Lipids Flashcards
1
Q
Types of lipids
A
Fatty acids Triacylglycerols glycerolphospholipid sphingolipids isoprene based lipids waxes
2
Q
saturated
A
no double bonds
3
Q
unsaturated
A
double bonds
4
Q
palmitic acid
A
C16:0
get a present at sweet 16
5
Q
stearic acid
A
C18:0
you get to steer a car at 18
6
Q
oleic acid
A
C18:1
most abundant FA
7
Q
Linoleic acid
A
C18:2
8
Q
Arachidonic acid
A
C20:4
9
Q
unsaturated fatty acids
A
double bonds are Cis form
10
Q
Trans Fatty Acid
A
present at low levels in dairy and meat products
partially hydrogenated fats in foods contain much higher amts
11
Q
Triacylglycerols/triglycerides
A
major source of energy
stored in adipose tissue
glycerol backbone
esterified to 3 fatty acids
12
Q
Glycerolipids
A
glycerol back bone
fatty acids
ester linkage
phosphate - head groups
13
Q
phospholipids
A
glycerol backbone (3C)
can have ether linkage
fatty acid - ester
phosphate - head groups
14
Q
sphingolipids
A
sphingosine backbone (18C) fatty acid amide linkage phosphate-head group carbohydrate ceramide= parent molecule
15
Q
glycerophospholipds
A
saturated fatty acid C1
unsaturated fatty acid at C2
phosphate + head C3
phosphatidic acid= parent molecule
16
Q
examples of glycerophospholipids
A
phosphatidylcholine- lung surfactant phosphatidylethanolamine- inner leaflet PM phosphatidylserine- inner leaflet PM phosphatidylinositol- signaling cardiolipin - mitochondria
17
Q
Ether glycerophospholipid
A
ether bond at C1
fatty acid C2
phosphate + head - C3
18
Q
ether glycerophospholipid examples
A
plasmalogen
platelet activating factor - signaling , immune defense
short icicle chain at C2
19
Q
sphingolipid examples
A
sphingomyelin - ceramide + choline head, structure
glycolipids- ceramid + sugars
cerebroside- 1 sugar
ganglioside- 3+ sugar
20
Q
Steroids
A
isoprene based molecule has three 6-membered rings one 5 membered ring all fused together functions as salt balance, metabolic, sexual function
21
Q
Cholesterol
A
most common steroid
22
Q
Lipid Biosynthesis
A
intermediates in synthesis are linked to sulfylhydride groups of Acyl Carrier Proteins Cytosol Fatty Acid Synthase NADPH, Malonyl CoA Insulin Induced
23
Q
FormaFormation of Malonyl CoA activates
A
Acetate Units for Fatty acid synthase
24
Q
Fatty acid Synthesis strategy
A
add of 2C units to growing chain
driven by decarboxylation of Malonyl CoA
elongation rxn repeated until growing chain is C16:0
25
Fatty Acid Synthesis regulators
high glucose
high ATP
low AMP
fatty acyl coA low
26
Sources for fatty acid synthesis
carbohydrates- mainly
fatty acids
amino acids
27
Rate limiting step
Acetyl CoA carboxylase
| Acetyl CoA--> Malonyl CoA
28
Conversion of glucose to acetyl CoA for Fatty acid synthesis
```
Glucose enters liver
glycolysis
Pyruvate enters matrix
Pyruvate --> Citrate
Citrate leaves matrix
Citrate --> OAA + Acety l CoA
```
29
pyruvate carboxylase
```
pyruvate --> OAA
acetyl coA (+)
```
30
pyruvate dehydrogenase
```
pyruvate --> Acetyl CoA
acetyl CoA (-)
```
31
citrate lyase
citrate --> OAA + acetyl CoA
32
fate of citrate --> OAA
```
cytosolic malate dehydrogenase
malic enzyme
OAA--> malate--> pyruvate
NADPH is produced
uses ATP
induced by insulin
```
33
Acetyl CoA supplies carbons for fatty acid synthesis using
```
Acetyl CoA carboxylase
Biotin
CO2
citrate (+)
Rate limiting enzyme - target enzyme for lowering fat synthesis
```
34
what form is acetyl CoA carboxylase active?
