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Food Chemistry 1 > 1. Types of lipids + FA > Flashcards

1. Types of lipids + FA Flashcards

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1
Q

Lipids are characterized by their _______ sensation and ___________ properties when isolated

A

fatty sensation and lubricant properties

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2
Q

solubility of lipids vs insolubility of lipids

A
  • soluble in nonpolar organic solvents (hexane, chloroform, ether)
  • insoluble in water
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3
Q

3 major classes of lipids + what?

A
  1. simple lipids: FA esterified to alcohol
  2. compound lipids: conjugated to non-lipid moiety
  3. derived lipids: derived in living systems from simple or compound lipids
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4
Q

structure of glycerol

A

3 carbon chain with OH on each carbon + H to fill all 4 of carbon’s bonds

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5
Q

Triacylglyceride structure + type of bond?

A

3 FA esterified to glycerol
- ester linkage

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6
Q

Are the R groups of FA in triacylglycerol the same?

A

no. short of long chain with carboxyl group at one end

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7
Q

triglycerides account for ___% of extractable lipid material present in biological systems

A

90%

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8
Q

difference between oil and fat?

A
  • oil: liquid at room temp
  • fat: solid at room temp
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9
Q

Melting point: pure TG vs fats/lipids

A
  • pure TG: sharp melting point
  • fats: solid fat content decreases over a broad temperature range –> reflects mixture of TG
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10
Q

short or long FA chain will melt faster?

A

short chain

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11
Q

what are waxes?

A

FA esterified to a fatty alcohol (long chain alcohol)

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12
Q

example of liquid and solid wax

A
  • liquid: jojoba oil
  • solid: beeswax
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13
Q

Biosynthesis of wax: 2 steps + enzymes

A
  1. FA bound to Coenzyme A –> FA reductase catalyzes reduction of FA to fatty alcohol (carboxylic acid to alcohol)
  2. Fatty alcohol + FA bound to CoA (different than first one) –> Wax synthase –> makes wax ester
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14
Q

waxes have limited application for food use –> 2 examples

A
  • sealing agents (cheese)
  • polishing agents (apples)
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15
Q

Jojoba oil –> what? found where? used in what? + also considered as a potential _________ (because not __________ readily) food ingredient giving a __________

A
  • liquid wax
  • obtained from seeds of desert shrub native to southwestern US and norther Mexico
  • cosmetics
  • low calorie (bc not digested readily)
  • fatty sensation
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16
Q

True wax vs other compounds in wax category (examples)

A

true wax: FA esterified to a simple fatty alcohol
- other wax category: FA esterified to complex alcohols –> cholesterol and retinol

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17
Q

Cholesterol and retinol –> present in what degree of quantity?
+ important bc they are ?

A
  • mg and micrograms
  • bc they are biologically active
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18
Q

Cholesterol structure? vs cholesteryl ester (wax)

A

OH + 4 rings ish + alkyl chain
vs wax: R-C(double bond O)-O-4 rings ish + alkyl chain

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19
Q

retinol structure? vs vitamin A ester (wax) structure

A

Retinol: hexane ish + alkyl chain with conjugated double bonds + OH
wax: hexane ish + alkyl chain + CH2O-C(double bond O)-R

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20
Q

what are compound lipids?

A

A category of lipids made up of a simple lipid (generally TG) conjugated to a non-lipid molecule

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21
Q

Compound lipids usually separated into 3 categories:

A
  1. Phospholipids
  2. Glycolipids/sphingolipids
  3. Lipoproteins
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22
Q

What are phospholipids?

A

TG with one of FA replaced with phosphoric acid or phosphoric acid derivative

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23
Q

When the non-lipid moiety is a phosphoric acid instead, the phospholipid is called ?
Structure?

A

phosphatidic acid
Glycerol + 2 FA + O-P(double bonded O)(-O minus)-OH

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24
Q

Structure of
- phosphatidylethanolamine
- phosphatidylcholine
- phosphatidylserine
- phosphatidylinositol

A

Glycerol + 2 FA + O-P(double bonded O)(-O minus)-X
- ethanolamine: X = O-CH2-CH2-NH2
- choline: X = O-CH2-CH2-N+(CH2)3 –> emulsifier!
- serine: X = O-CH2-CH(NH2)-COOH
- inositol: hexane with OH on each carbone

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25
Q

Which type of phospholipid is lecithin? cephalin?

