27
Q

Function of lipoteichoic acid

A

stabilizes cell envelope

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28
Q

What are the components of gram- cell envelope?

A

cytoplasmic membrane > periplasm > THIN peptidoglycan > outer-membrane

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29
Q

What are the 2 main types of membrane proteins?

A

integral and peripheral

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30
Q

What are the main functions of the cytoplasmic membrane?

A

permeability barrier, protein anchor, energy conservation

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31
Q

What is another form of energy that bacterial cells use other than ATP?

A

in the form called “proton-motive force”

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32
Q

What is “proton-motive force”?

A

bacterial cytoplasmic membrane functions like a battery = transfer of protons across membrane = generates energy used for process such as transport

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33
Q

Where would a bacterial cell use the “proton-motive force” and why?

A

cell envelope because ATP is only present in cytoplasm, not cell envelope

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34
Q

What is the cell wall made out of? (macromolecule)

A

carbohydrates

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35
Q

What type of bond is used to link the sugar molecules?

A

ß(1,4) glycosidic bond

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36
Q

What are the 2 sugars that compose the peptidoglycan?

A

N-acetyl Murmuric acid (murein) and N-acetyl Glucosamine (glucose)

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37
Q

What links the sugar chains to each other and why?

A

amino acids for stability

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38
Q

What isoform do the amino acids take within the peptidoglycan cell wall?

A

D-isoform

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39
Q

What is a glycine interbridge?

A

5 glycine interbridge in thick peptidoglycan (gram+ ONLY)

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40
Q

How is the cell wall differentiated between species?

A

sequence of amino acids that hold sugar chains together

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41
Q

Which bacterial species will have the glycine interbridge?

A

gram+

42
Q

Apart from the 20 amino acids, where can rare/unique amino acids be found? How can this benefit the bacteria?

A

within cell walls of bacteria, benefits in antimicrobial resistance

43
Q

Where are the cell-wall building block synthesized in bacteria?

A

in the cytoplasm

44
Q

What is UDP?

A

protein that helps transport the sugar chain across cytoplasmic membrane into exterior of cell or periplasm

45
Q

What is the first antibiotic discovered?

A

penicillin

46
Q

What does penicillin target? How does this affect the bacteria?

A

inhibits further cell wall synthesis and begins to break down exisiting cell wall ==> eventually will lyse bacteria

47
Q

What is a good thing to look at when choosing an antibiotic to use?

A

choose what will minimize its effects to only bacterial species, not eukaryotic cells

48
Q

What is the downside to using an antibiotic?

A

targets normal flora as well

49
Q

Functions of periplasm?

A

transport across cell envelope and helps in protein folding

50
Q

What are the proteins contained in periplasm?

A

hydolytic enzymes, binding proteins, chemoreceptors, and molecular chaperones

51
Q

What is the purpose of molecular chaperones in the periplasm?

A

for proteins that are meant to be excreted/secreted = need to go through cell envelope and fold in the periplasm –> transport to outer membrane

52
Q

What differentiates outer-membrane and inner-membrane?

A

outer-membrane has lipopolysaccharide on the outer leaflet of outer-membrane

53
Q

What are trimeric porins?

A

integral membrane protein found on gram– that act as a channel for certain molecules to pass through outer-membrane (dictates size of what can pass through)

54
Q

What are unique characteristics of the outer-membrane?

A

lipopolysaccharide and trimeric porins

55
Q

What binds to the inner-leaflet of the outer-membrane and what is it’s function?

A

lipoprotein binds to peptidoglycan and stablizes cell envelope

56
Q

What are surface appendages on bacterial cells?

A

structures located on the surface of bacterial cells

57
Q

Which type of bacterial do surface appendages apply to?

A

all 4 types of bacteria

58
Q

What are the 4 types of surface appendages?

A

flagella, pili, capsule, S-layer

59
Q

What is the function of flagella?

A

motility

60
Q

What is a petrichous arrangement of flagella and which family does it characterize?

A

flagella coming from all over the bacterium, family I

61
Q

What is a polar arrangement of flagella and which family does it characterize?

