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BIOC3021 > lecture eleven - lipids and membranes > Flashcards

lecture eleven - lipids and membranes Flashcards

1
Q

lipids

A

soluble in non-polar solvents, highly hydrophobic, most reduced class of biological compounds, release energy upon oxidation

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2
Q

sterols

A

hormones, perhydrocyclopentanophenanthrene ring structure
NOT aromatic, NOT planar

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3
Q

fatty acids

A

linear hydrocarbons with one carboxyl group at one end and many methylene groups in the side chain
12-24 C
hydrophobic character increases with chain length
double bonds increases the solubility of the compounds in water and decrease their melting point

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4
Q

triaglycerols

A

MAJOR STORAGE of lipids
3 fatty acids esterified to glycerol
relatively non-polar, highly reduced (saturated)

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5
Q

phosphoglycerols

A

membrane components
2 fatty acids, glycerol, phosphate, ionic or polar alcohol
fatty acid at 1 position = saturated
fatty acid at 2 position = unsaturated
phosphatidyl choline is the derivative

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6
Q

sphingolipids

A

membrane functions
similar in overall structure of phosphoglycerols

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7
Q

polyisoprenoid

A

vitamin A and beta-carotene
resembles polymers of isoprene but have a very different biochemical origin

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8
Q

energy storage =

A

triaglycerols

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9
Q

membrane components =

A

phosphoglycerol

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10
Q

hormones =

A

sterols

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11
Q

biological detergents =

A

bile acids

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12
Q

insulating material =

A

phospholipid and sphingomyelin

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13
Q

vitamins =

A

polyisoprenoid

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14
Q

highly hydrophobic (non-polar) so can be extracted into non-polar solvents

A

fatty acids

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15
Q

what characteristics determine the melting point and water solubility of a fatty acid

A

melting point increases with chain length
double bonds decrease melting points & increase solubility
at temperature below the melting point, they will be solid
above melting point, exhibit fluid character

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16
Q

functions of fatty acids

A

major energy storage material
critical part of biological membranes
lipid derivatives function as hormones
other derivatives are biological detergents

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17
Q

triglycerols consist of

A

3 fatty acids esterified to glycerol

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18
Q

phosphatidic acid has

A

2 fatty acids esterified to glycerol

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19
Q

saturated fatty acid

A

do NOT have double bonds, linear zig-zag structure, are solid at room temperature

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20
Q

monounsaturated fatty acid

A

1 double bond, 1 unit of unsaturation

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21
Q

polyunsaturated fatty acid

A

2+ double bonds

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22
Q

how do double bonds change the structure of a fatty acid from a linear to bent form?

A

unsaturated fatty acids tend to be in the “cis” configuration where the chain continues at a new angle, resulting in a bend

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23
Q

mono and polyunsaturated fatty acids contribute to

A

the liquid nature of membranes

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24
Q

how are trans isomers formed during the chemical hydrogenation of unsaturated fatty acids?

A

hydrogenation increases lipid solubility, double bonds are converted to single bonds

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25
Q

how do trans fatty acids influence human health?

A

trans fatty acids have double bond in trans configuration and this has been shown to increase the risk of CAD

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26
Q

major storage of fatty acid in humans

A

triacylglycerols

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27
Q

how are triacylglycerols broken down in the intestine? where are they reassembled? where are they taken?

A

broken down in the lumen of the intestine
component fatty acids and monoacylglycerols

are taken up into the intestinal epithelial cells - where triacylglycerols are reassembled then released in the lymph, and are transported through chylomicrons to adipose cells

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28
Q

where are triacylglycerols stored?

A

in adipocytes, until there is a need for energy

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29
Q

phosphoglycerols

A

related to triacylglycerols, but the third carbon is connected to a phosphate residue
fatty acid at the first carbon tends to be saturated
fatty acid at the second carbon tends to be unsaturated
hydroxyl group at the third carbon is connected to the phosphate

30
Q

major physiological function of phosphoglycerols

A

serve as membrane components; important to contain unsaturated fatty acids – the fatty acids contribute to the fluid mosaic structure of membranes

31
Q

phosphatidyl choline

A

lecithin; carries a positive permanent charge, isn’t affected by pH

32
Q

phosphatidyl ethanolamine

A

alcohol derivative, amine group is positively charged at physiological pH

33
Q

phosphatidyl inositol

A

polyhydroxyl compound, highly polar but uncharged

34
Q

phosphatidyl serine

A

has positively charged amine and negatively charged carboxyl

35
Q

how do sphingomyelin compounds differ from phosphoglycerols?

A

sphingosine replaces glycerol; provides HC chain and a long chain FA
amide linkage provides a second HC chain
has phosphate and polar alcohol

36
Q

cerebrosides

A

sphingolipids that have glucose or galactose instead of phosphate and choline
brain and nervous tissues

37
Q

gangliosides differ from cerebrosides in that…

A

the carbohydrate component is more complex and varied

38
Q

why is it important for the fluid mosaic membrane to contain phospholipids that are rich in unsaturated fatty acids?

