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BIOL 3421 - molecular biochem > Lipid biochemistry: structural lipids > Flashcards

Lipid biochemistry: structural lipids Flashcards

1
Q

list some of the diverse functions of lipids (9)

A

energy storage, cell membrane components, enzyme cofactors, protein folding chaperones, electron carriers, light absorbing pigments, hormones, membrane anchors for proteins, intracellular messengers

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2
Q

list 6 categories of lipids based on the chemical structure

A

fatty acids
glycerolipids
glycerophospholipids
sphingolipids
sterols
prenols

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3
Q

what are fats and oils derivatives of

A

fatty acids

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4
Q

describe the basic structure of a fat

A

carboxylic acid joined to a hydrocarbon chain

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5
Q

how long is the hydrocarbon chain of a fatty acid (give a range)

A

4-36

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6
Q

T or F: fatty acids are highly reduced

A

true

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7
Q

what does it mean for a fatty acid to be highly reduced

A

they have lots of stored energy. they have lots of electrons that we are able to strip off

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8
Q

describe the variation that the hydrocarbon chain of a fatty acid can have

A

can be long or short, branched or unbranched, saturated or unsaturated

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9
Q

why do fats and oils make great energy storage molecules

A

the cellular oxidation of fatty acids into co2 and h2o is very exergonic (big energy release)

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10
Q

what is a cis double bond

A

adjacent groups on the same side of the double bond

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11
Q

what is a trans double bond

A

adjacent groups on different sides of the double bond

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12
Q

what is a mono-unsat fatty acid

A

one with one double bond

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13
Q

what is a poly-unsat fatty acid

A

one with two or more double bonds

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14
Q

describe the shorthand way of naming fatty acids

A

length of carbon chain : number of double bonds (Δ^position of double bond)

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15
Q

in naming fatty acids, 10 carbons =

A

deca

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16
Q

in naming fatty acids, 12 carbons =

A

dodeca

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17
Q

in naming fatty acids, 14 carbons =

A

tetradeca

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18
Q

in naming fatty acids, 16 carbons =

A

hexadeca

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19
Q

in naming fatty acids, 18 carbons =

A

octadeca

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20
Q

in naming fatty acids, 20 carbons =

A

eicosa

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21
Q

in naming fatty acids, 22 carbons =

A

docosa

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22
Q

in naming fatty acids, 24 carbons =

A

tetracosa

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23
Q

T or F: fatty acids usually have an odd number of carbons

A

false; they have an even number of carbons

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24
Q

T or F: unless specified, assume naturally occurring fatty acids are in the cis conformation

A

true

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25
Q

describe the systematic naming system of fatty acids

A

count the number of carbons and get the corresponding name, count the number of double bonds and get the corresponding name, and then determine the conformation and position of the double bonds

cis/trans - double bond position - systematic name

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26
Q

how are omega fatty acids named

A

they’re named in the reverse direction (starting at the methyl/omega end of the molecule)

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27
Q

describe the structure of omega 3 fatty acids

A

double bond at the 3rd to last carbon (from methyl end: C3=C4)

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28
Q

describe the structure of omega 6 fatty acids

A

double bond at the 6th to last carbon (from methyl end: C6=C7)

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29
Q

T or F: humans can synthesize omegas from enzymes

A

false; we cannot synthesize them, so they must be acquired from the diet

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30
Q

explain why omegas are considered essential

A

we must get them from the diet because we cannot synthesize them

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31
Q

explain why we need essential fatty acids (3)

A
  • they’re integral parts of cell membranes and affect function of membrane receptors
  • they’re parts of hormones that regulate blood clotting, contraction and relaxation of artery walls, and inflammation
  • they’re highly concentrated in retinal membranes and in grey matter membranes
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32
Q

list 4 things that deficiencies in essential fatty acids can result in

A
  • decreased growth in infants
  • poor wound healing
  • poor neuron growth, synapse formation, synaptic plasticity
  • vision problems
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33
Q

why can’t humans synthesize essential fatty acids?

A

humans lack the enzymes required to put double bonds near the methyl end of the molecule

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34
Q

in nature, how many carbons do FAs have

A

12-24

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35
Q

in nature, are FAs branched or unbranched

A

unbranched

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36
Q

in nature, what conformation are FA double bonds

A

cis

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37
Q

in nature, what is the location of a MUFA double bond

A

Δ9

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38
Q

in nature, what are the locations of the PUFA double bonds

A

Δ9,12,15

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39
Q

what is conjugation

A

when the bonds alternate between single and double

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40
Q

T or F: in nature, PUFAs are almost never conjugated

A

true

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41
Q

describe the solubility of fats in water

A

low but not zero

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42
Q

why is the solubility of fatty acids low but not zero

A

the carboxyl group is soluble but the rest isnt

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43
Q

would increasing the length of the FA chain increase or decrease its solubility in water? why?

