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Medical Biochemistry > Ch. 16: Lipids I: FAs & Eicosanoids > Flashcards

Ch. 16: Lipids I: FAs & Eicosanoids Flashcards

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1
Q

How do you define lipids based on their solubility?

A

Soluble in non-polar solvents

Not very soluble in water

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2
Q

Which lipids are polar?

A

FAs
Cholesterol
Glycerophosphatides
Glycosphingolipids

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3
Q

Which lipids are non-polar?

A

Triacylglycerols

Cholesterol esters

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4
Q

Important functions of lipids?

A 
Thermal insulation (most impt)
Energy storage as TG
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5
Q

Difference bet saturated & unsaturated fats?

A

Saturated: No C=C

Unsaturated: C=C

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6
Q

Saturated FAs: Lauric acid

Molecular formula?

A

C12 H24 O2

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7
Q

Saturated FAs: Myristic acid

Molecular formula?

A

C14 H28 O2

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8
Q

Saturated FAs: Palmitic acid

Molecular formula?

A

C16 H32 O2

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9
Q

Saturated FAs: Stearic acid

Molecular formula?

A

C18 H36 O2

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10
Q

Saturated FAs: Arachidic acid

Molecular formula?

A

C20 H40 O2

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11
Q

FA Oxidation: how many net ATP made from 16C fat?

A

129 net ATP

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12
Q

Hormones that bind to receptors to metabolize TAG ➡️ DAG + FA?

3 enzymes involved?

A

Epinephrine, glucagon

1) adenylate cyclase
2) protein kinase
3) hormone-sensitive lipase

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13
Q

⬆️ FA oxidation indicative of what?

What is ⬆️ produced in liver? Made from what?

A

Starvation
DM

Ketone bodies
Acetyl CoA

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14
Q

Name 3 acyl-CoA synthases & what FAs they act on.

A

Acetyl-CoA synthase: acetate & low wt carboxylic acids

Medium-chain acyl-CoA synthase: FAs w/4-11 C

Acyl-CoA synthase: FAs w/6-20 C

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15
Q

How many ATP needed to activate FAs?

A

2 ATP used (➡️ 131-2 = 129 net ATP)

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16
Q

Activation step: FA + CoASH ➡️ acyl-CoA (thioester), using 2 ATP

Location? Enzyme involved?

A

On outer mitochondrial membrane

Acyl-CoA synthetase

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17
Q

Carnitine is synthesized from which a.a.?

A

Lys & Met

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18
Q

Transport of acyl-CoA ➡️ mitochondrial matrix:

1) Acyl-CoA + carnitine ➡️ ?
Enzyme?
Location of rxn?

A

Acylcarnitine + CoASH

Carnitine palmitoyl-transferase I (CPT I)
Intermembrane space

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19
Q

Transport of acyl-CoA ➡️ mitochondrial matrix:

2) Acylcarnitine ➡️ moved into mitochondrial matrix
Enzyme?

A

Carnitine-acylcarnitine translocase

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20
Q

Transport of acyl-CoA ➡️ mitochondrial matrix:

3) Acylcarnitine + CoASH ➡️ ?
Enzyme?
Location?

A

Acyl-CoA + carnitine

Carnitine-palmitoyl transferase II (CPT II)
mitochondrial matrix

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21
Q

What is an allosteric ➖ of CPTI in liver?

Fxn?

A

Malonyl CoA (Precursor for FA synthesis)

Prevents simultaneous FA oxidation & sythesis

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22
Q

What generally occurs in beta-oxidation?

1 run through cycle makes how much ATP?

A

Oxidation of acyl-CoA at beta C ➡️ 2 Cs removed as acetyl CoA

17 ATP

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23
Q

Beta oxidation: step 1?

Enzyme?

A

Acyl-CoA ➡️ alpha,beta-unsat. acyl-CoA / delta^2-unsat. acyl-CoA + FADH2

Acyl-CoA dehydrogenase

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24
Q

Beta oxidation: step 2?

Enzyme?

