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Microbiology > Chapter 2: Cell structure and function > Flashcards

Chapter 2: Cell structure and function Flashcards

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Biology 101 flashcards
1
Q

Cell envelope

A

It is a series of layered structures surrounding cytoplasm and governing interactions with the environment.
It includes:
Cytoplasmic membrane
Cell Wall
Outer membrane
S-layers (capsules and slime layers)

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2
Q

Cytoplasmic membrane

A

Also called plasma membrane
Surrounds cytoplasm
its main function is selective permeabilty so nutrients enter and wastes leave and membrane proetins facillitate these reactions and functions in energy metabolism

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3
Q

Plasm membrane structure

A

8-10nm wide
It is a phospholipid bilayer containing embedded proteins
It contains both hydrophobic fatty acid tails and hydrophilic glycerol and phosphate and other functional groups
The fatty acids associate inwards to form hyrdrophobic environment and the hydrophilic head groups remain exposed to external environment and cytoplasm

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4
Q

membrane proteins

A

Embedded proteins: Integral membrane proteins
Transmembrane proteins: extend completely across membrane
Peripheral membrane proteins; Loosely attached

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5
Q

Domains

A

Bacteria
Archae
Eukarya

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6
Q

Archael cytoplasmic membranes

A

-Ether linkages
-Archael lipids have isoprenes instead of fatty acids
-Major lipids are phosphoglycerol diethers with phytanyl C20 side chains and diphosphoglycerol tetra
-Many different isoprenoid chains including ring structures

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7
Q

Cytoplasmic membrane function

A

-Permeability barrier
* Polar and charged molecules must be transported
* Transport proteins accumulate solutes against concentration gradient
-Protein anchor
*Holds proteins in place
_energy conservation and consumption
* Generation of proton motive force

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8
Q

Eukaryotic plasma membrane

A

-Eu and Bac have ester linkages
-Contain Carbohydrates that function as attachment and receptor sites
-Contains Glycoproteins
-Contains sterols
*HUmans contain cholestral while fungal cells contain ergosterol

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9
Q

NB antifungal target

A

Ergosterol in membrane

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10
Q

Active transport mechanisms

A

-Simple transport
-Group translocation
-ABC system

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11
Q

Simple transport

A

-Driven by proton motor force
-Either symport: solute and H+ cotransported in one direction
-Or antiport: Solute and H+ transported in different directions

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12
Q

Group translocation

A

-Substance transport is chemically modified
-Energy-rich organic compound (not proton motive force) drives transport
-Best studied

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13
Q

E.Translocation

A

Phosphotransferase system in E.coli
-glucose, fructose and mannose
-5 proteins required
-energy from phosphoenolpyruvate

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14
Q

ABC transporter system

A

ABC= ATP binding cassette
-200 different systems for organic and inorgnic
-Substrate binding proteins outside of cell have high substrate affinity
-ATP drives uptake
-Binding protein binds to target and brngs it to transporter. Transporter breaks down ATP to transport target across

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15
Q

What type of organisms prefer ABC transporters

A

EXtremophiles as they are under stress with limited resources and ABC allow them to find specific substances in small concentrations

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16
Q

Cell Wall

A

-Needs to withstand osmotic/turgor pressure to prevent cell lysis
-Maintains cell shape and rigidity
-Bacteria seperated into two groups based off gram stain

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17
Q

Gram positive

A

envelope contains cytoplasmic membrane and thick cell wall with many layers of peptidoglycan
stains purple

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18
Q

Gram negative

A

Envelope consistes of membrane, thin cell wall with very little peptidoglycan, outermembrane and periplasm
stains pink

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19
Q

Bacterial cell wall component

A

It contains glycan tetrapeptide which is made up of:
-Sugar backbone (alternating modiefed glucose made of NAG and NAM joined by B1-4 linkages
-The linkage is what is targeted
-Short peptides are joined to NAM like L-alanine, D-alanine, D-glutamic acid, L-lysine or DAP

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20
Q

NAG

A

N-acetylglucosamine

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21
Q

NAM

A

N-acetylmuramic acid

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22
Q

DAP

A

diaminoplimelic acid

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23
Q

Go over diagram of gram positive

A
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24
Q

DIagram of Gram negative

A
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25
Q

Acid fast cell walls

A

Cells contain a high percentage of mycolic acid
-Hydrophobic waxy lipid
Forms a layer outside of the tin peptidoglycan layer
-Causes cells to stick together
-Is detected by acid fast stains

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26
Q

Archael cell walls

A

-Lack peptidoglycan and outer membrane
-Most lack polusaccharide wall and instead of S-layer (protein shell)

