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Lipids Flashcards

1
Q

Fatty acids

A

Carboxylic acids
* Long hydrocarbon “tail”
* Saturated or unsaturated

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2
Q

Unsaturation in natural fatty acids are almost always…

A

Cis

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3
Q

What polyunsaturated fatty acids must we obtain from diet?

A
  • Linoleic acid (omega-6)
  • Alpha linolenic acid (ALA) (omega-3)
  • Eicosapentaenoic acid (EPA)
  • Docosahexaenoic acid (DHA)
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4
Q

Waxes

A

Monoesters of long-chained fatty acids and long-chained alcohols

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5
Q

How are natural fats and oils normally found?

A

Triesters
* Triacylglycerides
* Triglycerides

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6
Q

Do the 3 fatty acids in triesters have the be the same?

A

No, they can be the same or different

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7
Q

Highly saturated fats are…

A

Solids

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8
Q

Highly unsaturated fats are…

A

Oils/liquids

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9
Q

Claisen condensation

A

Nucleophilic acyl substitution using carbanions

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10
Q

What are the two modifications in modified Claisen condensation?

A
  1. Use thioesters instead of oxygen esters (more electrophilic than oxygen esters)
  2. Use carbanion equivalents
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11
Q

What is malonyl thioester made from?

A

Acetyl thioester
* Using ATP and Biotin

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12
Q

What is biotin?

A

A CO2 carrier
* Gets CO2 dissolved as bicarbonate

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13
Q

What is the process of making malonyl thioester?

A
  1. ATP phosphorylates HCO3 to form carboxyphosphate
  2. Carboxybiotin is formed
  3. Carboxyl group is transfered onto acetyl-CoA
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14
Q

How long are fatty acids typically synthesized as?

A

C16 molecule

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15
Q

What is fatty acid synthesis done with?

A

Done on a multi-enzyme complex: Fatty Acid Synthase (FAS)

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16
Q

What is the growing strand attached to to prevent diffusion?

A

Acyl carrier protein (ACP)

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17
Q

What is ACP made with?

A

Pantothenic acid + others, and a thiol group

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18
Q

What happens in each step in the conversion of acetyl-CoA to a 4 carbon acyl chain?

A
  1. Acetyl thioester
  2. Malonyl thioester (add on CO2)
  3. Decarboxylate as you add the groups together
  4. Reduce beta keto group to hydroxide
  5. Dehydrate hydroxide to alkene
  6. Reduce alkene to alkane
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19
Q

Where does the carbon acyl chain form on the FAS?

A

Forms on the ACP

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20
Q

What happens when the carbon acyl chain is fully formed on the FAS?

A

Switches from ACP binding to the electrophile binding cleft

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21
Q

Where is the growing fatty acid chain always attached to?

A

ACP (with is attached to FAS)

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22
Q

The growing fatty acid chain is the ——-, and it grows at the ——– end

A
  1. Electrophile
  2. Thioester
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23
Q

The nucleophile in fatty acid chain growth is always ——–

A

Malonyl thioester

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24
Q

What does malonyl thioester add onto the fatty acid chain?

