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MBIO1010 > Lecture Set 2 : Part 1 > Flashcards

Lecture Set 2 : Part 1 Flashcards

1
Q

what is contained within the bacterial cell envelope?

A

-cytoplasmic membrane
-cell wall
-periplasm

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2
Q

what is the cell wall?

A

-rigid layer that gives structural strength and integrity

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3
Q

what is the periplasm?

A

-space between the cytoplasmic membrane and the cell wall

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4
Q

what is the cytoplasmic membrane?

A

-thin structure that surrounds the cell
-vital barrier in separating the cytoplasm from the outside environment

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5
Q

what are some characteristics of the cytoplasmic membrane?

A

-physically rather weak, but it works for its functions
-highly selective semi-permeable barrier (creates concentration gradients of specific metabolites and allows for the excretion of waste)

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6
Q

what is the standard structure of the bacteria and eukarya cytoplasmic membrane?

A

-composed of a phospholipid bilayer
-has ester linked phospholipids

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7
Q

what does a phospholipid consist of for bacteria and eukarya?

A

-1 glycerol backbone
-2 fatty acid tails
-1 phosphate and a variable side chain/head group (ex: ethanolamine)

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8
Q

what are special about phospholipids?

A

-they have hydrophobic tails (fatty acid/isoprene)
-hydrophilic head regions (glycerol + phosphate)
-therefore they are amphipathic

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9
Q

what does it mean to be amphipathic? what does this allow for the phospholipids to do?

A

-have both polar and non-polar characteristics
-phospholipids naturally orient into bilayers when in water

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10
Q

how does a phospholipid bilayer work?

A

-fatty acid tails point inward (form a hydrophobic core)
-polar head groups remain exposed to water in the external environment or cytoplasm
-called a true unit membrane (true bilayer)

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11
Q

how thick is a phospholipid bilayer?

A

-8-10nm

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12
Q

what are the inner and outer leaflets of the bilayer?

A

-inner leaflet = closest to cytoplasm
-outer leaflet = closest to external environment

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13
Q

what are the different membrane proteins?

A

-integral membrane proteins
-transmembrane proteins
-peripheral membrane proteins

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14
Q

what are integral membrane proteins?

A

-apart of the structural integrity of the membrane
-firmly embedded into the membrane
-amphipathic

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15
Q

what are transmembrane proteins?

A

-type of integral membrane protein
-extend completely across the membrane

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16
Q

how are integral membrane proteins amphipathic?

A

-have a hydrophilic region that lies outside the membrane (external environment or cytoplasm)
-have a hydrophobic region that is buried inside the membrane

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17
Q

what are peripheral membrane proteins?

A

-proteins loosely associated with the membrane (only on one side)
-may have a lipid portion
-may interact with integral proteins

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18
Q

what are peripheral membrane proteins that have a lipid portion called?

A

-lipoproteins

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19
Q

how do peripheral membrane proteins interact with integral membrane proteins?

A

-interact for energy metabolism and transport
-can bind to the other membrane proteins

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20
Q

what do peripheral membrane proteins also associate with?

A

-phospholipid head groups

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21
Q

how do membrane proteins work together?

A

-group together in clusters to carry out a function

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22
Q

what is the ‘fluid mosaic’ model?

A

-cytoplasmic membrane exists in a semi fluid state
-lipids in the outer leaflet are different than lipids in the inner leaflet (diff. head groups + fatty acid tails)
-integral proteins can move laterally but not switch sides
-its composition can change to suit conditions

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23
Q

how do the phospholipid linkages differ between bacteria, eukarya, and archaea?

A

-archaea have ether linked phospholipids (single bonded)
-bacteria and eukarya have ester linked phospholipids (double bonded)

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24
Q

what is the standard structure of the archaea’s cytoplasmic membrane?

A

-composed of a phospholipids (bilayer or monolayer)
-has ether linked phospholipids
-no fatty acid tails (hydrocarbon tails from repeating isoprene units)

