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MCB 2610 > EXAM 3: Chapter 2- Part 2 > Flashcards

EXAM 3: Chapter 2- Part 2 Flashcards

1
Q

passive diffusion

A

Not energy dependent
Molecules move from higher concentration to lower
rate of diffusion depends on concentration gradient
Can be reversible depending on gradient

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2
Q

Examples of molecules that move across membrane by passive diffusion

A

H2O
O2
CO2

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3
Q

Facilitated diffusion

A

uses carrier proteins
used for larger and charges molecules
is reversible
gradient can be maintained by transforming the nutrient
happens primarily in Eukaryotes

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4
Q

How is facilitated SIMILAR to passive

A

movement is not energy dependent
direction of movement is from high to low
size of gradient impacts rate of uptake

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5
Q

How is facilitated DIFFERENT from passive

A

uses membrane-bound solute-specific carrier molecules
smaller concentration gradient is required for significant uptake (saturation effect)
effectively transports glycerol, sugars, and amino acids

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6
Q

Why is facilitated more prominent in Eukarya?

A

bacteria and archaea are typically found in nutrient-poor environments
they are mostly using active-transport

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7
Q

Saturation effect

A

diffusion rate reaches a plateau at higher concentration
the carrier/transporters will become saturated (full)

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8
Q

Example of gradient being maintained by transformation

A

GLUCOSE
phosphorylate glucose once it enters the cell
glucose will stay high outside because it is not in that form on inside

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9
Q

How does facilitated diffusion works

A

Carrier protein starts in outward-facing conformation
solute binds
binding causes conformation change- closes to outside and opens to inside
carrier protein is now in inward-facing conformation
releases solutes into the cell

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10
Q

Active transport

A

energy dependent process
move molecules against gradient
concentrated molecules into cell
involves specific carrier proteins

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11
Q

3 types of active transport

A

Primary active transport
Secondary active transport
Group translocation

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12
Q

Primary active transport

A

uses energy produced by ATP hydrolysis to move substances across concentration gradient
ABC transporters

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13
Q

Secondary active transport

A

couples the potential energy of ion gradients to transport solutes
uses potential energy in ion gradients and turns it into kinetic energy MFS transport

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14
Q

ABC transporters

A

ATP-Binding Cassette transporters
structure and function is highly conserved across bacteria, archaea, and eukaryotes
Uniport

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15
Q

what does ABC consist of

A

2 hydropobic membrane spanning transport proteins
2 cytoplasmic ATP binding domains

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16
Q

Uniport

A

transport 1 molecule at a time

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17
Q

How does ABC work?

A

Solute binds to solute binding protein
complex interacts with hydrophobic channel subunits
channel undergoes conformational change
ATP hydrolysis in ATP binding subunits provides energy
The channel opens and the solute moves into the cytoplasm

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18
Q

MFS transporters

A

Major Facilitator Superfamily
uses ion gradients to cotransport substances
Proton moves down its gradient so solute can move againts its gradient
symport and antiport

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19
Q

Symport

A

two substances both moving in same direction

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20
Q

antiport

A

two substances moving in opposite directions

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21
Q

symport example

A

E. coli- transport of lactose using lactose permease
transports lactose and proton simultaneously into cell

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22
Q

antiport example

A

E. coli- transport of sugars and amino acids
sugars and amino acids into the cell while pumping sodium out

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23
Q

PTS- group translocation

A

Phosphotransferase system
PEP + sugar (outside)–> pyruvate + sugar-phosphate (inside)
- PEP is high energy bond- when hydrolyzed it gives energy to system
- sugar is modified inside the cell
Also invovled in chemotaxis