A
  • lecithin: Phosphatidylcholine
  • cephalin: ethanolamine
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26
Q

What is particular of phosphatidylinositols? (3)

A
  • non-nitrogenous groups attached to phosphatidic acid
  • cell membrane
  • not useful for food commodity
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27
Q

Phospholipids comprise ____% of lipid material found in food systems

A

<5%

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28
Q

Phospholipids have excellent _____A____ properties bc have both ________ and _______ groups
- common source of commercial A?

A

A: emulsifying
- hydrophobic and hydrophilic
- soybean oil

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29
Q

Glyco and sphingolipids are associated with _________________ in both plants and animals

A

membrane lipids

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30
Q

Glyco and sphingolipids = important class of lipids for food scientist?

A

No! although very important biochemically

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31
Q

Which type of lipids have a structure that is rarely known?

A

protein-lipid complexes (lipoproteins)

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32
Q

Function of lipoproteins?

A

circulate in blood to carry lipids to tissues for metabolism or storage (+ vice versa)

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33
Q

2 types of lipoproteins? + important in relation to which disease?

A
  • High density lipoproteins and low density lipoprotein
  • heart disease
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34
Q

Lipoproteins typically found in high levels in what food?

A

eggs

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35
Q

HDL vs LDL:
- good or bad?
- accounts for what fraction of all blood circulating cholesterol
- function
- higher levels = ?

A

HDL:
- good
- 1/3
- protective mechanism from dev. of heart disease by carrying away cholesterol from vessel walls and plaque to liver for disposal
- reduce risk of heart attack
LDL:
- bad
- N/A
- transports substances vital to cell function and development
- can accumulate in blood vessel walls –> blocks arteries + unstable plaque build-up = prone to rupture and formation of blood clots –> levels of LDL related to risk of heart attack and stroke

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36
Q

what are derived lipids?
+ 3 examples

A
  • constituents derived from simple or compound lipid categories and that still retain their hydrophobic character
  • FA, fatty alcohols, hydrocarbons and oxygenated derivatives thereof
37
Q

Are derived lipids found in food systems?

A

Yes! and can play major roles in terms of functionality

38
Q

Describe derived lipids fatty acids

A

Short to long chain aliphatic hydrocarbons with carboxyl group at one end

39
Q

short chain FA (important as ________ compounds (______ or _____) + released by ________ + examples) vs longer-chain free fatty acid (flavour? + > C ___?)
- hint: give flavour? why or why not? at low of high concentration?

A

Short chain:
- important as flavour compounds
- can be released by lipolysis and can contribute to good (low concentration) or bad flavour (high concentration)
- ex.: butyric acid (C4), caproic acid (C6), caprylic acid (C8) (cheese/rancid flavour)
Longer chain:
- no flavour per se (bc no receptors on tongue) but gives soapy flavour in presence of mineral salts
- > C12

40
Q

Presence of FFA can _______ the smoke point of edible oils when used for ________

A

lower, frying

41
Q

Fatty alcohols made of (2)
- short or long chain = major contributor to flavour?
- more complex derived alcohols are often _____________ (ex.: ?)

A

higher alcohols (>C6) and sterols CH3-(CH2)n-CH2-OH
- short
- biologically active –> cholesterol

42
Q

Examples of hydrocarbons and oxygenated derivatives thereof (4)

A
  • short and long chain aliphatic hydrocarbons
  • carotenoids
  • xanthophylls
  • terpenes
43
Q

straight chain saturated hydrocarbons vs diverse unsaturated hydrocarbons
- in terms of flavour/reaction

A
  • straight-chain –> of little note from flavour or reaction viewpoint
  • diverse –> more of interest –> specifically terpenes build from isoprene units
44
Q

How many carbons in isoprene units?