A

decrease because less of the molecule would be soluble

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44
Q

would increasing the number of double bonds in the FA increase or decrease its solubility in water

A

increase

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45
Q

what is the consistency of saturated FAs at room temp

A

waxy (solid)

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46
Q

what is the consistency of unsaturated FAs at room temp

A

oily (liquid)

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47
Q

describe van der waals forces

A

electrons in an orbital are distributed asymmetrically and give a small charge to the atom. If atoms are precisely positioned apart, these small transitory charges can attract one another

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48
Q

when is a saturated fatty acid the most stable? why?

A

when it’s fully extended, because this minimizes steric hindrance

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49
Q

describe the behavior of extended sat fatty acids in regards to van der waals forces

A

extended sat FAs pack tightly together, close enough to maximize van der waals interactions. More VDW interactions = more thermal energy required to disrupt the FAs and a higher melting point

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50
Q

more VDW forces = more or less energy needed to disrupt the FAs?

A

more

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51
Q

more VDW forces = higher or lower melting point?

A

higher

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52
Q

describe VDW forces in regards to unsat FAs

A

unsat FAs have kinks that prevent tight packing = less VDW forces = less thermal energy required to disrupt the FAs = lower melting point

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53
Q

describe how rancidity occurs

A

when you leave foods out, oxidative cleavage of unsat FAs occurs at the double bond

54
Q

what is hydrogenation

A

turns natural cis unsat FAs into sat FAs (removes double bonds)

55
Q

the downside of hydrogenation?

A

partial hydrogenation can also create trans double bonds = trans fats

56
Q

describe the results of consuming trans fats

A

increase cardiovascular issues, raise bad blood cholesterol and lower good blood cholesterol, increase inflammation

57
Q

what are waxes?

A

esters of long chain FAs with long chain alcohols

58
Q

how long are the fatty acid chains in waxes?

A

14-36C

59
Q

is the melting point of waxes high or low

A

high

60
Q

is the solubility of waxes high or low

A

low

61
Q

describe some of the diverse functions of waxes

A
  • used by plankton as main energy source instead of TAGs
  • birds secrete waxes from skin glands to keep feathers water repellent
  • plants secrete waxy cuticle around leaves to prevent water loss
  • worker bees secrete wax to help make the honeycomb
  • used in lotions, polishes, shampoos, etc
62
Q

another name for triacylglycerols?

A

triglycerides (TAGs)

63
Q

how many FA chains do TAGs have

A

3

64
Q

what type of bond links the FA to glycerol in a TAG

A

ester

65
Q

describe the polarity of TAGs

A

almost entirely non polar, as the polar OH group of glycerol is bound in an ester linkage

66
Q

would a TAG be more or less soluble than a free FA

A

less soluble due to the carboxyl groups in ester bonds

67
Q

describe the composition of TAGs in adipocytes

A

TAG fat droplets fill almost the entire cell, causing the nucleus to be pressed against the PM

68
Q

function of adipocytes?

A

serve as reservoirs for metabolic fuel

69
Q

why is it beneficial to have TAG storage under the skin

A

helps insulate hibernating animals or animals in cold climates

70
Q

describe TAG storage in plants

A

TAGs are stored as oils in the seed, which provides energy + metabolic precursors during germination

71
Q

T or F: both TAGs and glycogen can serve as stored energy

A

true

72
Q

is energy storage mostly in TAGs or glycogen?

A

TAGs

73
Q

why is energy storage mostly in TAGs (3)

A
  • there is limited space for glycogen storage in the liver and muscles. TAG storage is much more available
  • TAGs are not hydrated, so it doesn’t come with water weight
  • TAGs store more J/gram of energy (they’re more heavily reduced)
74
Q

T or F: lipids are asymmetrically distributed across the two leaflets of the bilayer

A

true

75
Q

T or F: all structural lipids are membrane lipids

A

false; TAGs are not membrane lipids, they are storage lipids

76
Q

list the 5 membrane lipids

A

glycerophospholipids, sphingolipids, galactolipids, archaeal ether lipids, sterols

77
Q

backbone for glycerophospholipids?

A

glycerol

78
Q

what is the glycerol bound to in glycerophospholipids?

A

2 FAs and a head group

79
Q

what type of linkages link the FAs to glycerol in glycerophospholipids

A

ester

80
Q

what type of linkages link the head group to glycerol in glycerophospholipids

A

phosphodiester

81
Q

are the head groups of glycerophospholipids polar or non polar

A

polar

82
Q

T or F: in glycerophospholipids, one FA can sometimes be attached to the glycerol via an ether linkage

A

true

83
Q

when would we see a glycerophospholipid FA attached to the glycerol via an ether linkage

A

in hearts of vertebrates

84
Q

where are galactolipids located (which organism + which part of that organism)

A

thylakoid membranes in chloroplasts (in plants)

85
Q

T or F: galactolipids have phosphate

A

false; they’re phosphate free

86
Q

why is it important that galactolipids are phosphate free

A

phosphate can be limiting in the soil, so plants using galactolipids allows them to conserve their phosphate