A

Acetyl group

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25
What performs reduction in fatty acid synthesis?
NADPH
26
Why is the reduction of an alkene possible in fatty acid synthesis?
Conjugation with the thioester group makes the carbon have a electrophilic character
27
What is the addition of a nucleophile to the beta carbon of an alpha, beta- unsaturated carbonyl known as?
Conjugate addition * Michael addition
28
Hydrolysis of triacylglycerides is performed by...
Lipase enzymes
29
What is formed in the hydrolysis of triacyglycerides?
Glycerol + 3 fatty acid chains
30
What can glycerol be converted into?
DHAP (glycolysis intermediate)
31
What is required for glycerol to convert into DHAP?
1. Phosphorylation with ATP 2. Oxidation with NAD+
32
What does beta-oxidation do to fatty acids?
Beta carbon is oxidized from an alkyl carbon to a ketone * Degrades it into acetyl CoA
33
# Beta-oxidation: First Step
Convert fatty acid to CoA thioester 1. Convert to ester by adding AMP (using ATP) 2. Convert to thioester with HS-CoA
34
# Beta-oxidation: Second Step
FAD oxidizes the saturated tail * Makes FADH2
35
# Beta-oxidation: Third Step
Conjugate addition of water * After water is added, NAD+ is oxidized
36
# Beta-oxidation: Last Step
Cysteine residue of enzyme expels acetyl CoA as a leaving group * Enolate of acetyl CoA is protonated as it departs
37
Soaps
Metal salts of fatty acids
38
How are soaps prepared?
Base hydrolysis of triglycerides
39
Are sodium salts soluble?
Sodium salts are soluble at low concentrations * At high sodium concentrations, the salt will precipitate
40
Micelles
Formed by attraction of hydrophobic tails due to hydrophobic forces
41
What is one major problem with soaps?
Sodium and potassium salts of carboxylates are quite soluble * Carboxylates precipitates in the presence of polyvalent ions (Ca2+ etc.)
42
43
Soaps perform poorly in hard water because...
They will precipitate out due to the presence of polyvalent ions
44
How are synthetic detergents classified?
Nature of the hydrophilic head 1. Anionic 2. Cationic 3. Non-polar
45
What are two examples of anionic synthetic detergents?
1. Alkylbenzene sulfonates 2. Sulfate monoester (sodium dodecylsulfate etc.)
46
What is the first step in making alkylbenzene sulfonates?
Acid-catalyzed, self-polymerization of propylene (electrophilic addition to alkenes)
47
What was the ideal length of the tail in detergents?
12 carbons * Too long were too insoluble * Too small didn't form micelles
48
What is the second step in making alkylbenzene sulfonates?
Reacting the tail with benzene via Electrophilic Aromatic Substitution (EAS)
49
What is the final step in alkylbenzene sulfonate formation?
Sulfonation (EAS reaction) * Treated with base to yield the sodium sulfonate salt
50
What are cationic detergents typically?
Quaternary ammonium salts
51
What are examples of non-ionic detergents?
1. Ethoxylated alcohols 2. Ethoxylated phenols 3. Alkyl glucosides
52
What was the purpose of phosphate based additives?
Chelating polyvalent ions
53
What was the issue with phosphate additives? What was the alternative?
Phosphate was fertilizers, causes algal blooms * Solution: Silicates
54
What is the skeletal structure of phosphatidic acid?
Glycerol esterified to 2 fatty acids and 1 phosphoric acid
55
Terpenes
Naturally occurring compounds have carbon skeletons that contain multiples of 5 carbon atoms
56
What is the structural unit of terpenes?
Isoprene
57
# Terpene naming: 10 carbons
Monoterpene * 2 isoprene units * 1 heat-to-tail linkage
58
# Terpene naming: 15 carbons
Sesquiterpene * 3 isoprene units * 2 head-to-tail linkages
59
# Terpene naming: 20 carbons
Diterpene * 4 isoprene units * 3 head-to-tail linkages
60
# Terpene naming: 25 (rare) carbons
Sesterterpene * 5 isoprene units * 4 head-to-tail linkages
61
# Terpene naming: 30 carbons
Triterpene * 2 sesquiterpenes (15 carbons) linked tail-to-tail
62
# Terpene naming: 40 carbons
Tetraterpene * 2 diterpenes (20 carbons) linked tail-to-tail
63
What are the precursors for terpene biosynthesis?
C5 units 1. Dimethylallyl pyrophosphate (DMA-OPP) 2. Isopentenyl pyrophosphate (IP-OPP)
64
What are the roles od DMA-OPP and IP-OPP in the reaction?
DMA-OPP = Electrophile IP-OPP = Nucleophile
65
What does the reaction between DMA-OPP and IP-OPP form?
Geranyl-OPP * 10 carbons, 1 head-to-tail link
66
How long can geranyl-OPP be extended with IMA OPP?
Maximum 20 carbons long * 15 carbons is Farnesyl-OPP * 20 carbons is Geranylgeranyl-OPP Can be used to make sesquiterpenes and diterpenes
67
Where does DMA-OPP and IP-OPP come from?
Beta-keto thioester
68
What is the intermediate in IP-OPP and DMA-OPP formation?
Mevalonic acid
69
Steroids
4 rings fused together * 3 6-membered rings * 1 5-membered ring
70
How are the rings fused together in steroids?
Fused in a trans manner
71
What is lanosterol made from?
Squalene
72
What are the 2 fat-soluble vitamins?
Vitamin A Vitamin E

My Packs: (UWO) (CHEM 2223) (6 decks)

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