A

Alpha,beta- or delta^2-unsat. acyl-CoA ➡️ L-beta-hydroxyacyl-CoA

Enoyl-CoA hydratase

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25
Beta oxidation: step 3? Enzyme?
L-beta-hydroxyacyl-CoA ➡️ beta-ketoacyl-CoA + NADH L-beta-hydroxyacyl-CoA dehydrogenase
26
Beta oxidation: step 4? Enzyme?
Beta-ketoacyl-CoA ➡️ acyl-CoA + acetyl-CoA 3-ketoacyl-CoA thiolase
27
What can be done with the acetyl CoA produced from beta-oxidation?
1) TCA cycle 2) cholesterol synthesis (in cytosol) 3) form ketone bodies (liver)
28
Beta-oxidation energetics: palmitate How are 129 ATP obtained? (Breakdown)
7 FADH2 x 2 = 14 ATP 7 NADH x 3 = 21 ATP 8 acetyl CoA x 12 = 96 ATP - 2 ATP (FA activation)
29
Regulation of FA oxidation: Lipogenesis: ➕ and ➖ of acetyl-CoA carboxylase? (➖ and ➕ of FA oxidation)
➕ (➖ FA oxidation): insulin ➖ (➕ FA oxidation): Acyl-CoA, glucagon
30
How are VLCFAs (20 C or longer) oxidized?
1) initial beta-oxidation in peroxisomes (no ATP yield) | 2) shortened FAs (LCFAs) ➡️ mitochondria for further oxidation
31
What happens to the FADH2 produced in peroxisomal FA oxidation?
oxidized by O2 ➡️ H2O2 by catalase
32
3 disorders in peroxisomal FA oxidation? What occurs?
``` Zellweger's syndrome (formation of peroxisomes) Neonatal adrenoleukodystrophy (⬇️ breakdown of VLCFAs) Childhood adrenoleukodystrophy (same as #2) ``` Accumulation of VLCFAs in liver & CNS ➡️ severe neuro problems, death
33
What are sources of propionyl CoA?
Odd number FA oxidation Catabolism of Ile, Val, Met, Thr Oxidation of side chain of cholesterol
34
Oxidation of propionyl-CoA ➡️ ? ➡️ ? or ? Reactions require what vitamins?
Succinyl-CoA ➡️ oxidized or converted to glucose Biotin Vit B12
35
What generally occurs in alpha-oxidation of FAs?
Oxidation of LCFA ➡️ 2-OH FA ➡️ oxidation to FA w/one less C
36
Alpha-oxidation disorders: Refsum's disease? Resulting conditions?
Deficiency of phytanoyl-CoA hydroxylase ➡️ accumulation of phytanic acid Retinitis pigmentosa, failing night vision, peripheral neuropathy, cerebellar ataxia
37
What generally occurs in omega-oxidation of FAs? Catalyzed by a monooxygenase that requires ?
Oxidation of C atom most remote from carboxyl group in FA NADPH, O2, P-450
38
What are the products of omega oxidation of FAs?
Dicarboxylic acids ➡️ further oxidized from either end
39
How does oxidation of mono- & poly-unsaturated FAs differ?
Skips FAD+ step (since double bond already present)
40
General steps of ketone metabolism?
2 acetyl CoA ➡️ acetoacetyl CoA (+ acetyl CoA in) ➡️ HMG CoA ➡️ acetoacetate (+ acetyl CoA out) ➡️ acetone or 3-hydroxybutyrate
41
3 ketones generated in the body?
Acetoacetate Acetone 3-hydroxybutyrate
42
Where does ketogenesis take place? Cholesterol synthesis?
Ketogenesis: mitochondria Cholesterol synthesis: cytosol
43
How are ketone bodies generated in liver used by extra hepatic tissues?
1) 3-hydroxybutyrate ➡️ acetoacetate 2) Acetoacetate + succinyl CoA (TCA) ➡️ acetoacetyl CoA + succinate (TCA) (via thiophorase) 3) Acetoacetyl CoA ➡️ 2 acetyl CoA ➡️ TCA cycle
44
Regulation of ketogenesis: 1st point?
Lipolysis (TAG ➡️ FFA in adipocytes) ➕: glucagon, epi
45
Regulation of ketogenesis: 2nd point?
Transport of acyl CoA into MT matrix: Carnitine-palmitoyl transferase I (CPT-I) ➖: ⬆️ malonyl CoA
46
Regulation of ketogenesis: 3rd point?
Acetyl CoA ➡️ ketogenesis or TCA? Starvation: shunts acetyl CoA to ketogenesis (➖ TCA since oxaloacetate ➡️ PEP in gluconeogenesis)
47