A

more than 1 flagella all bunched up on one side of the bacterium, family II

62
Q

Which family of flagella will we be dealing most with in this class?

A

Family I

63
Q

What is chemotaxis?

A

movement towards substances that attract or move away from those that repel

64
Q

How will petrichous flagella move?

A

bind together as one

65
Q

Which way does the bacterium move forward with flagella (counter-clockwise or clockwise)

A

counter-clockwise

66
Q

What species of bacteria is flagella best mostly studied from and what type of bacteria are they?

A

E.coli and Salmonella, gram–

67
Q

What are the 3 main parts of the flagellum structure?

A

basal body, hook, filament

68
Q

What are the 4 rings of the basal body?

A

C (Cytoplasmic), MS (motor surface), P (Peptidoglycan), L (lipopolysaccharide)

69
Q

What is the protein that makes up the filament of the flagella?

A

flagellin

70
Q

About how many proteins compose the flagella?

A

40 different proteins for assembly

71
Q

What types of bacteria can have a flagella?

A

All 4 types but we focus on gram– for the most part

72
Q

In what order does assembly of flagella start?

A

basal body > hook > filament

73
Q

Does a bacterium always have a flagella?

A

no, only assembles when it needs it (ie: need to move)

74
Q

What is a pili also called?

A

fimbriae

75
Q

What is a pili?

A

shorter and thinner appendage than flagella and can have 2x as more than flagella on the surface

76
Q

What is the main function of a pili and what is it also used for?

A

adherence and conjugation

77
Q

What is the most-studied pili and which species was it found in?

A

P-pili in uro-pathogenic (UTI-causing) E.coli

78
Q

Where does the pili get assembled?

A

on the surface of outer membrane

79
Q

How many different proteins does the pili get assembled with?

A

10

80
Q

Which proteins play a key role in the P-pilus assembly?

A

C and D

81
Q

What role in the P-pilus assembly does the “C” protein do?

A

outer-membrane usher = kind of a porin that helps transport protein across and assemble on top of it

82
Q

What role in the P-pilus assembly does the “D” protein do?

A

periplasmic chaperone for assisting protein folding; brings proteins to C protein

83
Q

What is a variation of the P-pilus?

A

Type I pilus

84
Q

What is a capsule

A

polysaccharide encasing the bacterium

85
Q

What is the function of a capsule?

A

protection and sometimes attachment

86
Q

Do all bacterium have capsules?

A

not all and they don’t always have it

87
Q

What is an S-layer?

A

2-dimensional array of protein on bacterium surface

88
Q

What is the function of an S-layer?

A

additional protection to the cell

89
Q

Do all bacterial species have the same S-layer?

A

No, arrangement of S-layer lattices are species dependent

90
Q

What is an endopsore?

A

what the bacteria develops into during mid-binary fission when it is living in extreme harsh conditions

91
Q

What is the function of an endospore?

A

for the bacterium to survive

92
Q

Which type of bacteria can develop into endospores? What species?

A

gram+ bacillus and clostridium

93
Q

What is a vegetative cell?

A

a typical bacterial cell without an endospore

94
Q

How does endospore formation begin?

A

duplicates chromosome, acts as if cell is getting ready to divide but there is no septum

95
Q

What kind of cell division does endospore formation take place? What happens after this division?

A

asymmetrical division; smaller piece will become a spore and the rest will lyse

96
Q

What chemical compound is specifically found in spores?

A

dipicolinic acid

97
Q

What is a function of dipicolinic acid?

A

helps spore become resistant to harsh environment

98
Q

During endospore formation, which layer will the spore be present?

A

cytoplasm

99
Q

Does an endospore have any metabolic activity? Why or why not?

A

No because the endospore is at an “inactive” state since it’s only goal is to survive and waits for the harsh environment to pass until it becoems a vegetative cell again

100
Q

What mechanism/pathway plays an important role in pathogenesis?

A

protein secretion (virulence factors)

Medical Microbiology (20 decks)

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