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MICRB 265 > Week 3 > Flashcards

Week 3 Flashcards

1
Q

bacterial cell envelope is anything ______

A

from the plasma membrane out

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2
Q

parts of gram + bacteria cell envelope (inner to out)

A

-periplasm (gel-like cytoplasm outside pm)
-thick peptidoglycan layer

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3
Q

parts of gram - bacteria cell envelope (inner to out)

A

-periplasm (gel-like cytoplasm outside pm)
-thin peptidoglycan layer
-periplasm (gel-like cytoplasm outside pm)
-outer membrane (only in gram -)

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4
Q

PM are mostly ______

A

phospholipids and carbohydrates with proteins imbedded within

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5
Q

functions of cytoplasmic membrane

A

1) permeability barrier: prevents leakage, transport of nutrients in and wastes out
2) protein anchor: proteins participate in transport etc.
3) energy conservation: charge differential across membrane

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6
Q

parts of PM

A

fatty acid tail chains –> glycerol –> phosphate head group –> sidechain

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7
Q

glycerol is connected to lipid tails in PM by ____ in bacteria and eurkarya but not archaea (____)

A

-ester linkage
-ether linkage

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8
Q

saturated fatty acids are ____
unsaturated fatty acids are _____

A

-straight, inflexible
-kinky, mobile

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9
Q

types of phospholipids most common in e-coli

A

-Phosphatidylethanolamine
-Phosphatidylserine

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10
Q

phospholipid + side chain
a) Phosphatidic acid
b) Phosphatidylethanolamine
c) Phosphatidylserine
d) Phosphatidylcholine
e) Phosphatidylglycerol
f) Cardiolipin

A

a) X=H
b) X=CH2CH2NH3
c) X=CH2CH2(NH3)COOH
d) X=CH2CH2N(CH3)3
e) X=CH2CH(OH)CH2OH
f) X=Phosphatidylglycerol

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11
Q

lipid acyl chains affects _____

A

membrane fluidity

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12
Q

PM with only saturated lipids is needed for _____

A

bacteria that lives in high temp

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13
Q

PM with mixed saturated/unsaturated lipids is needed for _____

A

bacteria that lives in low temp

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14
Q

____ , an activated carrier molecule, is also part of PM and consists of _____.

A

-undecaprenyl pyrophosphate
-55C in isoprene units and 2 PO4

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15
Q

integral membrane proteins are ____

A

imbedded in the membrane

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16
Q

types of integral membrane proteins

A

1) monotopic alpha helix - cross PM once
2) polytopic alpha helices - cross PM more than once
3) polytopic beta barrel - cross PM more than once

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17
Q

peripheral membrane proteins are ______

A

associated with membrane on either side but not imbedded

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18
Q

types of peripheral membrane proteins

A

1) alpha helix (part of protein associates with membrane)
2) loops associated with membrane
3) acylated (fatty acid attached imbedded in membrane)
4) ionic (charged interactions with hydrophilic head groups)

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19
Q

diffusion (def., energy requirement, permitted/not permitted to pass)

A
  • Free movement of molecules along a concentration gradient
  • Does not require energy (passive)
  • Permitted: Small hydrophobic molecules, Water, O2,CO2
  • Not permitted: Charged molecules (ions), large hydrophilic molecules (sugars, NA. proteins, etc.)
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20
Q

osmosis (def.)

A

Movement of water along a concentration gradient

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21
Q

osmosis can do what?