A

5 carbon

45
Q

Terpenes build from what units?
- found in what? what properties?
- what are main constituents of essential oils? (2 types of terpenes)

A
  • isoprene units
  • found in fragrant oils obtained from leaves, flowers and fruits –> antimicrobial properties
  • monoterpenes and sesquiterpenes
46
Q

Number of isoprene units?
- Monoterpene
- sesquiterpenes
- diterpenes
- sesterterpenes
- triterpenes

A
  • Monoterpene: 2
  • sesquiterpenes: 3
  • diterpenes: 4
  • sesterterpenes: 5
  • triterpenes: 6
47
Q

_________ is the analytical property used as the basis for lipids’ facile separation from _________ and carbs

A
  • water insolubility
  • proteins and carbs
48
Q

primarily ________ are deposited in some animal tissues and organs of some plants

A

Triglycerides

49
Q

lipid content in storage tissues can rise to ____-____% or higher
- what natural source has higher? how much?

A

15-20%
- soybean–> 40% lipid

50
Q

nutritive and physiological important of lipids based on (2)

A
  • role as fuel molecules (9kcal/g or 37 kJ/g for TG)
  • source of essential fatty acids and vitamins
51
Q

Lipid properties that are indispensable in food handling: pleasant _______ or _______ mouthfeel and ability to ________ many taste and aroma constituents of food

A
  • oily or creamy
  • solubilize
52
Q

Bulk of lipid components in food systems are (2) + % of each

A
  • fats and oils from simple lipid class –> 95-96%
  • phospholipid from compound lipid class –> 4-5%
53
Q

The composition and distribution of the (__________) _____ ____ on the ___________ backbone are major contributor to the overall properties of fats and oils extracted from biological systems

A

esterified fatty acid makeup + glycerol backbone

54
Q

Are fatty acids generally found in their free form in living biological systems?

A

no! they are largely combined in the form of TG

55
Q

How to make TG? in the lab (reaction formula)

A

1 glycerol + 3 FA + sodium hydroxide (catalyst) –> TG + 3 H2O

56
Q

When counting carbons for a FA attached to the glycerol, which C is the first one?

A

the carbon double bonded to an oxygen

57
Q

Saturated FA found in nature tend to be ______-numbered due to the mechanism of __________
vs sat FA with ______-numbered carbon –> found in very ____ amounts –> 2 examples

A

even-numbered
biosynthesis
- odd-numbered
- low
- pentadecanoic acid (15C) in milk –> around 1% of milk fat)
- heptadecanoic acid (17C) –> also in milk and plant oils –> around 0.6% of fat

58
Q

are short or long chained saturated FA liquid vs solid at room temp?

A

short = liquid
long = solid

59
Q

why does solubility of FA in water decrease with increasing chain length?

A

because increase of hydrophobicity

60
Q

______ form of FA (_____) is water soluble and has strong surface tension-reducing properties

A

salt form of FA (soap)

61
Q

how many carbons? + Systematic name
butyric acid
palmitic acid
stearic acid

A

butyric acid: C4: butanoic acid
palmitic acid: C16: hexadecanoic acid
stearic acid: C18: octadecanoic acid

62
Q

how many carbons? + Systematic name
caproic acid
lauric acid
arachidic acid

A

caproid acid C6: hexanoic acid
lauric acid: C12: dodecanoic acid
arachidic acid: C20: eicosanoic acid

63
Q

how many carbons? + Systematic name
- myristic acid
- capric acid
- caprylic acid

A
  • myristic acid: C14: tetradecanoic acid
  • capric acid: C10: decanoic acid
  • caprylic acid: C8: octanoic acid
64
Q

increase number of carbon = _______ melting point –> linear?

A

increase
- not linear!

65
Q

unsaturated FA have ______ melting points than sat. counterpart at same chain length

A

lower melting points

66
Q

Unsat FA are more or less reactive than sat? Why/what?

A

more reactive!
pentadiene system are highly reactive! –> where oxidation begins

67
Q

3 most common unsaturated fatty acids? which are more common than the other one?

A
  • oleic acid –> 18:1 (9) –> 34%
  • linoleic acid –> 18:2 (9,12) –> 34%
  • linolenic acid –> 18:3 (9, 12, 15) –> 5%
68
Q

oleic acid vs elaidic acid

A
  • both 18 carbon + 1 double bond
  • oleic: cis
  • elaidic: trans
69
Q

Cis or trans has lower melting point?