nonphosphorylated
| bc it is insulin regulated --> PPI
35
Fatty Acid Synthase
1 protein- 7 active sites - Vit B5 (pantothenic acid)
1. Acyl Transferase- acetyl CoA primes the FA synthase
2. Malonyl transfer - SH react with malonyl CoA
3. Acetyl & Malonyl Condense
4. Reduction, Hydration, Reduction
7. Thioesterase- cleaves off FA
36
where does Palmitate C16:0 undergo elongation and unsaturation
in the ER
37
Elongation of FA requries
NADPH
Malonyl CoA
most prevalent form - Steric acid C18:0
38
Unsaturation of FA
steraroyl-CoA desaturase
stearoyl-CoA (C18:0) --> Oleoyl-CoA (C18:1)
involves cytochrome b5 and cytochrome b5 reductase
NADH
39
Arachidonic Acid synthesis
synthesized from linoleic acid (omega 6) C18:2
| arachidonic acid C20:4
40
essential fatty acids
```
linoleic acid (diet) C18: 2 omega 6
linolenic acid (diet) C 18:3 omega 3
```
41
EPA and DHA synthesis
from linolenic acid - omega 3
42
Fatty Acid Breakdown
```
intermediates in breakdown linked to SH groups of CoA
occurs in mitochondria
Beta oxidation
NADH, NAD+
glucagon induced
```
43
What is the name of the process that oxidizes fatty acids to acetyl CoA?
```
beta oxidation
oxidation
hydration
oxidation
thiolase
```
44
where does beta oxidation occur?
mitochondrial matrix
45
Entry of fatty acids is dependent on
fatty acid binding proteins
| diffusion
46
in circulation long chain fatty acids are bound to
albumin
47
in cytosol, fatty acid binding proteins releases
fatty acid from albumin
| and converts it to Fatty acyl CoA
48
Transport of Long Chain FA requires
acyl CoA synthetase
Carnitine Palmitoyl transferase I (CPT I) on outer membrane
Translocase
CPT II on inner membrane
49
Transport steps of FA
1. FA crosses PM using fatty acid binding proteins
2. fatty Acyl CoA diffuses outer membrane mito
3. CPT 1 converts fatty acyl CoA to fatty acyl-carnitine
4. fatty acyl-carnitine crosses inner membrane using translocate
5. CPT II converts fatty acyl carnitine back to fatty acyl CoA
50
Activation of Fatty Acids
formation of fatty acyl CoA - prereq to metabolism of Fatty acid in cell
Acyl CoA syntheses located in ER, outer mitochondrial membrane, peroxisomal membrane
51
Fatty Acyl CoA fates
membrane lipids- ER
storage - TriacylGlycerols - ER
energy- Beta oxidation, ketogenesis - mitochondria
52
Beta oxidation of LC FA enzymes
1. Acyl CoA dehydrogenase
2. hydrolase
3. dehydrogenase
4. thiolase
53
Beta oxidation products
Fatty acyl CoA (C-2) --> B oxidation spiral
| Acetyl CoA --> Krebs
54
Beta oxidation vs Glucose oxidation
FA-- 1 carbon: 8 ATP
Glucose -- 1 C : 6.3 ATP
utilize glucose stores 1st - faster metabolism
then fats used for long term--
fats give off more energy but takes longer to metabolize
55
oxidation of polyunsaturated fatty acid
cis bonds must be isomerize to Trans
reductase reduces conjugate bonds to 1 trans bond
Beta Oxidation relies on saturated FA
56
oxidation of medium chain fatty acids
medium chain fatty acids = more water soluble than long chain
does not go through intestinal digestion -- enter blood via hepatic portal vein
activated to CoA in liver
oxidized to Acetyl-CoA via B-oxidation
57
oxidation of odd chain fatty acids
beta oxidation of odd carbon FA yields--> Propionyl CoA (3C)
propionyl- CoA--> --> ---> Succinyl CoA
Biotin and B12
58
Ketone bodies
special source of fuel and energy for certain tissues
source of fuel for brain, heart, muscle
major source for brain during starvation
59
Where is ketone bodies made
produced in liver mitochondria matrix
but not used in the liver
can't be broken down
60
Ketone bodies reach target tissue mitochondria
converts back to acetoacetate and Beta hydroxybutyrate
61
ketone body synthesis
acetyl CoA --> acetoacetyl CoA
HMG CoA sythase and lyase
Acetoacetate --> Beta-hydroxybutyrate + Acetone
62
Synthesis of PC, PE, PS
Diacylglycerol --> phophatidylethanolamine / phosphatidylcholine