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27
Q

Archael cell wall makeup

A

-pseudomurein cell wall
-similar to peptidoglycan
-Alternating NAg and NAT
-B1-3 glycosidic bonds instead of B1-4
-Amino acids all L-stereoisomer

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28
Q

NAT

A

N-acetyltalosaminuronic acid

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29
Q

Arachael sensitivity to lysosmes

A

Enzymes are specific to B1-4 bonds instead of B1-3

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30
Q

Eu cell walls

A

Plants contain cellulose
Fungi contain chitin which is a polymer of NAG units and is an important antifungal drug target
Yeast cell walls contain glucan and mannan

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31
Q

Outer membrane structure of gram negative

A

second bilayer external to cell wall
-Outer membrane contains polysaccharides covalently bound to lipids: lipopolysaccharide layer (LPS)
-Facilitates surface recognition, important virulence factors and add strength
-Contains porins

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32
Q

LPS

A

lipopolysaccharide layer
-Contains core polysaccharide and O-polysaccharide
-Lipid bond sto divalent cations (Mg2+) and adds strength
-Lipid A portion
-LPS replaces most of phospholipids in outer half of membrane

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33
Q

Braun lipoprotein

A

ANchors outer membrane to peptidoglycan

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34
Q

Endotoxin

A

Lipid A, toxic component of LPS when cell dies
responsible for symptoms associated with infection

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35
Q

core polysaccharide

A

Attached to lipid A and provides structural stability

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36
Q

O polysaccharide

A

Functions as antigen and is useful for distinguishing between different strains
antibodis bind here

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37
Q

S-layer

A

paracrystalline structure consisting of protein or glycoprotein
-Always outermost layer
-functions: strenght, protection from lysis, conferring shape, creating periplasmic-like space, facilitting cell surface interactions, promoting adhesion, protecting cell from host defences

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38
Q

Mycoplasms

A

tough cell membrane in Bac without cell wall

39
Q

Thermoplasm

A

Tough cell membrane in Archae that lack cell walls

40
Q

Capsule and slime layer component

A

sticky polysaccaride coat outside cell envelope

41
Q

Capsule

A

If tightly attached, tight matrix; visible if treated with INdia ink

42
Q

Slime layer

A

Loosely attached, eaily deformed and is easier to wash off than capsuleC

43
Q

Capsule and Slime functions

A

Assist in attachment to surfaces
Roles in development and maintanence of biofilms
Contribute to infectivity ( capsule pieces kill macrophages)( prevents antibiotic from reaching target)
Prevent dehydration/desiccation

44
Q

Surface structures

A

Hair like appendages shorter than flagella
made of pillin
include fimbriae and Pili

45
Q

Fimbria

A

Can occur all over the cell
Numbers in 100s
involved in biofilm formation and colonisation

46
Q

Pilus

A

Longer than fimbriae
only few per cell
Functions:
-Motility by twitching and glidng
-DNA transfer (conjugation)

47
Q

Hamus/Hami

A

Archael grappling hooks that assist in surface attachment and forming biofilms
-structurally resemble type IV pili except for barbed termini, which attaches cells to surfaces or each other

48
Q

Cell inclusions

A

Function as energy reserves, carbon or phosphorus reservoirs and or have special fucntions
-enclosed by thin protein membrane
-reduce osmotic stress

49
Q

Carbon storgae polmers

A

-synthesised when carbon in excess
-broken down as carbon or energy sources if needed
-glycogen is a glucose polymer

50
Q

Phosphate granules

A

Inorganic phosphate
elemental sulfur accumulates in periplasmic granules and oxidised to sulfate (SO4)

51
Q

Sulfur granules not found in Gram positive

A

Thick layer prevents periplasmic layer from expanding as much which reduces storage space

52
Q

Magnetosomes

A

Allow bacteria to orient within magnetic field
-Biomineralised magnetic iron oxides
-Allow cell to undergo magnetotaxis: migration along magnetic field lines

53
Q

Gas vesicles

A

Conical-shaped, gas filled structures made of two proteins

54
Q

Endospores

A

Dormant, tough and non-reproductive structure produced by certain bacteria (usually gram positive)
-Formation triggered by lack of nutrients
-Able to survive for millions of years through hasrh conditions and structures are not metabolically active

55
Q

exosporium

A

Outer layer
-interacts with environment or host organism and may contain spore antigens which trigger an immune response

56
Q

Spore coat

A

Resistant to many toxic molecules and may also contain enzymes involved in germination

57
Q

Cortex

A

Beneath the spore coat and consists of peptidoglycan and makes the endospore resistant to temperature

58
Q

core wall

A

provides endospore resistance to UV light and harsh chemicals

59
Q

Core

A

Contains spore chromosomal DNA
-Encased in chromatin -like proteins known as SASPs
-SASPs protect spore DNA from UV radiation and heat
-DPA further stabilises protein and DNA
-Also contains normal cell structure such as ribisomes and other enzymes