What are long chain fatty acids synthesized from?
Dietary glucose (via pyruvate)
48
Where are the enzymes for fatty acid synthesis located in cell?
Cytosol (different enzymes from FA breakdown)
49
What is required for FA synthesis?
``` Reduced NADPH (from HMP shunt) ATP ```
50
What is initial & control step in FA synthesis? Enzyme? Requires what co-factor?
Acetyl CoA ➡️ Malonyl CoA (CO2 transfered from HCO3- ➡️ enzyme ➡️ acetyl CoA) Acetyl CoA carboxylase (requires biotin)
51
What are the 8 proteins (7 enzymes + carrier protein) that make up the FA synthase multi-enzyme complex?
``` Ketoacyl synthase Acetyl transacylase Malonyl transacylase Hydratase Enoyl reductase Ketoacyl reductase Acyl carrier protein (ACP) Thioesterase ```
52
FA synthase multi-enzyme complex: What vitamin does the acyl carrier protein (ACP) need? What important residue does it contain?
Pantothenic acid (4'-P-panthotheine) Contains SH residue (ketoacyl synthase also contains SH from Cys)
53
Where does the first acetyl group come from (to start FA synthesis)? What provides subsequent acetyl groups?
Acetyl CoA ("seed") Malonyl CoA Ex: C15 & C16 of palmitate is from acetyl CoA ➡️ C1-C14 from Malonyl CoA
54
What are the first 5 reactions (in order) of FA synthesis? Enzymes for each step?
1) priming reaction (acetyl transacylase / malonyl transacylase) 2) condensation (beta-ketoacyl synthase) 3) 1st reduction w/NADPH (beta-ketoacyl reductase) 4) dehydration (beta-hydroxyacyl dehydratase) 5) 2nd reduction w/NADPH (enoyl reductase)
55
After first 5 reactions of FA synthesis, what are the 2 possible following steps?
If acyl group is 16 C: enzyme loses affinity, releases palmitate (via thioester hydrolase) If acyl group is not yet 16 C: acyl group transferred to beta-ketoacyl synthase, return to reaction 1
56
What are the 3 generators of NADPH in the cytosol? (➡️ used in lipogenesis)
1) pentose P pathway 2) isocitrate dehydrogenase 3) malic enzyme
57
How is acetyl CoA used in lipogenesis obtained?
MT: Acetyl CoA + oxaloacetate ➡️ Citrate, moved out of MT ➡️ cytosol (via anti-port w/malate) ➡️ oxaloacetate + acetyl CoA (via ATP citrate lyase)
58
How are FAs with > 16 C (18-24 Cs) made?
Elongation of palmitate in ER or MT (liver)
59
What are the two essentials FAs? (Common name, omega series, systematic name, formula)
Linoleic acid (omega 6; 9,12-octadecadienoic; C18 H32 O2) Alpha-linolenic acid (omega 3; 9,12,15-octadecatrienoic; C18 H30 O2)
60
What important compounds are derived from the 2 essential FAs?
Linoleic acid ➡️ arachidonic acid Alpha-linolenic acid ➡️ docosahexaenoic acid (DHA)
61
Almost all naturally occurring, unsaturated LCFAs exist as which isomer?
Cis isomer
62
Unsaturated FAs: Palmitoleic acid Systematic name? Molecular formula? Omega series?
9-hexadecenoic C16 H30 O2 Omega 7
63
Unsaturated FAs: Oleic acid Systematic name? Molecular formula? Omega series?
9-octadecenoic C18 H34 O2 Omega 9
64
Unsaturated FAs: Arachidonic acid Systematic name? Molecular formula? Omega series?
5,8,11,14-eicosatetraenoic C20 H32 O2 Omega 6
65
Main 2 functions of unsaturated FAs?
1) fluidity of TG reserves, phospholipid membranes | 2) precursors of eicosanoids
66
What are the 2 most common monounsaturated FAs in mammals? How are their double bonds introduced?
Palmitoleic acid Oleic acid ER: double bond (bet C9-C10) via FA oxygenase (requires O2 & NADPH)
67
Arachidonic acid is precursor for what 4 compounds?
