Lipids lecture 1 Flashcards

1
Q

What is olestra?

A

“fat free fat”

a FA attached to a sugar

can’t be metabolized

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2
Q

chemical characterization of lipids?

A

insolubility of in water

soluble in non polar organic solvents

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3
Q

3 classes of lipids?

A
  1. simple
    2 compound
    3 derived
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4
Q

categories of simple lipids?

A

fats and waxes

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5
Q

types of compound lipids?

A

phospholipids
glycolipids
lipoproteins

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6
Q

what are simple lipids?

A

esters of FA connected to an alcohol

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7
Q

types of derived lipids?

A

fatty acids
fatty alcohols
hydrocarbons

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8
Q

what are fats (simple lipids)?

another name?

A

esters of FA connected to glycerol

R1 R2 R3 are FA (short to long chain aliphatic hydrocarbons with a COOH group at one end)

aka triacylglycerols/triglycerides

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9
Q

oil vs fat?

A

oil: low mp and liquid at room temp
fat: solid at room temp

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10
Q

percent of triglycerides in extractable lipid material in biological systems and in lipid that we consume?

A

> 90%

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11
Q

melting profile of pure triglyceride vs edible fat?

A

triacylglycerol has a very sharp melting point

edible fat melts over a wider range of temp because it is a mixture of different triacylglycerol molecules

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12
Q

chemical structure of waxes?

A

FA esterified with a simple fatty alcohol (other than glycerol)

aliphatic alcohol + FA = wax

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13
Q

what is a true wax

A

FA esterified to a SIMPLE fatty alcohol

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14
Q

uses of waxes?

sources of wax?

A
sealing agents (cheese)
polishing agents (apples)

sources: injojoba oil, beesewax

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15
Q

jojoba oil structure and use?

A

structure: linear esters of mono unsat long chain FA esterified to fatty alcohols
use: cosmetics. low cal ingredient (not digested readily)

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16
Q

structure of cholesterol?

A

FA esterified to a complex alcohol

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17
Q

what are compound lipids? types?

A

simple lipid conjugated to a non lipid

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18
Q

structure of phospholipids?

what is the base structure?

what are the different phosphatidic acid molecule examples?

A

triglycerides with one FA replaced with a nonlipid moiety - phosphoric acid

base structure = phosphatidic acid (when X=OH)

other phospholipids: X=nitrogenous base

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19
Q

classes of phospholipids

A
  1. lecithins (phosphatidyl cholines)
  2. Cephalins (phosphatidyl ethanolamines): phosphatidic acid conjugated to ethanolamine (x=OH-CH2-CH2-NH2)
  3. Phosphatidyl inositols: non nitrogenous group + phosphatidic acid
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20
Q

hydrophilicity of phospholipids?

how much is found in food systems?

A

contains both hydrophobic and hydrophillic groups

thus, good emulsifier (ie soybean oil )

in food systems: comprises <5% of lipid material

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21
Q

what are glycolipids and sphingo lipids?

structure?

examples of glycolipids in cell membranes?

A

in cell membrane lipids in plants and animals

complex structure: combination of glycerol backbone, FA, carb, nitrogenous group

ex in cell membranes: glycoproteins, glycolipid, glycocalix

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22
Q

role and structure of lipoproteins?

A

circulates in blood to carry lipids to tissues for metabolism or storage

HDL and LDL (different sizes and levels of protein, fat and cholesterol)

structure:
inside: triglyceride + cholesterol esters
outside: phospholipid + cholesterol + apolipoprotin

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23
Q

LDL vs HDL?

A

HDL: good. accounts for 1/3 of blood circulating cholesterol. protective to heart disease

LDL: excess = plaque in blood vessels = artery blockages

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24
Q

what are derived lipids?

A

derived from simple of compound lipid categories. Still retains hydrophobic character

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25
Q

types of derived lipids (3)

Role in food systems?

A
  1. fatty acids
  2. fatty alcohols
  3. hydrocarbons and oxygenated derivatives

role in food systems: major role in functionality

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26
Q

structure of fatty acids (as type of derived lipids)?

A

short to long chain aliphatic hydrocarbons w/ COOH group at one end

27
Q

what are short chain FA important for?

ex?

A

flavour compounds

can be released by lipolysis

ex: 
butyric acid (C3)
Caproic acid (c6)
caprylic acid (c8) --> rancid cheese flavor
28
Q

what can presence of FFA do?

A

lower the smoke point of edible oils when used for frying

29
Q

do long chain free fatty acids have flavour?

A

no

but can give soapy flavour in presence of mineral salts

30
Q

short chain alcohols are…

more complex derived alcohols are….

A
  1. major contributors to flavour

2. often biologically active (ie cholesterol)

31
Q

what are terpenes? what are they commonly known for?

A

built from isoprene units (isoprene = 5 carbons)

known for components of fragrant oils from leaves, flowers, fruits (ie. essential oils)

32
Q

terpene classes?

