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BCH210 > Membranes protein structure > Flashcards

Membranes protein structure Flashcards

1
Q

what are the essential functions of membranes

A

they act as barriers and also support localization of the cell so it can do lots of different things in different places

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2
Q

what mediates signaling across membranes

A

proteins and lipids

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3
Q

what allows for the cell membrane to regulate cell-cell communication

A

glycoproteins and glycolipids

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4
Q

what is responsible for membrane formation

A

a decrease in ionic interactions with water. this is basically the hydrophobic effect

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5
Q

are membranes asymmetrical or symmetrical

A

they are asymmetrical composed of lipids and proteins

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6
Q

what mediates the process of proteins carrying molecules and signals being transmitted across the membrane

A

conformation changes

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7
Q

____ and ____ play an important role in membrane fluidity

A

lipids and cholesterol

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8
Q

What recent modifications have been made to the fluid mosaic model

A

the movement of lipids is restricted based on if they are in pure lipids or biological membranes

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9
Q

What technique is useful in measuring membrane movement

A

FRAP (fluorescence recovery after photobleaching)

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10
Q

lipid raft

A

area in the membrane where lipids tend to hang out for a longer period of time

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11
Q

What does the addition of sugars and proteins to the membrane post-translationally impact?

A

cell recognition and membrane insertion

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12
Q

Flip-Flop diffusion

A

movement of lipids from one leaflet to the other

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13
Q

is flip flop diffusion energetically favourable or unfavourable?

A

unfavourable

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14
Q

How do enzymes mediate membrane asymmetry

A

by creating active sites and spaces on the membrane

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15
Q

Flippase

A

ATP dependent translocase that moves lipids to the inner leaflet

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16
Q

Floppase

A

contains an active site and it moves things to the outer leaflet

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17
Q

Scramblase

A

ATP independent enzyme that is less specific and will be used to even out the lipids across the membrane. Moves all lipids down their concentration gradient
ensures that there is not too much flipping or flopping and the lipids are unbalanced

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18
Q

Lipids

A

molecules involved in providing structural support for cells and organelles

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19
Q

what defines classes of lipids

A

their physical properties, ie. whether they are hydrophobic or amphipathic

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20
Q

What type of lipids are involved in metabolism

A

triacylglycerides (carbon storage)

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21
Q

what lipids are important for the structure of membranes

A

phospholipids
sphingolipids
glycolipids
sterols

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22
Q

at physiological pH will fatty acids be deprotonated or protonated

A

deprotonated because its pka<pH

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23
Q

what is a saturated fatty acid

A

this is a fatty acid with single bonds

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24
Q

what is an unsaturated fatty acid

A

contains double bonds

25
Q

what is the usual numbering of double bonds in fatty acids

A

they are numbered relative to the carboxylic acid but it can also be named relative to the methyl group for omega fatty acids

26
Q

Fatty acid nomenclature

A

C’s : # of double bonds

27
Q

what makes a fatty acid an omega fatty acid ?

A

the location of the double bond. a fatty acid is considered an omega fatty acid when the double bond is situated three or six carbons away from the methyl group

28
Q

what does delta refer to?

A

this is when we label carbons relative to the carboxylic group

29
Q

What are considered the good fats

A

unsaturated and omega fats

30
Q

what type of fats decrease membrane fluidity

A

saturated fats because they form lots of non-covalent bonds that act like glue

31
Q

What about unsaturated fats increase membrane fluidity

A

they have kinks that participate in cis double bonds, increasing fluidity by causing there to be more room in the membrane

32
Q

what does a higher melting temperature of lipids mean?

A

a higher Tm means that there are more covalent bonds that need to be broken

33
Q

if a membrane has a higher Tm does it mean it is more or less fluid?

A

it would be less fluid because a higher temperature means it is more rigid and contain more non-covalent interactions that need to be broken down

34
Q

Tri-acyl-glycerols (TAGs)

A

3 fatty acids attached to a glycerol

35
Q

what attaches the fatty acids to the glycerol

A

ester linkage

36
Q

what are tags good for

A

they are good for storing carbon that can be used for energy

37
Q

how are amphipathic molecules made?

A

By attaching fatty acyl chains to polar (OH, sugar, or phosphate) head groups

38
Q

what is the most common steroid found in membranes?

A

hydrophobic cholesterol

39
Q

Glycerophospholipids

A

they contain 2 fatty acid tails with a glycerol head and a phosphate group

40
Q

examples of glycerophospholipids

A

phosphatidylethanolamine (PE) and PS.

these bind to flippase

41
Q

sphingolipids

A

lipids that contain 1 fatty acid bounded to N on sphingosine

42
Q

examples of sphingolipids

A

sphingomyelin and gangliosides

43
Q

cholesterol

A

can be metabolized to other hormones needed for dietary lipid absorption

can form lipid rafts

44
Q

three types of membrane lipids

A

glycerophospholipids, sphingolipids, and cholesterol

45
Q

peripheral membrane proteins

A

located on the outside of the membrane that either interacts with outer or inner leaflets by non-covalent interactions

46
Q

Integral membrane proteins

A

span membrane

47
Q

what is the difference between peripheral and integral proteins

A

removal

48
Q

how can peripheral membrane proteins be removed

A

by milder conditions like increasing salt in pH

49
Q

how are integral membrane proteins removed

A

through more harsh conditions like detergents that break apart the membrane

50
Q

how are lipid anchored proteins removed? why?

A

they also require harsher detergents because their tails are covalently attached to the amino side chains and functional groups

51
Q

for membrane proteins what extra steps are taken during protein purification

A

adding detergents

52
Q

Critical micelle concentration (CMC)

A

concentration at which the detergent spontaneously forms stable micelle structures

53
Q

what does it mean for a concentration above CMC

A

sufficient enough for you to extract protein from membrane

54
Q

how can you predict membrane spanning segments

A

by scanning primary sequences for long stretches of hydrophobic amino acids that represent TM segments

55
Q

hydropathy scale

A

takes into consideration factors about amino acids that could indicate transmembrane segments

56
Q

why does a negative hydropath index indicate

A

more polar segments

57
Q

what does a positive hydropathy index indicate

A

more non-polar/hydrophobic segments

58
Q

how can you read a topology chart to indicate a transmembrane protein

A

high peaks that are 20 amino acids wide

BCH210 (11 decks)

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