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24
Q

Where is PTS found

A

faculative anaerobes
some obligate anaerobes

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25
Why is PEP not found in aerobes
Uses PEP for respiration they do not have alternative ways to generate PEP so they do not want to use it elsewhere
26
How does PEP work
Want to phosphorylate solute so it makes it imposible for it to move back out of cell E1 is conserved in all PTS organisms - acts as an intermediate to pass off phosphate from PEP Phosphate is transferred to incoming sugar by E2 E2 portion gives specificity - number and arrangement of subunit determens the carb that moves in
27
Siderophores
molecules with high affinity for ferric iron
28
Why do microorganisms secrete siderophores
Ferric iron is very insolube so uptake is difficult siderophores are secreted to aid in uptake
29
T/F siderophores are secreted all the time
FALSE only secreted when stores are low
30
Examples of siderophores
ferrichrome enterobactin
31
what happens once siderophores bind iron
whole complex is moved to primary active transport just iron may be released
32
How does PM capture energy
embedded electron transport chains help create Proton Motive Force (PMF)
33
What is PMF used for?
respiration and photosynthesis derive energy for motion (flagella)
34
PM and sensory systems
proteins in PM can detect environmental changes cell uses detected changes to alter gene expresion maybe bound to integral/peripheral membrane systems
35
T/F moving materials out of cell requires ATP energy
true
36
2 ways to move across plasma membrane
Sec system TAT (twin argine transport)
37
Sec system
requires energy Protein has signal at end terminal and SecB binds to protein SecB keeps protein from folding and brings it to SecYEG complex SecYEG forms the channel SecA hydrolyzes ATP Protein is moved out signal protein at the end is cleaved and protein folds
38
TAT
energy comes from potential energy in ion stores transports folded proteins Proteins have a 2 arginine end sequence
39
Which Gram bacteria has an easier time moving things out of cell?
Gram-positive
40
Gram-negative secretion
either one step or two step
41
one step Gram-negative secretion
Doesnt use TAT or Sec moves protein all the way across the PM then the outer membrane Types 1 and 3
42
Two step Gram-Stain secretion
Pick up proteins from Sec/TAT then moves them the rest of the way Types 2,4 and 5
43
Functions of cell wall
Maintains shape of bacterium helps protect from osmotic lysis helps protect from toxic material may contribute to pathogenicity
44
How does cell wall help maintain shape?
organization of peptidoglycan in juction with other things
45
How does cell wall contribute to pathogenicity
Specifically in Gram-negative pathogenic area within the cell Peptidoglycan has PAMPs
46
What are PAMPs?
pathogen-associated molecular pathways
47
Peptidoglycan structure of cell wall
mesh-like polymer of identical subunits forming long strands Two alternating sugar Penta/tetra peptide side chains of D and L amino acids 2 D-ala bonds which are important for cross linking
48
What are the two alternating sugars in peptidoglycan
N-acetylgulcosamine (NAG) N-acetylmuramic acid (NAM)
49
Penta/tetra peptide side chains
ALWAYS attached to NAM initially penta but after crossing they become tetra
50
Gram-Negative cross linking
Direct peptide cross link position at 2 and 3
51
Gram-positive cross link
indirect cross-link forms a pentaglycine interbridge
52
How do D-form of amino acids form?
Only L-from is naturally encoded Racernaces break bonds in L form to create D-from
53
Why are D-forms created
Helps protect cell wall against proteases/peptidases
54
How is peptidoglycan structure of cell wall made?
NAM is synthesized in cytoplasm NAM is linked to Bactoprenol and NAG is added to NAM Bacteroprenol flips NAM-NAG into periplasm disaccharides added to existing chain and cross-linking occurs due to transpeptidase Bactoprenol flips back into cytoplasm
55
What is bactoprenol?
a flipase
56
Effect of lysozyme secretions on cell wall
Targets the b, 1-4 glycosidic bonds and cleaves it leaving the peptidoglycan weak the cell can then lysis if osmotic gradient changes
57
Where do lysozyme secretions come from?
naturally secreted in our mucus, tears, sweat, etc.
58
Effect of lysostaphin
targets and cleaves inter-bridges in certain staphylococcus species only
59
what is b-lactam
antibiotic natural product produced by other bacterial
60
How do b-lactam antibiotics work?
their structure resembles the 2 D-ala transpeptidase can't distinguish and binds to b-lactam structure Forms an irreversible linkage and cross-linking cannot occur
61
How do bacteria develop b-lactam resistance?
Efflux pumps mutations in pore proteins- make pores too small so antibiotics cant move in Beta lactamases
62
Where are pore proteins located?
outer membrane of Gram-negative bacteria
63
What do b-lactamases do
High a high affinity for N and O bond in the peptidoglycan backbone no longer looks like D-ala and transpeptidase will not bind to it
64
Peptidoglycan is both...
rigid- comes form b-glycosidic bonds (in backbone) flexible- comes from cross linkages
65
Two types based on Gram-stain
Gram positive- thick layer of peptidoglycan Gram-negative
66
Peptidoglycan structure
lies just outside cell membrane it is porous forms helical strands has a backbone of two alternating sugars connected by b, 1-4 glycosidic bonds
67
How does penicillin work?
B-lactam antibiotic
68
How does augmentin work?
works together with amoxicillin Has clavulanic acid-beta lactam rings but no antibiotic activity It reacts with b-lactamase so they target it and leave amoxicillin alone
69
How vacomycin works?
non b-lactam cell wall inhibitor sits on 2 D-ala and binds them together transpeptidase cannot recognize and crosslink will not happen
70
Example for another antibiotic
One that targets siderophores
71
Why would you want an antibiotic that targets siderophores?
siderophores are not found in eukaryotic cells bacteria need iron to live

MCB 2610 (24 decks)

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