Prostaglandins (via cyclooxygenase) Thromboxanes Prostacyclins Leukotrienes (via 5-lipoxygenase)
68
How are EFAs (precursor FAs) stored? How are they released?
As esters of 2-position of glycerol backbone of cell membrane phospholipids Activation of appropriate phospholipase
69
What activates phospholipase A2 ➡️ release arachidonic acid?
Stimuli ➡️ Intracellular Ca2+ w/calmodulin ➡️ activates phospholipase A2 (and C)
70
What inhibits phospholipase A2 activity?
Glucocorticoids (cortisol)
71
Inhibitors of cyclooxygenase?
Aspirin Indomethacin Selective for COX2: Celecoxib, Rofecoxib
72
Synthesis of prostanoids: first 3 substrates?
Arachidonic acid ➡️ PGG2 ➡️ PGH2
73
Synthesis of prostanoids: 5 pathways from PGH2 PGH2 ➡️ PGI2 (➡️ 6-keto-PGF-1alpha) Enzyme?
prostacyclin synthase
74
Synthesis of prostanoids: 5 pathways from PGH2 PGH2 ➡️ PGE2 Enzyme?
PGE2 endoperoxide isomerase
75
Synthesis of prostanoids: 5 pathways from PGH2 PGH2 ➡️ PGD2 Enzyme?
PGD2 endoperoxide isomerase
76
Synthesis of prostanoids: 5 pathways from PGH2 PGH2 ➡️ PGF-2alpha Enzyme?
PGF-2alpha endoperoxide isomerase
77
Synthesis of prostanoids: 5 pathways from PGH2 PGH2 ➡️ TXA2 (➡️TXB2) Enzyme?
Thromboxane synthase
78
Eicosanoids: PGD2 Major site of synthesis? Major biological activities?
Mast cells ➖ platelet & leukocyte aggregation ➕ vasodilation, cAMP levels ⬇️ T cell proliferation, lymphocyte migration, IL-1a, IL-2
79
Eicosanoids: PGE2 Major site of synthesis? Major biological activities?
Kidney, spleen, heart ``` ➕vasodilation, cAMP levels ➕ uterine contractions ➕ platelet aggregation Keeps fetal ductus arteriosus open ⬇️ T cell proliferation, lymphocyte migration, IL-1a, IL-2 ```
80
Eicosanoids: PGF-2 alpha Major site of synthesis? Major biological activities?
Kidney, spleen, heart ➕ vasoconstriction ➕ bronchoconstriction ➕ smooth muscle contraction
81
Eicosanoids: PGH2 Major biological activities?
➕ platelet & leukocyte aggregation | ➕ vasoconstriction
82
Eicosanoids: PGI2 Major site of synthesis? Major biological activities?
Heart, vascular, endothelial cells ➖ platelet aggregation & leukocyte aggregation ➕ vasodilation, cAMP levels ⬇️ T cell proliferation, lymphocyte migration, IL-1a, IL-2
83
Eicosanoids: TXA2 Major site of synthesis? Major biological activities?
Platelets ➕ platelet aggregation ➕ vasoconstriction ➕ lymphocyte proliferation ➕ bronchoconstriction
84
Eicosanoids: TXB2 Major site of synthesis? Major biological activities?
Platelets ➕ vasoconstriction
85
Eicosanoids: LTB4 Major site of synthesis? Major biological activities?
Neutrophils, monocytes, eosinophils, basophils, mast cells, epithelial cells vascular permeability ➕ leukocyte chemotaxis & aggregation T cell proliferation, INF-gamma, IL-1, IL-2
86
Eicosanoids: LTC4 Major site of synthesis? Major biological activities?
Monocytes & alveolar macs, Eosinophils, Basophils, Mast cells, Epithelial cells ``` ➕ Microvascular vasoconstrictor Vascular permeability ➕ Bronchoconstriction ➕ INF-gamma Part of SRS-A ```
87
Eicosanoids: LTD4 Major site of synthesis? Major biological activities?
Monocytes & alveolar macs, eosinophils, mast cells, epithelial cells ``` ➕ Microvascular vasoconstrictor Vascular permeability ➕ Bronchoconstriction MAIN part of SRS-A ➕ INF-gamma ```
88
Eicosanoids: LTE4 Major site of synthesis? Major biological activities?
Basophils, mast cells Microvascular vasoconstrictor Bronchoconstriction Part of SRS-A

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