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MCDB 110 > Lipids and Membranes > Flashcards

Lipids and Membranes Flashcards

1
Q

what are functions of lipids?

A

a)membrane components (phospholipids, sphingolipids, glycolipids, sterols)
b)energy storage: triglycerides
c)digestion: bile acids
d)biological signals: prostaglandins, hormones, 2nd messengers
e)other: pigments, waxes, vitamins, scents

soluble in non-polar solvents

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2
Q

fatty acids

A

-components of membranes and triglycerides
-polar and nonpolar components (amphipathic)

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3
Q

triaclycerols (triglycerides)

A

storage form of fatty acids
-provides energy reserves
-fatty acid esters of glycerol

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4
Q

saponification

A

hydrolysis of fatty acids onto glycerol

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5
Q

phospholipids

A

-contains one phosphate group (with -X) and 2 fatty acids

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6
Q

sphingolipids

A

-membrane lipids
-contains sphingosine, fatty acid, and phosphate group (with -X)
-resemble phospholipids

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7
Q

waxes

A

esters of long chain fatty alcohols
-lanolin, carnauba wax, spermaceti oil, coatings of fruits
-hydrophobic barrier

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8
Q

sterols

A

components of eukaryotic membranes
-contains an hydroxyl group

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9
Q

steroid hormones

A

contains a ketone

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10
Q

bile acids

A

digestive “detergents”
-breaks down fat

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11
Q

prostaglandin

A

-inflammation
-blood vessel contraction
-pain/fever
-uterine contraction
-sleep/wake cycle

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12
Q

“fat soluble” vitamins

A

vitamin A,D,E,K are lipids

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13
Q

terpenes

A

isoprene derivative ->scents

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14
Q

functions of biological membranes

A

-selective permeability barrier
-organize complex reactions
-intracellular compartmentalization
-sensory transduction/amplification

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15
Q

how do membrane lipids assemble?

A

-they self assemble
-fatty acids are wedge-shaped->form micelles
-membrane lipids are cylindrical->form vesicles (lipid bilayer)
-spontaneous assemble (favorable deltaG)
->hydrophobic interactions, Vanderwaals, h-bonds
->increase entropy of water

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16
Q

what are important properties of membranes?

A

1)self-sealing
2)highly impermeable to polar or charged molecules (except for water)

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17
Q

integral proteins

A

-embedded in lipid bilayer
-firmly held in membrane by hydrophobic interactions
-removable only by detergent

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18
Q

peripheral proteins

A

-loosely bound to external position of membrane
-removable by high salt, urea, etc.
-easily removed

19
Q

lipid “anchored” proteins

A

-peripheral but covalently bound to a membrane lipid

20
Q

polytopic

A

protein goes through both leaflets of membrane

21
Q

monotopic

A

protein goes through one leaflet of membrane

22
Q

detergents

A

solubilize and disrupt membranes
-hydrophobic domains become coated with detergents
-pulls off integral and peripheral membranes

23
Q

fluid mosaic model of membranes

A

Singer Nicholson
- integral proteins->”icebegs” floating in 2D lipid “sea”
-fluid structure
Evidence:
1)lipids diffuse rapidly in plane of membrane (laterally) (within 1 leaflet)
2)integral membrane proteins diffuse rapidly

24
Q

membrane asymmetry

A

-proteins have unique orientation
-composition of lipids differs btwn 2 “leaves” of bilayer

25
Q

maintenance of asymmetry

A

-transverse diffusion of lipids is very slow
-transmembrane proteins don’t “flip”

26
Q

flippase

A

transport of lipids towards the cytoplasm and requires ATP
-against concentration gradient

27
Q

floppase

A

transport of lipids away from the cytoplasm and requires ATP
-against concentration gradient

28
Q

scramblase

A

bi-directional, non-energy dependent transport of lipids
-movement down concentration gradient

29
Q

membrane rafts

A

-enriched in sphingolipids and cholesterol
-everything on raft stays, but raft can move as one unit through the membrane

30
Q

how is membrane fluidity affected by temperature?

A

low temp->paracrystalline, more solid, thicker, risks breaking
high temp->leaky and porous, thinner

31
Q

other factors affecting membrane fluidity?

A

1) degree of saturation
-increase of saturation->decrease fluidity
2) length of fatty acid tail
-increase length->decrease fluidity
3)sterol content

32
Q

how do sterols plasticize the membrane?

A

high temp-> sterols decrease fluidity
-rigid sterol molecule restricts movement of lipid tails
-decreases fluidity

low temp-> sterols increase fluidity
-sterols prevents “crystalization” of membrane by blocking interactions btwn tails

33
Q

diffusion

A

movement from higher to lower concentration (no energy required)

34
Q

simple diffusion

A

movement of molecules from high to low through semipermeable membrane

35
Q

facilitated diffusion

A

“passive” transport protein-mediated using channels and carrier proteins

36
Q

active transport

A

transport against concentration gradient (requires energy)
-protein “pumps” mediate

37
Q

channels

A

-hydrophilic pores
-high capacity
-nonsaturable
-lower free energy barrier for movement of polar molecules across

38
Q

carriers

A

-permeases/transporters
-undergo conformational change
-saturable
-slower than channel proteins

39
Q

glucose permease

A

-a carrier
-specific to D-glucose
-reversible passive transport

40
Q

ligand gated channels

A

depolarization: Na+ and charge binds to channel, channel opens

41
Q

voltage-gated channels

A

self-propagating depolarization in muscles and nerve terminal
-static triggers the opening of channels

42
Q

primary active transport

A

-transporters pump molecules against concentration gradient
-pumping coupled directly to use of energy source
-Na+/K+ ATPase pump
-ATP hydrolysis induces change in confirmation

43
Q

Na+/K+ ATPase

A

-creates ion gradient
-creates charge gradient
-provides energy for secondary transport systems
2K+ in, 3N+ out

44
Q

secondary active transport

A

-energy stored in ion gradients drives transport of other molecules
-symporter (move in same direction)
-antiporter (move molecules in opposite directions)

MCDB 110 (5 decks)

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