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NUTR 301 > Lipids 1: Lipids Properties and Classes > Flashcards

Lipids 1: Lipids Properties and Classes Flashcards

1
Q

Biological functions of lipids

A
  • energy source and storage
  • major component of cell membranes
  • insulation
  • precursors to hormones and eicosanoids
  • Others: biological detergent, membrane anchors for proteins, receptors
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2
Q

How do lipids serve as barriers?

A

Not water soluble but the rest of the body is aqueous hence like a barrier

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3
Q

Chemical classification of lipids

A
  • fatty acids
  • glycerolipids
  • glycerophospholipids
  • steroids
  • eicosanoids
  • wax
  • sphingolipids
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4
Q

Another term for FFAs

A

Free fatty acids → non-esterified fatty acids

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5
Q

Structure of FFAs

A
  • Head: carboxylic acid
  • Tail: hydrocarbon chain
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6
Q

How are most FFAs bound in plasma?

A

99% of FFAs are bound to albumin
* high plasma [FFA] are found locally in adipose tissue during fat catabolism

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7
Q

How are fatty acids classified?

A
  • By chain length
  • By degree of saturation
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8
Q

What are the classifications of chain length for fatty acids?

A
  • short chain: ≤ 6 carbons
  • medium chain: 8-14 carbons
  • long chain: >14 carbons
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9
Q

What are the classifications for degrees of unsaturation?

A
  • saturated: no double bonds and every carbon is sp3 hybridized
  • unsaturated: 1 or more double bonds
  • monosaturated: 1 double bond therefore 2 adjacent carbons are sp2 hybridized
  • polyunsaturated: more than 1 double bond therefor more than 2 carbons are sp2 hybridized
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10
Q

What is the most common FA in the diet?

A

Palmitic Acid/ Hexadecanoic acic

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11
Q

What is the structure of palmitic acid?

A
  • chain length = 16 carbons
  • An acid end and a methyl end
  • C16H32O2
  • 16:0
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12
Q

What degrees of saturation can there be?

A

0, 1, 2, 3 double bonds
* saturated: all carbons bonded with H, so can compact together making them more stable and solid at room temperature
* Unsaturated: contains double bonds therefore less H atoms causing a kink such that they cannot stack easily are typically liquid at room temperature

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13
Q

What are the two types of nomenclature for fatty acids?

A
  • Miller notation
  • Omega notation
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14
Q

Describe the Miller notation nomenclature for fatty acids

A
  • 18:2n-6
  • 18= number of carbons in the
    whole molecule
    2= number of db bonds
    -6= subtract this value from n to derive the carbon atom where the last double bond starts (18-6=12), count from the carboxyl end
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15
Q

Describe the Omega notation nomenclature for fatty acids

A
  • 18:2ω6
  • 18= number of carbons in the whole molecule
  • 2= number of db bonds
  • ω=label for the last acyl carbon
  • 6 = the carbon number for the first double bond from the methyl end
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16
Q

Common Saturated fatty acids

A
  • Myristic acid 14:0
  • Palmitic acid 16:0
  • Stearic acid 18:0
  • Arachidic acid 20:0
  • Lignoceric acid 24:0
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17
Q

Common unsaturated fatty acids

A
  • Palmitoleic acid 16:1∆9 (n-7)
  • Oleic acid 18:1∆9 (n-9)
  • Linoleic acid 18:2∆9,12 (n-6)
  • 𝝰-linolenic acid 18:3∆9,12,15 (n-3)
  • Arachidonic acid 20:4∆5,8,11,14 (n-6)
  • Eicosapentaenoic acid 20:4∆5,8,11,14,17 (n-3)
  • Docohexaenoic acid 22:6∆4,7,10,13,16,19 (n-3)
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18
Q

Common short chain fatty acids (SCFAs)

A
  • Acetic acid 2:0
  • Propionic acid 3:0
  • Butyric acid 4:0 (butter)
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19
Q

Common medium chain fatty acids (MCFAs)

A
  • Caproic acid 6:0 (butter)
  • Caprylic acid 8:0
  • Lauric acid 12:0 (coconut & palm oils)
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20
Q

What is the notation for cis- and trans- unsaturated fatty acids?

A
  • cis- is implied
  • trans- is placed before the C#
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21
Q

How are polyunsaturated fatty acids with trans- notated?

A

c or cis, t or trans can be used in the name
* 18:2ct, 18:2tt or 18:2tc for isomers with 18 carbons and 2 double bonds

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22
Q

How are most trans found?

A

Mostly formed by industrial hydrogenation or by biohydrogenation in the stomachs of ruminant animals
* i.e. isomers of conjugated linoleic acid: c9,t11-CLA and t10,c12-CLA

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23
Q

How are most cis found?

A

Cis FAs more abundantly found in nature, therefore in the body as well

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24
Q

What is the effecy of TFA in the diet?

A

increased TFA diet will result in increased TFA in body fat stores and membranes
* Negative effect on health bi increasing CVD risk (↑LDL and ↓HDL)
* Adipose can be a biomarker of TFA intake

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25
Q

What about natural TFAs?

A

Some TFAs are naturally occuring such as those in cows and sheep milk and may have a positive effect on health
* still reccomended to reduce to less than 1%

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26
Q

What is the idea behind hydrogenation of fatty acids?

A

essentially to convert the more unsaturated (plant) fatty acids to saturated by adding in hydrogen and decreasing double bonds. This was initially thought to be a potential healthier alternative to saturated fats.