A

Can exert a physical force on the membrane

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22
Q

hypertonic solution (def.) + effect on cell

A

-[H2O] outside cell < [H2O] inside cell
-H2O leaves cell & cell dehydrates

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23
Q

isotonic solution (def.) + effect on cell

A

-[H2O] outside cell = [H2O] inside cell
-no net movement of water

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24
Q

isotonic solution of bacteria is not ____

A

saline like for animal cells

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25
hypotonic solution (def.) + effect on cell
-[H2O] outside cell > [H2O] inside cell -animal: H2O enters cell & cell burst no net movement of water -bacteria: peptidoglycan and S-layers prevent cell from bursting
26
facilitated diffusion (def., energy requirement, permitted/not permitted to pass)
* Movement of molecules along a concentration gradient - requires a protein carrier that is selective for its substarte (size-dependent) * Does not require energy (passive) * Ions, sugars, amino acids can pass
27
In facilitated diffusion, movement rate is determined by ____
the number of transporters & transporter affinity for solute & a bit of [solute]
28
in simple diffusion, movement rate is ____
directly proportional to [solute] - linear
29
types of transporters
-uniport -symport -antiport
30
uniport (def.)
protein transporter that moves one molecule across membrane, usually facilitated diffusion
31
symport (def.)
protein transporter that moves two molecules across membrane in same direction (can use energy from proton motive force)
32
antiport (def.)
protein transporter that moves two molecules across membrane in opposite direction (can use energy from proton motive force)
33
proton motive force (PMF) (def.)
* Higher concentration of protons outside the cell * Protons want to go inside cell along concentration gradient * Proton movement contains energy
34
PMF can be used to transport _______
molecules against a concentration gradient
35
How Glucose transport work?
- glucose enter cell via facilitated diffusion - when glucose enters cell, it is phosphorylated immediately upon entering cell - glucose-6-phosphate cannot enter transporter - glucose gradient still maintained
36
active transport (def., energy requirement, permitted/not permitted to pass)
* Movement of molecules against a concentration gradient - requires a protein carrier * Requires energy, usually in the form of ATP (active) * Transporters are selective for particular substrates * Movement rate is limited by the number of transporters * Used to pump nutrients into the cells and harmful substances out of the cell
37
ABC (______) transporters description
- ATP binding casette - 4 parts (4 separate proteins or 1 protein with 4 domains)
38
parts of ABC transporters
-2 transmembrane domains -2 nucleotide binding domain in the cytoplasm
39
how ABC transporters work?
-substrate binds to binding protein which helps facilitate interaction with ABC transporter -ATP bound transporter is in outward facing position + substrate binds to transporter -ATP hydrolysis opens transporter to cytoplasm and substrate enters cytoplasm
40
peptidoglycan general structure
-polysaccharide backbone (made from disaccharide monomer) linked by peptides = glycan tetra-peptide
41
disaccharide monomer of peptidoglycan
-N-acetylmuramic acid (MurNAc) & N-acetylglucosamine (GlcNAc) linked through B (1,4) linkages
42
B (1,4) linkages of peptidoglycan are _____
the bonds broken by lysozyme when degrading peptidoglycan
43
tetrapeptide of peptidoglycan is found in ______
mature peptidopglycan (immature form has extra a.a that are cleaved off)
44
tetrapeptide of peptidoglycan is attached to _____
-N-acetylmuramic acid (MurNAc) via COOH group
45
tetrapeptide of peptidoglycan in e-coli
-l-alanine (connected to MurNAc) -d-glutamic acid -diaminopimelic acid (forms peptide cross-links to neighbouring d-alanine) -d-alanine
46
some gram + bacteria like staphylococcus aureus have _____ in peptidoglycan (gram - bacteria have direct links)
peptide interbridges (ex. glycine) between tetrapeptides (thick peptidoglycan)
47
glycosidic bonds of peptidoglycan are ___ while peptide bonds are ____
-within one layer (strength around cell) -between layers (strength along axis of cell)
48
diaminopimelic acid (DAP) is the _____
acid version of lysine (EXTRA NH2)
49
* In Gram-negative bacteria the peptidoglycan layer is ____ and is located ______ * In Gram-positive bacteria, the peptidoglycan layer is _____ and is located _____
-2-7 nm thick (1-3 layers) -between the inner and outer membranes -between 20 and 35 nm thick (~15 layers) -outside the plasma membrane
50
Particles of _____ can freely traverse the peptidoglycan layer, while others need a protein channel/carrier + examples
2 nm or less (Na+, H2O, monosacc., disacc., ATP, lysozyme sometimes)
51
Teichoic acids are what?
-sugar-alcohol phosphate thats form covalent bonds with peptidoglycan
52
Lipoteichoic acids are _____
Teichoic acids attached to lipids (attach cell wall to cell membrane)
53
Teichoic acid monomer structure
-ribitol (reduced form of ribose with OH groups- linear) -3 peptides attached to OH groups of ribitiol and 2 phosphate attached to ends of ribitol
