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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
how do trans fatty acids influence human health?
trans fatty acids have double bond in trans configuration and this has been shown to increase the risk of CAD
26
major storage of fatty acid in humans
triacylglycerols
27
how are triacylglycerols broken down in the intestine? where are they reassembled? where are they taken?
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*
28
where are triacylglycerols stored?
in adipocytes, until there is a need for energy
29
phosphoglycerols
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
major physiological function of phosphoglycerols
serve as membrane components; important to contain unsaturated fatty acids -- the fatty acids contribute to the fluid mosaic structure of membranes
31
phosphatidyl choline
lecithin; carries a positive permanent charge, isn't affected by pH
32
phosphatidyl ethanolamine
alcohol derivative, amine group is positively charged *at physiological pH*
33
phosphatidyl inositol
polyhydroxyl compound, highly polar but uncharged
34
phosphatidyl serine
has positively charged amine and negatively charged carboxyl
35
how do sphingomyelin compounds differ from phosphoglycerols?
sphingosine replaces glycerol; provides HC chain and a long chain FA amide linkage provides a second HC chain has phosphate and polar alcohol
36
cerebrosides
sphingolipids that have glucose or galactose instead of phosphate and choline *brain and nervous tissues*
37
gangliosides differ from cerebrosides in that...
the carbohydrate component is more complex and varied
38
why is it important for the fluid mosaic membrane to contain phospholipids that are rich in unsaturated fatty acids?
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
basic structure of cholesterol
class of sterols with perhydrocyclopentanophenanthrene ring; NOT aromatic, NOT planar precursor of bile acids and sterol hormones
40
derived from cholesterol, act as biological detergents
bile salts
41
bile salts
stored in the gallbladder, released when lipids are metabolized break lipids up into smaller particles, making triglycerol compounds more accessible to lipase enzymes
42
common steroid hormones derived from cholesterol
progesterone, testosterone, estradiol
43
prostaglandins
lipids that are synthesized in complex pathways from arachidonic acid; have hormone-like functions for short time periods
44
NSAIDs block...
prostaglandins to reduce pain
45
how and why do phospholipids form vesicle bilayers and what are the characteristics of these bilayers?
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
vesicle bilayers function as
artificial cells and can transport molecules across mammalian membranes
47
micelle
no water inside, hydrophobic interior
48
vesicles
water-filled interior
49
the key component of fluid mosaic model
polyunsaturated fatty acids in membrane phospholipids
50
movement of fluid mosaic model protein molecules
fluidity allows them to diffuse laterally, but they *do not rotate*
51
features of fluid mosaic model
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
components of FMM
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
inner leaflet of FMM
tend to have phospholipids with net negative charge
54
outer leaflet of FMM
phospholipids tend to be neutral
55
FMM membrane asymmetry is for...
cell homeostasis
56
how do components of fluid membranes diffuse?
membrane proteins and lipids diffuse laterally in the plane of the membrane; do NOT rotate from one side to another
57
complex carbohydrates are found where on the membrane
extracellular face, attached to glycoproteins and proteoglycans
58
why are phospholipids distributed asymmetrically in the membrane and what is the consequence of this distribution?
inner leaflet is rich in phospholipid with net (-) charge outer leaflet has neutral phospholipids consequence = different charges
59
integral membrane proteins (location and removal)
immersed in nonpolar interior of the membrane with high % of nonpolar amino acids difficult to remove from the membrane, need detergents
60
peripheral proteins (location and removal)
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
in what ways is the protein glycophorin typical of integral membrane proteins?
has a series of hydrophobic amino acids that are immersed in the membrane with alpha-helical conformation
62
what part of the glycophorin protein are hydrophobic? which is hydrophilic?
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
what is a hydropathy plot, and what do such plots tell us about membrane proteins such as glycophorin?
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
what types of compounds can pass through a biological membrane using simple diffusion
small, non-polar molecules and gases ex: O2, CO2, N, urea, ethanol
65
simple diffusion
no energy or help needed diffusion from high to low concentration not saturated, not sensitive to inhibitors
66
facilitated diffusion
move through a protein tunnel, still with no energy needed sugars, amino acids, ions, nucleotides, and water diffuse this way
67
molecular characteristics of the integral membrane protein transport systems
calcium-ATPase transport calcium ions across mammalian membranes non-polar with lots of non-polar amino acids
68
active transport system
substrate moves through a tunnel with energy, low to high concentration
69
primary active transport
*directly coupled to ATP hydrolysis,* against a concentration gradient, direct coupling to an energy source saturable and sensitive to inhibitors
70
secondary active transport
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
SYMport
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
ANTIport
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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