phosphatidylethanolamine --> phosphatidylcholine (use SAM)
Phosphatidylethanolamine --> phosphatidylserine
63
Synthesis of Cardiolipin and phosphatidylinositol
Phosphatidic acid
| ---> Cardiolipin and Phosphatidyinositol
64
Synthesis of Ether Glycerolipids
1. DHAP + Fatty Acyl-CoA = Form Ester
2. Fatty Acyl group exchanged for Fatty Alcohol= Fatty Acyl Alcohol
3. Ether linkage is Formed
4. Head group is added
65
etholamine plasmalogen
found in myelin
| synthesis occur in peroxisomes
66
choline plasmalogen
found in heart muscles
| synthesis occur peroxisomes
67
Degradation of glycerolipids
phospholipase A1 cut at Carbon 1
Phospholipase A2 cut at Carbon 2
Phospholipase C cut at Carbon 3 releasing phosphate + head
Phospholipase D- cut at phosphate releasing head group
68
phospholipases
in cell membranes or lysosomes
degraded based on needs of cell
tissue and organelle specific
69
sphingolipid biosynthesis
Serine + palmitoyl-CoA
--> Ceramide (precursor for sphingolipids)
sphingolipids found in outer leaflet, PM, ER, Golgi
70
Cholesterol Biosynthesis
occurs in Liver
1. begins in cytosol
2. uses 3 acetyl-CoAs
3. HMG-CoA reductase (rate limiting step)
4. Acetyl CoA--> maevalonate --> isoprene--->squalene
7. squalene--> lanosterol (1st ring formed) --> cholesterol
uses ATP and NADPH
71
Regulation of HMG-CoA reductase
```
dephosphorylated = active (fed)
phosphorylated = inactive
```
half -life = 3 hrs
increase in cholesterol decreases gene expression for reductase
72
Fates of cholesterol
- - bile salts
- cholesterol esters (via Acyl-CoA cholesterol acyl transferase (ACAT)
- hormones - progesterone, testosterone, cortisol, aldosterone
73
Statins lower serum cholesterol levels by
targeting HMG CoA reductase
| act as transition state analog
74
how are lipids transported throughout the body
lipoproteins
75
lipoproteins
cluster of lipids
monolayer membrane + apolipoprotein
polar surface = apolipoprotein, phospholipid, free cholesterol
nonpolar core- cholesteryl ester , TG, fats
76
apoproteins
protein w/o lipid
has structural role
activate certain enzymes for lipoprotein metabolism
serve as ligands
77
chylomicrons
apoB48, apo CII, apo E
apo CII activates Lipoprotein lipase (LPL) to release TG
remanants return to liver (driven by apoE receptors)
78
VLDL
```
apoB100
HDL donates apoCII and apoE to form mature VLDL
LPL VLDL
50 % remnants return to liver
50% remnants are in the form IDL
```
79
IDL metabolism
HTGL removes core TG
forming LDL
60% return to liver via apoB100
40% carried to extra hepatic tissue
80
LDL receptors
recognize apoB100 and apoE
binds all except for HDL
increasing cholesterol levels in cell inhibits LDL receptor synthesis
LDL receptor uptake= Endocytosis
81
HDL synthesis
synthesis by liver and intestines
| apoA1, apoAII, apoCI, apoCII
82
Maturation of nascent HDL
accumulates phospholipids and cholesterol from cells lining the blood vessel
transfer of lipids to nascent HDL does nor require enzymatic activity
"brings cholesterol to liver" = good
83
Reverse Cholesterol Transport
HDL remove cholesterol from ccells and return to liver
cells contain protein ABCA1 - use ATP hydrolysis to move cholesterol from inner to outer leaflet
HDL accepts cholesterol and modifies it
LCAT ensures cholesterol is linked to HDL
84
Fate of HDL cholesterol
HDL can bind to receptors on hepatocytes
scavenger receptor SR-B1
not an endocytic mechanism
85
HDL interacts with the lipoproteins
HDL converts nascent chylomicrons + VLDL --> mature form
CETP exchange pathway
transfer of cholesterol esters from HDL to VLDL in exchange for TG
86
ATherosclerosis
inflammatory disease driven by oxidized LDL
macrophages express scavenger receptors that bind oxidized LDL
leads to foam cells in arterial walls (filled with lipids)
oxidized LDL cholesterol linked to coronary artery disease