54
gram negative outer membrane descr.
* Asymmetric * Inner leaflet = phospholipids * Outer leaflet = lipopolysaccharide (LPS)
55
parts of LPS (outer to inner)
-O-specific polysaccharide (repeats, interacts with environment/immune system, strain dependent) -core polysaccharide (more variable, KDO + Hep sugars +PO4) -Lipid A (anchored in membrane with acyl chains & GlcN sugar + phosphate)_
56
lipid A core is made in ____ while O -antigen is _____
-one piece -made in another process which allows for diversity of O.antigen
57
O antigen biosynthesis
O-antigen is synthesized in undecaprenyl pyrophosphate in cytoplasm and it's flipped into periplasm by Wzx (ATP-independent) and repeating units are synthesized by Wzy & Wzz
58
LPS core biosynthesis
core synthesized in cytoplasm then MsbA (ABC transporter) flips lipid A CORE in periplasm
59
LPS core and O-antigen ligation & export
-WaaL helps lIgate lipid core to O-antigen with energy from PP of O-antigen/undecaprenyl pyrosphospate -ABC transporter (Lpt proteins) experience conformational change to LptA (bridge from cytoplasmic membrane to outer membrane) to move LPS to outer membrane
60
endotoxin of lipopolysacchride is _____
lipid A portion
61
lipopolysaccharide function
* Contributes to negative charge on cell surface * Helps stabilize outer membrane structure * May contribute to attachment to surfaces and biofilm formation * Creates a permeability barrier * Protects from host defenses (O antigen)
62
porins are ______
* Mostly β-barrel trimeric proteins that allow molecules to passively cross membranes found in gram-negative outer membrane
63
porins function
*Contribute to making outer membrane more permeable than cytoplasmic membrane
64
Types of Secretion systems in gram negative bacteria
1) Type I: secrete proteins outside cell 2) Type II: secrete proteins outside cell but proteins from Sec/Tat 3) Type V: like Type II but protein is unfolded first 4) Type III: secrete protein in another bacterial cell 5) Type IV: like Type III but DNA instead (like pilus) 6) Type VI: like type III but has sheath/needle that contracts to inject cell
65
S layers are what?
* Crystalline later of (glyco)proteins * Uncommon in bacteria * Self-assemble into 2-dimensional sheets attached to LPS or peptidoglycan * Protection against bacteriophage, low pH, lytic enzymes
66
There are multiple configurations of _____
cell envelope
67
capsules are ____
really long polysacch. that help with protection and help with attachment (slime layer)
68
glycocalyx (def.)
all the polysaccharides outside cell membrane
69
glycocalyx examples
* Lipopolysaccharide/teichoic acid/S-layer glycans * Capsule * Alginate * Poly-N-acetylglucosamine * Enterobacterial common antigen * Cellulose
70
pili are what?
-Thin (2–10 nm in diameter) filamentous structures * Made of protein * Extend from the surface of a cell * Retractable
71
pili are found in _____
* all Gram-negative bacteria and many Gram-positive bacteria
72
pili or fimbrae functions
* Conjugation (transfer of genetic material) * Electrically conductive pili * Type IV pili (type of secretion system)
73
Type IVa pilus structure
-pilus made for pilin subunit -structure that stabilizes pilus in peptidoglycan and anchor in inner membrane
74
motility on solid surfaces
a) twitching: uses pilus that extends, attach to surface and then retracts causing forward movement b) gliding: uses helical intracellular protein track with extracellular adhesion proteins & PMP --> helical movement of adhesion portions causes forward motion and rotation of cell
75
motility on semisolid surfaces
-swarming (mediated by flagella, coordinated movement that leads to dendritic patterns)
76
types of bacterial flagella
1) peritrichous (multiple all over) 2) polar (1 at a pole of cell) 3) lophotrichous (multiple @ one pole)
77
bacterial flagella grows ___
at the ends as flagellin is transported through hollow tube
78
flagella uses ____ to propel movement as____
-PMP -protons enters cells through stator
79
parts of flagella
-hollow filament made of flagellin monomer -hook (flexible) -motor (MS/C ring) -stator (anchors flagella in peptido. + cytoplasm)
80
flagella synthesis
-MS/C ring + motor proteins -P ring -L-ring -early hook -late hook + cap - filament synthesis + cap on top
81
e-coli flagella
peritrichous
82
swimming motility of peritrichous flagella
CCW rotation - cell runs (fwd motion)= bundled flagella CW rotation - cell tumbles = flagella spread apart
83
swimming motility of polar/lophotrichous flagella
a) reversible flagella --> CCW rotation - cell runs (fwd motion) CW rotation - cell reverses b) unidirectional flagella CW rotation - cell runs (fwd motion) rotation stops + random reorientation CW rotation - cell runs
84
chemotaxis
movement of bacteria in a chemical gradient (generally towards higher concentration of nutrients) - net movement towards attractant (runs are longer)- random tumbles still occurs sometimes away from attractant
85
phototaxis
movement of bacteria towards light/ maybe specific wavelength
86
aerotaxis
movement of bacteria according to oxygen conc.
87
magnetotaxis (gram negative)
movement of bacteria in magnetic field

MICRB 265 (12 decks)

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