87
Q

describe the structure of galactolipids

A

can use 1 or 2 galactose residues as a head group, and there are 2 FA chains

88
Q

galactolipids can make up __% of the total membrane lipids in plants

A

80%

89
Q

how do archaeal membranes survive such extreme environments

A

extra long hydrocarbon chains and they use ether linkages (which are more stable than esters at higher temps)

90
Q

describe the structure of archaeal ether-linked lipids

A

lipids are long and have branched hydrocarbon chains. They’re 2x the length of regular glycerophospholipids, and they span the entire length of the bilayer. CH chains are ether linked to glycerol on BOTH ends, and each glycerol has a head group attached

91
Q

what is the backbone for sphingolipids

A

sphingosine, not glycerol

92
Q

what type of groups does sphingosine have

A

amino and alcohol groups

93
Q

how many carbons are in the sphingosine backbone

A

18

94
Q

describe the structure of a sphingolipid

A

the long hydrocarbon chain of sphingosine is analogous to one fatty acid. Only one FA will bind to sphingosine via an amide linkage. The final glycerol-analogous carbon attached to a head group

95
Q

what does sphingomyelin contain in its head group

A

phosphate

96
Q

T or F: sphingomyelin is both a sphingolipid and a phospholipid

A

true; sphingosine backbone and the head group contains phosphate

97
Q

where is sphingomyelin found

A

myelin sheath of neurons

98
Q

what is the net charge of sphingomyelin

A

no net charge

99
Q

what type of head groups do glycosphingolipids have

A

sugar

100
Q

what is a cerebroside

A

a glycosphingolipid with a single sugar head group and no net charge

101
Q

what is a globoside

A

a glycosphingolipid with a multi sugar head group and no net charge

102
Q

what is a ganglioside

A

a glycosphingolipid with a multi sugar head group and at least one sialic acid sugar to provide a negative charge at pH 7

103
Q

what gives a ganglioside its negative charge

A

a sialic acid sugar

104
Q

where are gangliosides located in the body

A

on the surface of RBCs

105
Q

what do the gangliosides on the surface of RBCs determine

A

blood type

106
Q

T or F: all blood types have the same base

A

true

107
Q

how many sugars comprise the base of every blood type

A

5

108
Q

describe the structure of blood type O

A

just the base (5 sugars)

109
Q

describe the structure of blood type A

A

extra acetylgalactosamine

110
Q

describe the structure of blood type B

A

extra galactose

111
Q

what will happen when you receive blood with a different sugar head group

A

it will be recognized as foreign and be attacked by the immune system

112
Q

which bonds in glycerophospholipids are hydrolysable?

A

esters and phosphodiesters

113
Q

which enzymes hydrolyze esters and phosphodiesters in glycerophospholipids

A

phospholipases

114
Q

what does phospholipase A do

A

breaks ester bonds = releases one fatty acid from the glycerophospholipid

115
Q

what do phospholipase C and D do

A

break phosphodiester bonds in the head group

116
Q

how is Tay-Sachs disease caused

A

caused by a malfunctioning enzyme that can no longer cleave a ganglioside called GM2. = lipid accumulation

117
Q

describe what happens when GM2 cannot be cleaved (during Tay-Sachs disease)

A

it’s found int he nervous system, so the inability to degrade it will affect neuron function

GM2 deposits will accumulate in lysosomes –> loss of motor skills, muscle weakness, growth in head size, lack of response to surroundings (shows at 3-6 months of age)

blindness, paralysis, death by 3-4 years old

118
Q

how many rings do sterols have

A

4

119
Q

describe the structure of the rings in a sterol molecule

A

there are three 6C rings and one 5C ring. The rings are fused together. The molecule is very rigid and planar, with little rotation around C-C bonds

120
Q

what sterols do animals have

A

cholesterol

121
Q

what sterols do plants have

A

stigmasterol

122
Q

what sterols do fungi have

A

ergosterol

123
Q

what sterols do bacteria have

A

none! they can’t synthesize it

124
Q

how do sterols affect saturated fatty acids

A

they improve fluidity and prevent freezing, as sat FAs pack tightly together

125
Q

how do sterols affect unsaturated fatty acids

A

they compact and constrain movement = prevent melting, as unsat FAs do not pack tightly

126
Q

how are membrane rafts promoted

A

via sterols

127
Q

what is a membrane raft

A

microdomains of the PM that are thicker than the rest, and they’re enriched in cholesterol and glycosphingolipids

128
Q

list 5 characteristics of membrane rafts

A

more cholesterol, more glycosphingolipids, longer acyl chains, saturated acyl chains, more lipid-anchored proteins

129
Q

are membrane rafts common or uncommon? explain

A

common; they can cover up to half the membrane

130
Q

how many lipids does a membrane raft usually have? how many proteins?

A

a couple of thousand lipids + 10-50 proteins

131
Q

are proteins clustered or spread out in membrane rafts?

A

clustered

132
Q

what is the benefit to clusters of proteins within membrane rafts?

A

proteins are more likely to interact if they’re isolated on the same raft

BIOL 3421 - molecular biochem (20 decks)

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