Lipids - Summary Flashcards
1
Q
What are the three groups of lipids?
A
- Simple lipids
- Compound lipids
- Derived lipids
2
Q
What are the two groups of simple lipids?
A
- Triglycerides
- Waxes
3
Q
What are the three groups of compound lipids?
A
- Phospholipids
- Glycolipids
- Lipoproteins
4
Q
What is jojoba oil?
A
An ester (simple lipid)
5
Q
Why does an edible fat melt over a much wider range than a pure triglyceride?
A
Because it consists of many different pure TG molecules, each with different melting points
6
Q
What are waxes?
A
Esters of fatty acids esterified with an alcohol, other than glycerol
7
Q
Give examples of compounds in the wax category.
A
- Cholesterol
- Esters of vitamin A
8
Q
When X is OH, what is the phospholipid called?
A
Phosphatidic acid
9
Q
When X is O-CH2-CH(NH2)-COOH, what is the phospholipid called?
A
Phosphatidylserine
10
Q
When X is a sugar, what is the phospholipid called?
A
Phosphatidylinositol
11
Q
When X is O-CH2-CH2-N+(CH2)3, what is the phospholipid called?
A
Phosphatidylcholine (lecithin)
12
Q
When X is O-CH2-CH2-NH2, what is the phospholipid called?
A
Phosphatidylethanolamine (cephalin)
13
Q
What is the fundamental unit of terpenes? How many carbons does it contain?
A
Isoprenes (5 carbons)
14
Q
How many isoprene units and carbons do monoterpenes contain?
A
2 isoprene units, 10 carbons
15
Q
Name the terpene classes in chronological order.
A
- Monoterpenes
- Sesquiterpenes
- Diterpenes
- Sesterterpenes
- Triterpenes
16
Q
What chain length of fatty acids are slightly miscible with water?
A
C4-C8
17
Q
What is the systematic name of myristic acid?
A
Tetradecanoic acid (14:0)
18
Q
What is the systematic name of stearic acid?
A
Octadecanoic acid (18:0)
19
Q
What is the systematic name of palmitic acid?
A
Hexadecanoid acid (16:0)
20
Q
What are the names for 18:1, 18:2, and 18:3 fatty acids?
A
- Oleic
- Linoleic
- Linolenic
21
Q
Give the systematic names of fatty acids from C2 to C22 (even-numbers only).
A
- Ethanoic (C2)
- Butanoic (C4)
- Hexanoic (C6)
- Octanoic (C8)
- Decanoic (C10)
- Dodecanoic (C12)
- Tetradecanoic (C14)
- Hexadecanoic (C16)
- Octadecanoic (C18)
- Eicosannoic (C20)
22
Q
What are C2:0, C4:0, and C12:0 fatty acids?
A
- C2:0 - acetic
- C4:0 - butyric
- C12:0 - lauric
23
Q
How do you indicate the presence of a double bond in nomenclature?
A
By the suffix “enoic”
24
Q
What are unconjugated double bonds?
A
Separated by a methylene group (natural state)
25
What is a conjugated double bond?
Double bonds are next to each other (more susceptible to autoxidation)
26
Which fatty acid is readily converted to a mixed bonding system? What does that lead to?
- Linolenic acid
- Formation of an active methylene group, positioned between a conjugated and unconjugated double bonds
- Very susceptible to autoxidation
27
What is largely responsible for reversion in soybean and fish oils?
The active methylene group of linolenic acid
28
Where do you start counting in Omega-nomenclature? What does 10:23 mean?
- Methyl end
| - 10 carbons with two double bonds, the first positioned at 3 from the methyl end
29
What is 20:46?
Arachidonic acid
30
What are the distinguishing features of the milkfat group?
- High levels of long-chain saturated fatty acids
| - Unique and substantial portion of short-chain fatty acids (ex: butyric acid)
31
What is responsible for the "rancid like" odor from lipolysis in milkfats?
Short-chain fatty acids
32
What are sources of the lauric acid group?
- Palm kernal oil (extracted from oilseed)
- Coconut
- Tropical oils
33
What is palm oil?
- Extracted from palm FRUIT
| - Much more unsaturated, not a lauric acid
34
What is the distinguishing feature of the lauric acid group?
- High content of lauric acid (C12:0)
| - Mostly saturated
35
Why are lauric acids oils at room temperatures?
Despite their saturation, they are oils due to lauric acids short-chain (C12)
36
Which group is resistant to oxidative rancidity?
Lauric acid, due to their low degree of unsaturation
37
Give examples of the oleic-linoleic acid group.
- Cottonseed
- Olive
- Peanut
- Corn
38
Why don't oleic-linoleic group fatty acids suffer from reversion?
Negligible amount of linolenic fatty acids
39
Give examples of linolenic acids.
Soybean, hempseed
40
Which group's fatty acids are qualified as drying oils?
- Linolenic acids
| - Because of their ability to polymerize into a hard film if applied as a thin layer
41
Why are animal fat depot group fats rather than oils?
