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Microbiology 1010 > Lecture 2- Transport across the cytoplasmic membrane > Flashcards

Lecture 2- Transport across the cytoplasmic membrane Flashcards

1
Q

what is the function of a cytoplasmic membrane?

A

to control what passes into and out of a cell

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2
Q

what kind of permeability is a cytoplasmic membrane?

A

selectively permeable (semi- permeable)
the cell plays an active role in determining its own selective permeability

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3
Q

why cant we just wait for everything to diffuse into a cell?

A

the cell will die because it takes so long to diffuse things into a cell. it isnt just necessarily about size, things are just hard to diffuse across a cell membrane

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4
Q

what normally uses passive diffusion?

A

water, oxygen, carbon dioxide

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5
Q

does water only use passive diffusion?

A

no, there are also aquaporins used to move water across a cell membrane

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6
Q

how is facilitated diffusion similar to passive diffusion? (3)

A
  1. movement of molecules is not energy dependent
  2. direction of movement is from high to low conc.
  3. size of concentration gradient impacts rate of uptake
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7
Q

how is facilitated diffusion different from passive diffusion? (3)

A
  1. uses carrier molecules
  2. smaller concentration gradient is required for significant uptake of molecules
  3. effectively transports glycerol, sugars and amino acids
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8
Q

not all bacteria are the same so what do the statements of facilitated diffusion have to do with that?

A

they are generalized statements!

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9
Q

what are characteristics of carrier- mediated transport systems? (2)

A

show saturation effect
highly specific

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10
Q

what does it mean to reach saturation in carrier- mediated transport systems?

A

take up all molecules it can
for example, it might be able to only take 4 molecules at once… therefore, if we give the carrier 20 molecules, it wont make the carrier protein move stuff into the cell any faster

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11
Q

what is facilitated diffusion?

A

diffusion with a carrier that is driven by concentration gradients

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12
Q

how much can a membrane transporter concentrate substance compared to the external environment?

A

1000 times (3x the magnitude)

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13
Q

what are the 3 classes of membrane transporters that have been identified?

A

uniporters
antiporter
symporter

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14
Q

what do uniporters do?

A

transport a substance from one side of a membrane to the other in one direction

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15
Q

what do antiporters do?

A

transport one substance across the membrane in one direction and a second molecule in the opposite direction

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16
Q

what do symporters do?

A

transport two molecules across the membrane in the same direction

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17
Q

what do antiporters and symporters have in common?

A

they are both cotransporters

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18
Q

transport requires energy, what are the two types of energy that are used?

A

ATP hydrolyzed to ADP
Proton motive force (PMF) coupled to transport (as a proton goes down conc. gradient, energy is generated to move a molecule against its conc. gradient)

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19
Q

what are the two major mechanisms with carrier proteins?

A

active transport
group translocation

20
Q

what is active transport?

A

energy dependent pumping system in which the substance being transported combines with a membrane bound carrier which releases the substance into the cell UNCHANGED

21
Q

why might you need to use active transport?

A

concentration of substance inside the cell is higher than outside the cell
ex. sugars, amino acids, organic acids, inorganic ions

22
Q

what is an example of a transporter that uses active transport?

A

ABC type transporters

23
Q

what is group translocation?

A

molecule is transported and modified during transport

24
Q

what is an example of group translocation?

A

PTS system

25
Q

in lac permease of E. coli, how is lactose transported into E.coli?

A

simple transporter lac permease that is a symporter (transports lac permease and H+ into the cell simultaneously)
is therefore energy driven

26
Q

what does ABC transport stand for?

A

ATP binding casette

27
Q

what are the most known large families that are apart of ABC transport?

A

B. subtilus
E. coli

28
Q

what do ABC transporters do?

A

uptake organic compounds (sugars, amino acids), inorganic nutrients (sulfate, phosphate) and trace metals

29
Q

is ABC transport active or passive? is it specific or not?

A

active
high specificity

30
Q

what is the difference between gram- negative bacteria and gram- positive bacteria in ABC transport?

A

gram- negatives: have periplasmic- binding proteins and ATP driven transport proteins
gram positives: have substrate- binding lipoproteins and ATP driven transport proteins

31
Q

what are the 3 components to ABC transporters?

A

periplasmic binding protein
integral membrane protein
ABC protein that provides ATPase function

32
Q

how does a solute enter a gram negative bacteria? (6)

A

solute
periplasmic space
solute binds to solute binding protein
binding protein + solute bind to the binding site on the integral membrane protein
solute is released to integral membrane protein and protein goes down the permease channel
ATP turns into ADP (because one phosphate was used to get solute into cell)

33
Q

what does the hydrolysis of ATP by ABC protein provide?

A

energy for translocation of solute

34
Q

what are the 3 major transport systems in prokaryotes?

A

simple transport
ABC transporter
group translocation

35
Q

what energy does simple transport use?

A

proton motive force

36
Q

what energy does ABC transport use?

A

ATP

37
Q

what energy does group translocation use?

A

phosphoenolpyruvate

38
Q

how is group translocation different from ABC transport?

A

substance is chemically altered during uptake across a membrane

39
Q

what does it mean when a substance is altered during translocation?

A

high concentration of the original substance does not build up in the cell, therefore this favors overall diffusion in the cell (transporting with the gradient)

40
Q

what transport system uses the PTS system?

A

group translocation

41
Q

what is the PTS system?

A

phospho relay that results in the phosphorylation and transport of a compound

42
Q

what is something unique that the PTS system does?

A

can help choose the best carbon source available
ex. for E. coli there is an option to use glucose or lactose, the PTS system tells it to use all the glucose first because its a better carbon source

43
Q

what is the overall reaction of the phosphotransferase system?

A

PEP (into cell) + carbohydrate (out of cell)
–>
pyruvate (into cell) + carbohydrate–P (into cell)

44
Q

what are the 5 components of the PTS system? where are they located?

A

EI (enzyme I) in cytosol
HPr (histidine protein) in cytosol
IIA (enzyme IIA) in cytosol
IIB (enzyme IIB) in cytosol or membrane
IIC (enzyme IIC) membrane

45
Q

how does group translocation work with ex. phosphotransferase system in E. coli?

A
  1. PEP donates P to a phosphorelay system
  2. P is transferred through a series of carrier proteins (EI, HPr, IIA, IIB, IIC) and deposited onto the glucose as it is brought into the cell
  3. sugar is phosphorylated during transport across the membrane

Microbiology 1010 (19 decks)

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