A

monoterpenes = 2 isoprene units = 10C

sesquiterpenes = 3 isoprene = 15 C

diterpenes = 4

sesterterpenes = 5

triterpenes = 6

33
Q

how are lipids surface active?

A

they are amphiphillic

34
Q

2 main lipid components in food systems?

A

fats from simple lipids

phospholipids from compound lipids

95% of lipid from biological systems is Fat (triglycerides) with mostly phospholipids

35
Q

what are key determinants of triglyceride properties?

A

the physical and chemical properties of the fatty acids attached to the glycerol

36
Q

what are the 2 types of triglycerides?

A

sat FA:

  • simple and least reactive
  • linear series of methyl groups terminating in a COOH group
  • CH3-(CH2)n-COOH

unsat FA: has one or more double bonds. most common are oleic, linoleic and linolenic

37
Q

are FA in nature even or odd numbered?

A

even

odd numbered can’t be packed into a crystalline lattice

38
Q

are short or long chain FA liquid or solid at room temp?

A

short chain (4-8 C): liquid at room temp

long chain (more than 10C): solids

39
Q

when chain length is increased in FA, how does water solubility change?

A

longer chain = increased hydrophobicity = decreased water solubility

as aresult, C4-C8 FA are slightly miscible with water (b/c of small chain = low hydrophobicity)

40
Q

describe surface tension properties of soap

A

soap = salt form of FA

water soluble but strong surface tension reducing properties

structure: has long FA chain and charged NA+ end

41
Q

2 systems of nomenclature?

A
  1. trivial names

2. systematic names (IUPAC)

42
Q

from where is the position of the double bond counted in the IUPAC system?

A

from the carboxyl end of the FA chain

43
Q

what is a side reaction of hydrogenation?

A

natural cis form to trans

affects properties of the molecule

44
Q

what are two forms to how DBs are situated relative to each other?

stability of both?

A
  1. unconjugated DB: separated by methylene group (CH2). The natural state of most FA
  2. conjugated DB: DB are right next to each other. not interrupted by CH2 group. Not usually found naturally, but commonly formed during oil processing.
    stability: conj form is more stable but more susceptible to autoxidation
45
Q

what are mixed bonding systems?

A

has both conjugated and unconj elements

thermodynamically preferred but very susceptible to autoxidation

responsible for reversion associated with soybean and fish oils

leads to formation of an active methylene group (CH2 positioned between a conj and unconj DB)

46
Q

what is an active methylene group?

A

it is positioned between conjugated and unconj double bonds

47
Q

what are assumptions made with the omega nomenclature?

A
  1. all natural FA are cis

2. all DB are unconjugated

48
Q

what end does the “omega carbon” count carbons from?

A

from the CH3 end

(review omega nomenclature on slides)

DB are always 3 carbons apart

49
Q

what is linoleic acid

A

omega 6 family

essential FA

needed for biologically active membranes

50
Q

what family is linolenic in?

A

omega 3 family

synthesized only by plants

essential FA

51
Q

what is CLA?

A

conjugated linoleic acids

found in meat and milk

has an anticarcinogenic effect

52
Q

molecular crumpling?

A

caused by increase in number if cis DB

53
Q

how is the crystalline lattice stabilized?

A
  1. hydrophobic interactions along acyl residues

2. more carbons in chain = energy and temp needed to melt crystal increases

54
Q

what type of DB influences arrangement of crystalline lattice the most?

A

influenced by cis DB, but trans DB

55
Q

what are branched chain FA? example?

A

has a hydrocarbon branch in the chain

ex: malvalic acid: in cottonseed oil. causes egg color problems in eggs

56
Q

what are hydroxy acids? ex?

A

contains a OH group in the FA chain. found in castor bean tree

ex: ricinoleic acid

57
Q

what are cyclic FA?

A

has a cyclic group in chain

58
Q

what are actylenic FA?

A

has a triple bond in chain

useful as antifungal

59
Q

what are 4 less common FA?

A

branched chain FA
hydroxy acids
cyclic FA
actylenic FA

60
Q

IUPAC of C18? C10? C16? (fatty acids)

A

C18: octadecanoic acid

C10: decanoic acid

C16: hexadecanoic acid

61
Q

IUPAC of C18:1? C18:2?

presence of a DB

A

C18:1 = octadecENOIC acid

C18:2 = octadecaDIENOIC acid

62
Q

IUPAC name for C18:1(9)? C18:2(9,12)? c18:3(9,12,15)?

A

C18:1(9) = octadeca-9-enoic acid

C18:2(9,12) = Octadeca-9,12-dienoic acid

c18:3(9,12,15) = Octadeca 9,12,15-trienoic acid

63
Q

why is there naturally some trans FA in butteR?

A

due to hydrogenation of cis FA by rumen microorganisms.

around 6% of total fat is trans

64
Q

what is positional isomerism?

A

many combinations based on position of DB on parent chain or whether it is cis or trans