- Despite their high content of unsaturated fatty acids,
| - They are fats because they have a higher ratio of GS2 (disaturated) and GS3 (trisaturated) glycerides
42
What is the distinguishing feature of marine oils?
- High in long-chain unsaturated fatty acids (C16-C22)
- Very highly unsaturated (up to 6 double bonds)
- High in omega-3 fatty acids
- REVERSION and autoxidation
43
Give examples of erucic fatty acids.
- Rapeseed oil
| - Mustard oil
44
What is erucic acid?
- C22:1
| - Health hazard
45
What is canola oil?
Low erucic acid edible oil
46
Corn oil, safflower oil, and sunflower oil are examples of what?
Omega-6 fatty acids
47
Olive oil, avocados, peanuts, and almonds are examples of what?
Omega-9 fatty acids
48
What does lipase catalyze?
- Lipolysis
| - Hydrolysis of the ester linkage between glycerol and a fatty acid in a TG
49
What does lipoxygenase catalyze?
- The oxidation of polyunsaturated fatty acid chains that have a cis-cis-1,4-pentadiene group
50
What are the three ways to obtain oil from a plant source? How are they different?
- Hydraulic pressing: poor quality, long time, more enzyme damage
- Expelling: press cake still contains oil, followed by solvent
- Solvent extraction: organic solvent (hexane), efficient
51
What are the four steps to the refinement of oil?
1) Settling and degumming
2) Refining
3) Bleaching
4) Deodorization
52
What does settling and degumming extract? How?
- Mixing the oil with water and allowing it to stand
| - Carbohydrates, proteins, and phospholipids dissociate (aqueous)
53
What does refining extract? How?
- Treatment with dilute alkali, to convert FAs into soap
| - Removal of free fatty acids from the oil
54
What does bleaching extract? How?
- Oil is passed through dry bentonite or clay
| - Removal of coloured material from the oil
55
What does deodorization extract? How?
- Steam stripping
| - Removal of volatile compounds
56
What is biodiesel?
Methyl esters
57
How can fatty acid composition/distribution be determined?
Gas chromatography
58
What is winterization? What was it developed with?
- Cooling down the oil to remove saturates
| - Cottonseed oil
59
What are the functions of hydrogenation? (2)
- Convert an oil into a fat
| - Reduce the susceptibility of an oil to oxidative rancidity
60
What are the double bonds formed by hydrogenation capable of? What does that result in?
- Wandering (positional isomerism)
| - Conversion of unconjugated double bonds to mixed bonding systems
61
What is selectivity?
Hydrogenation prefers highly unsaturated fatty acids
62
Why is interesterification used in lard?
- GS2U component is made of oleopalmitostearin, which has a propensity to form large crystals
- Interesterification solves that problem
63
What are the two ways to determine the solid fat content?
- Dilatometry
| - Nuclear magnetic resonance (NMR)
64
What is plotted in a dilatometry graph?
Specific volume, inverse of density (y) as a function of temperature (x)
65
What do the three sigmoidal represent in dilatometry?
1) Thermal expansion of the solid fat
2) Expansion due to a change in state
3) Thermal expansion of the ilquid only
66
What is the equation of the solid fat index?
- (X/Y) x 100
- X is the measurement between the curve and the liquid line
- Y is the measurement between the liquid line and the solid line
67
Which polymorphic form has the highest and lowest melting point?
- Highest: beta
| - Lowest: alpha
68
What polymorphic form arises from the rapid cooling of liquid fat?
Alpha
69
What polymorphic form arises from the slow cooling of liquid fat?
Beta
70
Beta-Prime is the polymorphic transformation of what?
Alpha
71
Coconut, corn, and olive oil prefer the _____ crystal form
beta
72
Cottonseed, milk fat, and palm oil prefer the ______ crystal form
beta-prime
73
What are the four methods for conversion from beta to beta-prime?
- Interesterification
- Interesterification and hydrogenation
- Winterization
- Addition of cottonseed oil and/or tallow flakes
74
Differentiate interesterification and intraesterification.
- Interesterification: exchange among TG molecules
| - Intraesterification: exchange WITHIN a TG molecule
75
What are high temperature base catalysts for interesterification? What is the low-temperature catalyst?
- High: KOH and NaOH
| - Low: NaOCH3 (sodium methoxide)
76
What are the three steps to interesterification?
1) Formation of enolate ion
2) Formation of B-keto ester
3) Interesterification
77
What is the definition of catalyst activity?
Decrease in iodine number per unit of time during a hydrogenation under a specific set of conditions
78
What is the iodine number? What does it indicate?
- The number of grams of iodine absorbed by 100 grams of fat
| - Indicates the degree of unsaturation of the fatty acid
79
What are the independent variables affecting the reaction rate of hydrogenation?
- Nature of the substance
- Concentration of the catalyst
- Pressure
- Temperature
- Agitation
80
What are the dependant variables affecting the reaction rate of hydrogenation?