A

unsaturated fatty acids contribute to the fluidity of the membrane and allow proteins to diffuse in a lateral direction, and associate/interact in a functional manner

39
Q

basic structure of cholesterol

A

class of sterols with perhydrocyclopentanophenanthrene ring; NOT aromatic, NOT planar
precursor of bile acids and sterol hormones

40
Q

derived from cholesterol, act as biological detergents

A

bile salts

41
Q

bile salts

A

stored in the gallbladder, released when lipids are metabolized
break lipids up into smaller particles, making triglycerol compounds more accessible to lipase enzymes

42
Q

common steroid hormones derived from cholesterol

A

progesterone, testosterone, estradiol

43
Q

prostaglandins

A

lipids that are synthesized in complex pathways from arachidonic acid; have hormone-like functions for short time periods

44
Q

NSAIDs block…

A

prostaglandins to reduce pain

45
Q

how and why do phospholipids form vesicle bilayers and what are the characteristics of these bilayers?

A

interior of bilayers tend to be hydrophobic, vesicles are formed that carry water through the membrane
polar and non-polar regions; water-filled spherical lipid bilayers

46
Q

vesicle bilayers function as

A

artificial cells and can transport molecules across mammalian membranes

47
Q

micelle

A

no water inside, hydrophobic interior

48
Q

vesicles

A

water-filled interior

49
Q

the key component of fluid mosaic model

A

polyunsaturated fatty acids in membrane phospholipids

50
Q

movement of fluid mosaic model protein molecules

A

fluidity allows them to diffuse laterally, but they do not rotate

51
Q

features of fluid mosaic model

A

phospholipid and glycolipid molecules mosaic of non-polar protein molecules that are embedded in the membrane bilayer
bilayer serves as permeability barrier for polar and ionic membrane and as SEMI-fluid solvent for integral membrane protein
protein diffuse in lateral direction in the plane of the membrane, but do not rotate (flip-flop)

52
Q

components of FMM

A

phospholipid bilayer
integral proteins (immersed in the non-polar core)
peripheral proteins are found attached to both faces of bilayer
cholesterol immersed in the non-polar interior of the bilayer
glycolipid and glycoprotein on the outer, extracellular face of the membrane

53
Q

inner leaflet of FMM

A

tend to have phospholipids with net negative charge

54
Q

outer leaflet of FMM

A

phospholipids tend to be neutral

55
Q

FMM membrane asymmetry is for…

A

cell homeostasis

56
Q

how do components of fluid membranes diffuse?

A

membrane proteins and lipids diffuse laterally in the plane of the membrane; do NOT rotate from one side to another

57
Q

complex carbohydrates are found where on the membrane

A

extracellular face, attached to glycoproteins and proteoglycans

58
Q

why are phospholipids distributed asymmetrically in the membrane and what is the consequence of this distribution?

A

inner leaflet is rich in phospholipid with net (-) charge
outer leaflet has neutral phospholipids
consequence = different charges

59
Q

integral membrane proteins (location and removal)

A

immersed in nonpolar interior of the membrane with high % of nonpolar amino acids
difficult to remove from the membrane, need detergents

60
Q

peripheral proteins (location and removal)

A

not immersed in the interior of membrane, attached to outer face by various interactions; can be removed with mild treatments, relatively polar and don’t need stabilizer

61
Q

in what ways is the protein glycophorin typical of integral membrane proteins?

A

has a series of hydrophobic amino acids that are immersed in the membrane with alpha-helical conformation

62
Q

what part of the glycophorin protein are hydrophobic? which is hydrophilic?

A

single-membrane spanning alpha-helix that is highly hydrophobic
the outside of glycophorin is mostly hydrophilic amino acids and water-soluble, with carbohydrates attached
the inside of glycophorin is hydrophilic amino acids with no carbohydrate attached

63
Q

what is a hydropathy plot, and what do such plots tell us about membrane proteins such as glycophorin?

A

measures the occurrence of its hydrophobic, membrane-spanning alpha helix structures
non-polar amino acids exhibit (+) values
used to construct models of membrane proteins
10 amino acids at a time, starting from the terminal end

64
Q

what types of compounds can pass through a biological membrane using simple diffusion

A

small, non-polar molecules and gases
ex: O2, CO2, N, urea, ethanol

65
Q

simple diffusion

A

no energy or help needed
diffusion from high to low concentration
not saturated, not sensitive to inhibitors

66
Q

facilitated diffusion

A

move through a protein tunnel, still with no energy needed
sugars, amino acids, ions, nucleotides, and water diffuse this way

67
Q

molecular characteristics of the integral membrane protein transport systems

A

calcium-ATPase transport calcium ions across mammalian membranes
non-polar with lots of non-polar amino acids

68
Q

active transport system

A

substrate moves through a tunnel with energy, low to high concentration

69
Q

primary active transport

A

directly coupled to ATP hydrolysis, against a concentration gradient,
direct coupling to an energy source
saturable and sensitive to inhibitors

70
Q

secondary active transport

A

energized by ion gradients (Na+ or K+)
first established by a primary system, then indirectly coupled to ATP hydrolysis
saturable and can be inhibited

71
Q

SYMport

A

part of secondary active transport; couple the downhill flow of one species to energize the uphill flow of another in the SAME direction across the membrane

72
Q

ANTIport

A

part of secondary active transport; couple the downhill flow of one species to energize the uphill flow of another in the OPPOSITE direction across the membrane

BIOC3021 (6 decks)

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