A

cis has lower melting point –> packs less tightly
vs trans (margarine): high melting point

70
Q

conversion of cis to trans has major effect on ______________ + on its _________ in the human body

A

melting point + metabolism in human body

71
Q

what can also affect physical properties of monounsat fat besides cis/trans configuration?

A

positional isomerism

72
Q

systematic name for C18:3 (9,12,15)

A

octadeca 9,12,15-trienoic acid

73
Q

IUPAC naming vs biochemical nomenclature –> start counting double bonds from which end?

A
  • IUPAC: from carboxylic end
  • biochemical: from CH3 end (omega carbon)
74
Q

omega nomenclature based on the assumption that all natural FA are in _____ form and double bonds are always ___________

A

cis form
unconjugated

75
Q

C(??): (?) + omega (?)
- eicosapentaenoic acid
- docosahexaenoic acid
- arachidonic acid

A
  • eicosapentaenoic acid–> C20:5 omega-3
  • docosahexaenoic acid –> C22:6 omega 3
  • arachidonic acid –> C20:4 omega 6
76
Q

3 family groups exist for omega families? what type?
- with exceptions: these are part of which families:
- erucic acid (20:1) in mustard family of seeds
- arachidonic acid (20:4)
- C20-C22 FA with 5-6 double bonds in fish lipids

A
  • omega 3 (linolenic type)
  • omega 6 (linoleic type)
  • omega 9 (oleic type)
  • erucic acid –> omega 9
  • arachidonic acid –> omega 6
  • C20-C22 FA with 5-6 double bond –> omega 3
77
Q

Natural state of most FA = __________ double bonds (separated by a __________ group)

A

unconjugated
- by a methylene group

78
Q

thermodynamically speaking, is conjugated or unconjugated form more stable? which is more susceptible to autoxidation?

A
  • conjugated form more stable
  • conjugated is more susceptible to autoxidation
79
Q

linolenic acid = relatively reactive and unstable and is readily converted into a __________ (what?)

A
  • mixed bonding system
  • having conjugated/unconjugated elements
80
Q

Formation of active methylene group –> positioned where?

A

between conjugated and unconjugated double bonds

81
Q

Conjugated linoleic acid (CLA) found in (2) are of special interest bc attributed to have an _______ effect
- most common = cis__ and trans__ isomer

A
  • found in milk and meat
  • anticarcinogenic effect
  • cis9 and trans11
82
Q

Why does 18:1 (2) and 18:1 (9) have such different melting points (51°C vs 13.4°C respectively)?

A

because the degree of the bend form by the double bond will modify the melting point!
- bigger the bend/angle, smaller the melting point will be

83
Q

Crystalline lattice of FA stabilized by (?) along the acyl residues

A

hydrophobic interactions

84
Q

Which FA can’t be packed into crystalline lattice?

A
  • unsaturated
  • odd-numbered
85
Q

Melting point of FA decreases with an increasing number of ____________ ___-double bonds

A

isolated cis-double bonds

86
Q

4 types of less common FA

A
  • branched chain FA –> have a hydrocarbon branch in the chain
  • Hydroxy acids –> contain hydroxyl group in FA, present in oil of castor bean trees
  • Cyclic FA –> contain a cyclic group in chain
  • Acetylenic FA –> contain triple bond –> useful as antifungal
87
Q

Malvalic acid = rare FA –> which category of less common FA?
- found in what?
- contains what?
- causes what? (2)

A
  • branched chain FA
  • found in cottonseed oil (1-3%)
  • contains cyclopropene ring
  • causes egg color problem in chicken eggs + pasty and rubbery yolks
88
Q

Ricinoleic acid –> which category of less common FA?
- makes about ___% of FA in _______ oil
- can serve as an indicator for presence of this oil in ________ oil
- very ________ side chain = useful in industrial processes

A
  • hydroxy FA
  • 80% in castor oil
  • edible oil
  • very reactive side chain

Food Chemistry 1 (22 decks)

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