- trans fatty acids
- Selectivity ratio
- Hydrogenation rate
81
How does an increase in temperature affect the selectivity ratio, trans content, and reaction rate in hydrogenation?
Selectivity ratio: increases
Trans content: increases
Reaction rate: increases
82
How does an increase pressure affect the selectivity ratio, trans content, and reaction rate in hydrogenation?
Selectivity ratio: decreases
Trans content: decreases
Reaction rate: increases
83
How does an increase in agitation affect the selectivity ratio, trans content, and reaction rate in hydrogenation?
Selectivity ratio: decreases
Trans content: decreases
Reaction rate: increases
84
How does an increase in catalyst affect the selectivity ratio, trans content, and reaction rate in hydrogenation?
Selectivity ratio: increases
Trans content: increases
Reaction rate: increases
85
What is saponification?
Hydrolysis of an ester under alkaline conditions
86
How do you use gas chromatography?
1) Saponify
2) Chromatograph methyl esters
3) Determine peak areas
87
What are the two methods to obtain the iodine value?
- Wijis
| - Hanus
88
What is cocoa butter composed of?
- 80% is DISATURATED
| - SOS, POS, POP
89
What determines the characteristic cocoa butter texture?
POS
90
What happens when POS in cocoa butter is transformed from the beta-prime form to the beta form?
Chocolate "bloom" - white spots and dull surface appearance
91
What is tempering?
Process which permits transformation to the proper polymorphic form
92
What is reduced in the random interesterification of lard?
Proportion of palmitic acid in the 2-position is reduced --> improves its plastic range
93
What is autoxidation? What is the overall result?
- Reaction of unsaturated FAs with molecular oxygen
| - Development of rancidity
94
What does autoxidation require?
1) Hydrogen must be abstracted from the FA chain
| 2) Molecular oxygen must be present
95
How can hydrogen be abstracted from the FA chain?
- Light
- Heat
- Metallic cations
- Lipoxygenase
- Singlet oxygen
96
What is propagation in autoxidation?
Reaction of the fatty acid free radical with oxygen
97
What is the key to the self-propagating nature of the autoxidation reaction? What does that form?
- The peroxy radical has a preference for terminating its free radical state by abstracting a hydrogen from another FA
- Forms a hydroperoxide and a new FA radical
98
What are the primary oxidation products?
- Hydroperoxides (predominate)
| - Peroxides
99
What are the compounds responsible for off-flavors in autoxidation? What is their precursor?
- Low-molecular weight aldehydes, alcohols, ketones
| - Hydroperoxide
100
When does the monomolecular hydroperoxide mechanism predominate?
When the hydroperoxide concentration is low
101
When does the bimolecular hydroperoxide mechanism predominate?
When the hydroperoxide concentration is high
102
What does the monomolecular reaction form?
Alkoxy and hydroxy radicals
103
What three reactions can an alkoxy radical undergo? Which releases a free radical?
- Aldehyde generation (radical)
- Alcohol generation (radical)
- Ketone generation (termination)
104
What reactions can an aldehyde undergo? (2)
- Oxidation to a carboxylic acid
| - Reduction to an alcohol
105
What does the bimolecular reaction form?
Alkoxy and peroxy radicals + H2O
106
What do peroxy radicals prefer to do?
Abstract a hydrogen from a fatty acid
107
What do alkoxy radicals prefer to do?
Decompose --> aldehydes, ketones, alcohols, carboxylic acids
108
What does the peroxide value indicate? Does it accurately portray rancidity?
- Measures the quantity of hydroperoxides
| - No, since hydroperoxides decrease at the end of the reaction since they are degraded, which produces the off-flavours
109
What is the slow accumulation of hydroperoxides called?
Induction period (primarily monomolecular reaction)
110
What does the TBA test indicate?
- Secondary breakdown products of autoxidation
| - MALONALDEHYDE --> produces a red complex
111
Is citric acid an antioxidant? Why/why not?
- No, it is a chelating agent (synergistic agent)
| - It does NOT interfere with primary autoxidation mechanism
112
What are metal ions contribution to autoxidation?
Allow for the formation of more reactive singlet oxygen, which can attack lipids directly
113
Give examples of synergists.
- Ascorbic acid
| - EDTA
114
What are the detrimental effects of lipoxygenase?
1) Destruction of essential FAs
2) Free radicals produce damage
3) Development of off-flavour
115
Give examples of preventative antioxidants.
- Superoxide dismutase
- Catalse
- Glutathione peroxidase
- EDTA
116
Give examples of radical scavenging antioxidants.
- Vitamin C
- Tocopherol
- Anthocyanin
117
Does a hydroxy free radical have a low or high electron reduction potential?
- High (2300)
| - Greater affinity for electrons, will get reduced
118
What should antoxidants not exceed?
200 ppm
119
What is an ideal antioxidant?
- No harmful physiological effects
- Effective in low concentration
- Readily-available
- Economical
- Fat-soluble