27
Q

What was the effect og hydrogenation of fatty acids?

A
  • changed functional properties such as melting point and mouth feel
  • bi-product was TFAs from partial hydrogenation so the cis arrangement changed to trans
28
Q

Sources of saturated fatty acids

A

keep in mind mixture of FAs

29
Q

Sources of TFAs

A

keep in mind mixture of FAs

30
Q

Structures of common fatty acids
* palmitic acid
* eliadic acid
* oleic acid
* linoleic acid
* arachidonic acid
* linolenic acid
* docosohexaenoic acid

A
31
Q

What are glycerolipids?

A

Main form of fat storage

32
Q

What are the types of glycerolipids?

A
  • MAG
  • DAG
  • TAG
33
Q

What is the most common glycerolipid in the body?

A

TAG
* SN1 and SN3 could be either SFA or USFA
* SN2 is usually an unsaturated fatty acid to keep fat in the body in the liquid phase otherwise our fat would be like butter

34
Q

Structure of TAG

A
  • glycerol backbone made up of 3 carbons SN1, SN2, SN3 with FAs linked via ester bond (alcohol + acid)
  • SN1 and SN3 are usually on the right and SN2 are usually on the left
  • SN2 is typically an USFA
  • Overall the fatty acids attached to the glycerol can be combination of SFAs, MUFAs, and PUFAs
35
Q

What is the reaction which links the FAs to the glycerol to form glycerolipids?

A

condensation reaction
* glycerol+3 fatty acids=tryglyceride+3H2O
* SN2 mainly unsaturated

36
Q

Simple vs. complex TG

A
  • simple: 3 FAs are the same
  • complex: 3 FAs are different
37
Q

What uses TAG as major lipid storage?

A

plants and higher animals

38
Q

Where else might fat be stored besides the adipose tissue?

A

yellow bone marrow
* made mostly of fat and contains stem cells that can become cartilage, fat, or bone cells.

39
Q

Properties of TG FAs

A
  • firmess
  • stability
  • oxidation of FAs
40
Q

How does firmness change between different TG FAs?

A

Generally: ↓ chain length or ↑ double bond results in ↑fluidity
* liquid at room temperature

41
Q

How does stability change between different TG FAs?

A

↓ chain length or ↑ double bonds results in ↓ stability
* more readily oxidized

42
Q

What FAs are most susceptible to oxidation?

A

PUFA

43
Q

What is the result of FA oxidation?

A
  • off/rancid/’warmed-over’ flavours and odours in the food
44
Q

What is used to prevent FA oxidation in foods?

A

tocopherols and butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT)
* preserve colour and flavour by preventing oxidation

45
Q

General dietary fat composition of
* animal fats
* tropical oils
* vegetable oils

A
46
Q

What are glycerophospholipids?

A

The main structural building blocks of cell membranes
* polar head group is hydrophillic and faces out

47
Q

Structure of phospholipids

A
  • glycerol backbone
  • FAs in positions sn-1 and sn-2
  • phosphate group in position sn-3
48
Q

How are glycerophospholipids classified?

A

classified according to head group
* phosphatidyl choline
* phosphatidyl ethanolamine
* phosphatidyl serine
* phosphatidyl inositol
* phosphatidyl glycerol

49
Q

What is the most common phospholipid?

A

phosphotidyl choline
* ~60%

50
Q

Functions of phospholipids (PPLs)

A

physiological
* cell membrane structure
* intracellular messengers
food industry
* emulsifiers: lecithin from egg yold, wheat germ, soy bean

51
Q

How is cholesterol present in the body?

A
  • free cholesterol
  • cholesterol esters
52
Q

Where are cholesterol esters typically found in the body?

A

in plasma cholesterol is esterified at the 3’OH group for storage and transport
* often arachidonic acid

53
Q

What is cholesterol a aprt of when plasma cholesterol levels are measured?

A

the cholesterol in part of the lipoproteins so either LDL or HDL

54
Q

Role of cholesterol in the body

A

Modulating membrane compressibility, permeability, fusibility, thickness and organization

55
Q

Where does dietary cholesterol come from?

A

animal source foods only

56
Q

What cholesterol do plants have?

A

phytosterols

57
Q

What cholesterol do plants have?

A

phytosterols

58
Q

What is cholesterol the precursor for?

A
  • parent compound for steroid hormones and are stored as precursors
  • precursor for bile acids
  • precursor for fat soluble vitamins (A, E, D, K)
59
Q

What are thr 5 major classes of steroid hormones?

A
  • androgens
  • estrogens
  • progestins
  • mineralcorticoids
  • glucocorticoids
60
Q

What are the classes of phytosterols?

A
  • β-sitosterol
  • campersterol
  • stigmasterol
61
Q

Role of bile acids

A
  • solubilize phospholipids and cholesterol (detergents)
  • Aid in digestion and absorption of fat and fat-soluble vitamins in the intestine
62
Q

What do bile acids conjugate with to be secreted as bile?

A

conjugate with taurine or glycine in the liver in the final step before being secreted
* Conjugation substantially reduces the passive reabsorption of the molecule through biological membranes.

63
Q

What can bile acid deficiency lead to?

A
  • fat malabsorption
  • malnutrition
  • gall-stones
  • celiac disease
  • ileal resection

NUTR 301 (32 decks)

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