60
Q

SASP

A

small acid-soluble spore proteins

61
Q

DPA

A

Dipicolinic acid

62
Q

Endosprulation

A

Insert

63
Q

Endospore germination

A

INsert

64
Q

how to kill endospores

A

-destroyed by burning or autoclaving (takes several hours)
-Prolonged exposure to ionising radiation
-A 10% sodium hypochlorite solution where contact time exceeds 10 minutes
-Hospitals use ethylene oxide which is a low-temp sterilant

65
Q

Flagella

A

-assists in swimming in Bac and Archae
-Long thin appendages (15-20nm wide) anchored in cell
-Different arrangements
-Increase or decrease rotational speed relative to strenght of proton motive force

66
Q

Polar/monotrichous

A

single flagellum at 1 pole

67
Q

Lophotrichous

A

Tuft of flagella at one pole

68
Q

Amphitrichous

A

Flagella at both poles

69
Q

Peritrichous

A

Flagella all over

70
Q

Amphilophotrichous

A

Tuft of flagella at both ends

71
Q

Flagella structure

A

Filament composed of flagelin protein
-hook
-basal body
* G-Neg have 2 sets of rings (one to cell wall and one to plasma membrane)
*G-Pos only have inner set of rings

72
Q

Flagella synthesis

A

Several genes
MS ring made first
Anchoring proteins, hook, cap are made next
Filament forms with flagellin exported through export apparatus

73
Q

Movement with bundeled flagella

A
74
Q

MOvement with single flagella

A
75
Q

Archaella

A

proteins unrelated to flagella, more closely related to type IV pili
-smaller than bacterial flagella
-Move by rotation driven by ATP hydrolysis (move slower)

76
Q

Twitching motility

A

Requires Type IV pili
extend from one cell pole, attach to surface, retract to pull cell forward
-Energy from ATP hydrolysis

77
Q

Gliding motility

A

smooth, continuous motion along long axis without external structures
-Only bacteria
-helical intracellular protein track, gliding motors and adhesion proteins

78
Q

Taxis

A

Directed movement in response to chemicl or physical stimuli
enhances access to resources and allows avoidance of death

79
Q

Chemotaxis

A

Chemicals

80
Q

Phototaxis

A

Light

81
Q

Run and tumble behaviour

A

Run: smooth motin, flagellar motion rotates counterclockwise
Tumble: stops and jiggles because flagellar motor rotates clockwise, flagellar bundle comes apart
-after tumble another run beings in a random direction

82
Q

Biased random walk

A

Bacterial respond to temporal and not spatial differnce in chem concentration
increaed chem gradient results in longer lenght of run

83
Q

Osmotaxis

A

ionic strength

84
Q

Hydrotaxis

A

water

85
Q

Aerotaxis

A

Oxygen

86
Q

Magnetotaxis

A

Magnetic current
It is used to wim toward or away from O2

87
Q

Scotophobotaxis

A

Response to absence of light
enetering darkness causes cells to tumble and head back to light

88
Q

Mitochondria

A

respiration and oxidative phosphorylation for aerobic Eu
number varies
surrounded by 2 membranes
-Cristae:folded internal membranes
-contain enzymes needed for respiration and ATP production
-Matrix: inermost area and contains citric acid enzymes

89
Q

Chloroplasts

A

Contains chlorophyll
site of photsynthesis
double membrane
innermemrane surrounds stroma and contains large amounts of RuBisCO for Calvin cycle
Thylakoids are flattened membrane discs containing chlorophyll and ATP synthetic components and form proton motive force

90
Q

Cytoskeleton

A

Microtubules
-Hollow tube that have 25nm diamters and are composed of alpha and beta tubulin
-Maintain cell shape, motility, move chromosomes and organelles
Microfilaments
-7nm in diamter and are polymers of actin protein
-Maintain and change cell shape; involved in amoeboid motility and cell division
Intermediate filaments
-8-12nm in diameter; fibrous keratin proteins
-Maintain cell shape and position organelles

91
Q

Endoplasmic reticulum

A

Rough contains ribisomes while smooth does not
Smooth participates in synthesis of lipis and carb metabolism
Rough produces glycoproteins and new membrane material

92
Q

Golgi Complex

A

Stacks of membrane-bound sacs modifying ER products

93
Q

Lysosmes

A

Membrane enclosed compartments containing digestive enzymes and recycling cell components

94
Q

Flagella and Cili

A

Cilia are shorter than Flagella and beat in synchrony
Eu flagella are long and propel through whiplike motion
protein called dynein found in them

Microbiology (6 decks)

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