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25
what is isoprene?
-5-carbon hydrocarbon
26
what are the phospholipids that create a bilayer in archaeal membranes?
-glycerol diether phospholipids -isoprene tails are long branched tails called phytanyl
27
what are the phospholipids that create a monolayer in archaeal membranes?
-diglycerol tetraether phospholipids -2 phospholipids joined by the tails (biphytanyl) -has 2 ends so it does not orient as a bilayer -makes up the inner and outer faces of the membrane
28
what advantage do lipid monolayers have?
-extremely heat resistant -good for archaea living in extreme environments
29
what archaea have lipid monolayers?
-hyperthermophilic (high heat loving) archaea -grow best at 80 degrees celcius
30
what are the 3 main functions of membranes?
-permeability barrier -protein anchor -energy conservation
31
how does a membrane act as a permeability barrier?
-nutrient and waste transport -small non-polar molecules can diffuse easily across the membrane -large or polar molecules must be moved by transport proteins (integral proteins)
32
do peripheral proteins help in transport?
-they do not span across the entire membrane so they can only help with movement on their one side
33
how does the membrane act as a protein anchor?
-holds proteins in place
34
how does the membrane help in energy conservation?
-generates and dissipates the proton motive force (gradient of protons across the membrane)
35
how does small non-polar molecules cross the membrane?
-passive diffusion (high to low concentration) -ex: 02, CO2
36
how do large and polar molecules cross the membrane?
-cannot diffuse across the membrane -require transport proteins
37
what is an example of a molecule that can passively diffuse across the membrane but is often transported using a protein to speed diffusion?
-water -transported with aquaporins -even though it is polar, it is still small enough
38
what are examples of molecules that can pass through the membrane well?
-water -glycerol
39
what are examples of molecules that cannot pass through the membrane well and require transport proteins?
-trytophan (large) -glucose (large) -Cl- (charge) -K+ (charge) -Na+ (charge)
40
what is facilitated diffusion?
-integral proteins that allow specific molecules to diffuse across the membrane -moving from high to low [] -no energy is required -used to speed up the rate of diffusion
41
what is an example of facilitated diffusion?
-E. coli's aquaporin -helps water diffuse more efficiently
42
what is active transport?
-highly specific transport proteins accumulate solutes against a concentration gradient -requires energy -moves from low (outside the cell) to high (inside the cell) []
43
what is the significance of being able to move solutes against their concentration gradient?
-allows for solute [] to be sufficient fro biochemical processes of microbes
44
what is active transport subject to?
-saturation effect -limit to the rate of transport -if all carriers/pumps are fully engaged they cannot move more solute even if the solute [] increases -rate has a maximum
45
how are the transport proteins in active transport highly specific?
-they will usually only carry a single kind of molecule
46
what are the 3 types of active transporters?
-simple transporters -group translocation -ABC transportation systems
47
what is a simple transporter?
-a single transmembrane protein used for transport -energy comes from the proton motive force -2 types
48
what are the 2 types of simple transporters?
-symport -antiport
49
what is a symport?
-simple transporter where both molecules (proton and substrate) are moving in the same direction across the membrane -movement of one molecule provides the energy required to move the other molecule
50
what is an example of a symport?
-E.coli's lactose permease -transports lactose and a H+ into the cell simultaneously -energy stored in the proton gradient is used to transport lactose into the cell
51
what is an antiport?
-simple transporter where each molecule (proton and substrate) are moving in opposite directions across the membrane -movement of one molecule provides the energy required to move the other molecule
52
what is an example of an antiport?
-E.coli's sodium transport system -allows H+ to move into the cell while pumping Na+ out of the cell -energy stored in the proton gradient is used to transport Na+ out of the cell
53
what is group translocation?
-a series of proteins that carry out a single transportation event -substrate is modified as it is brought into the cell (only form of active transport with chemical modification of the substance being transported -energy component is a high-energy organic compound
54
how is group translocation different from simple transport?
-substance being transported is chemically modified -energy component is a high-energy organic compound
55
what is an example of group translocation?
-E.coli's phosphotransferase system (PTS) -phosphoenolpyruvate (PEP) donates a PO4 3- group to a phosphorelay system -PO4 3- moves through a series of protein carriers until it is deposited onto a sugar as it is brought into the cell (chemically modifying)
56
does the sugar being chemically modified affect the concentration gradient?
-NO
57
where does PEP come from?
-glycolysis -intermediate (gives up its phosphate to become pyruvate)
58
what are the different protein carriers involved in the PTS?
-Enz I (non-specific) -HPr (non-specific) -Enz II a (specific) -Enz II b (specific) -Enz II c (specific)
59
what is the distinction between specific and non-specific components of the PTS group translocation?
-non - specific components act as general machinery -specific components are specific to a particular sugar
60
what type of proteins are in the PTS group translocation?
-Enz I, HPr, and Enz II a are cytoplasmic proteins (inside the cell) -Enz II b is a peripheral membrane protein -Enz II c is a transmembrane protein
61
what is happening to all of the proteins in the PTS group translocation?
-they are getting phosphorylated until the phosphate reaches Enz II c -this is when glucose can now enter the cell
62
what are the 3 components of ABC transporters?
-periplasmic solute binding protein (gram - cells) -lipid anchored protein (gram + cells) -integral membrane protein (transmembrane) -ATP binding protein (energy component)
63
what is the role of the periplasmic solute binding protein/lipid anchored protein?
-binds to a specific substrate and carries it to the membrane for transport
63
what is the role of the integral membrane protein (transmembrane)?
-transports substrate across the membrane
63
how does the ATP binding protein provide energy?
-hydrolyzes ATP to power the transport -2 ATP are hydrolyzed to form 2 ADP and 2 inorganic phosphates
64
what are ABC transporters used to transport?
-some sugars, amino acids, inorganic nutrients (SO4 2- and PO4 3-), and trace metals
65
what is special about ABC transporters?
-have high substrate specificity (1 substrate per ABC transporter) -this allows them to extract trace amounts of things -they can concentrate substrates inside the cell even when concentration outside is extremely low
66
how can we describe ABC transporters ability to extract trace amounts of things?
-passive transport cannot extract specific nutrients if they are limited -using energy and a highly specific transporter allows for this to be done (transporter is only able to transport 1 thing) -lets metabolic needs be met
67
how does the high specificity of ABC transporters affect bacterial growth?
-allows bacteria to grow in environments that seem to be lacking in nutrients

MBIO1010 (28 decks)

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