Metabolism II: Lipid Metabolism Flashcards
(84 cards)
1
Q
Two essential features of fatty acids
A
- long hydrocarbon chain
- carboxylic acid group
2
Q
What is the most common chain length of the long hydrocarbon chain in FAs?
A
12-24 carbons
3
Q
Long hydrocarbon chain of FA features
A
- chain typically linear
- usually contains even number of carbons
- 4 - 30 Carbons
4
Q
The FAs that occur naturally arise primarily through variation of what?
A
chain length
degree of saturation
5
Q
What is one way FAs can be classified
A
based on number of double bonds
6
Q
What type of FA has 0 double bonds?
A
saturated
7
Q
What type of FA has one double bond
A
monounsaturated
8
Q
What type of FA has 2 or more double bond?
A
polyunsaturated
9
Q
What is an example of a saturated FA?
A
Stearic acid
10
Q
What is an example of a monounsaturated FA?
A
Oleic acid
11
Q
What is an example of a polyunsaturated FA?
A
Linoleum acid
12
Q
What is the most commonly synthesized FA?
A
palmitic acid
13
Q
What type of FAs cannot be synthesized in the body?
A
essential
14
Q
w-6 and w-3 FAs are examples of what kind of FA?
A
essential
15
Q
w-6 FA
A
Linoleum acid
18:2
16
Q
w-3 FA
A
linolenic acid
18:3
17
Q
What are linoleum acid and linolenic acid mainly produced by?
A
plants
18
Q
Sources of FAs
A
- diet
- de novo lipogenesis
- mobilization from adipose tissue
19
Q
Where are FAs stored as in adipocytes?
A
triacylglycerol
- constantly hydrolyzed and resynthesized
20
Q
Adipocytes
A
metabolically very active
21
Q
What is R1 of triacylglycerol often?
A
palmitate
22
Q
What is R2 of triacylglycerol often?
A
oleate
23
Q
What is R3 of triacylglycerol often?
A
oleate or a polyunsaturated fatty acyl group
24
Q
What type of FA is released from the adipocytes?
A
nonesterfied FA
25
The release of nonesterfied FAs from the adipocytes are initiated by...
hormone sensitive lipase (HSL)
26
What are the final products of triacylglycerol hydrolysis?
glycerol
| nonesterfied FAs
27
What is HSL activated by?
- epinephrine
- norepinephrine
- ACTH
- glucagon
- acting via phosphorylation of enzyme
28
What is HSL inhibited by?
insulin
29
What are nonesterfied FAs bound to for transport to other tissues?
serum albumin
30
What are the major target tissues of nonesterfied FAs?
muscle and liver
31
How are nonesterfied FAs taken up at the target cells?
passively
32
What happens to the nonesterfied FAs when they are within the target cells?
- found to fatty acid binding protein
| - then must be activated
33
What type of cells are FAs taken up by?
- cells where they may serve as precursors in the synthesis of other compounds
- fuels for energy production
- substrates for ketone body synthesis
34
When would FAs be exported to other tissues?
to be used for energy production
35
What are ways FAs are synthesized for?
storage or export
36
What occurs during FA activation
Fatty acid converted to fatty acyl CoAs
37
What is the enzyme used during FA activation?
acyl CoA synthetases
38
What are fatty acyl CoAs bound to to enter the mitochondria?
carnitine
| Becomes acyl carnitine
39
How does carnitine and acyl CoAs convert to acyl carnitine?
carnitine palmitoyl transferase I
40
How is acyl carnitine transferred into the mitochondria?
acyl carnitine transporter
41
What happens to acyl carnitine when it enters the mitochondria
- becomes acyl carnitine + CoA-SH
42
How does acyl carnitine separate in the mitochondria?
with CPTII
| - becomes Acyl CoA + free carnitine
43
What happens to the acyl CoA once in the mitochondria?
B-oxidation --> Acetyl CoA
44
What is the end product of B-oxidation?
Acetyl CoA
45
Where can B-oxidation occur?
mitochondria and peroxisomes
46
What are the preferred substrates for peroxisomal B-oxidation?
very long chain FAs
47
How many ATP are generated from one FA molecule?
106
48
What are the types of oxidation of FAs?
- a
- b
- w
49
A-oxidation of FAs
- Carbon atoms removed one at a time
50
What is the end product of a-oxidation?
propionyl CoA
51
Where does a-oxidation occur?
peroxisomes
52
Where does w-oxidation occur?
microsomes
53
What is w-oxidation carried out by?
CYP450 4A1
54
w-oxidation of FAs
- mono carboxylic FAs converted to dicarboxylic FAs
| - then dicarboxylic FAs undergo b-oxidation
55
Where are ketone bodies produced?
liver
56
Where are ketone bodies used?
Peripherally as an energy source when glucose is not readily available
57
What are ketone bodies synthesized from?
acetyl CoA
58
Where does ketone body synthesis occur?
hepatic mitochondria
59
Ketone body production
- acetoacetate produced in three step process
| - acetoacetate reduced to beta-hydroxy butyrate
60
What is ketone body production regulated by?
availability of acetyl CoA
61
When does the rate of ketone body production increase?
during starvation
62
FA synthesis
process of combining 8 two C fragments to form a 16 C saturated FA (palmitate)
63
What are the two C fragments combined during FA synthesis?
acetyl groups from acetyl CoA
64
Palmitate and FA synthesis
Can be modified to give rise to other FAs
65
What modifications can be done during FA synthesis?
- chain elongation to give longer FAs
| - desaturation: gives unsaturated FAs
66
Where does FA synthesis occur?
primarily in cytoplasm of these tissues:
- liver
- adipose
- CNS
- lactating mammary gland
67
What is the rate limiting step in the synthesis of FAs?
Acetyl CoA --> Malonyl CoA
68
What is the enzyme used during the rate limiting step in the synthesis of FAs?
Acetyl CoA carboxylase
69
FA synthase complex
- acyl carrier protein
- acetyl CoA-ACP transacetylase
- Malonyl CoA-ACP transacetylase
- B-ketoacyl-ACP synthase
- B-ketoacyl-ACP reductase
- B-hydroxyacyl-ACP dehydrates
- Enoyl-ACP reductase
70
What does one round of FA synthesis produce?
Butyryl-ACP (4C)
71
When does the FA synthesis stop?
When 16C (palmitic acid) is produced
72
What can happen to excess FAs in the liver?
- plasma lipoproteins
- B-oxidation
- plasma free FAs
73
Where can acetyl CoA go?
- cholesterol
- CAC
- FAs in liver
- ketone bodies in blood
74
What is FA metabolism regulated by?
energy need of a cell
75
What regulates the availability of glucose or FAs for use by a cell?
insulin
| glucagon
76
What happens during the fed state in the liver?
- Insulin stimulates FA synthesis
- Increases the levels of key enzymes
- Insulin increases NADPH
- Activating phosphorylation phosphatase
77
What does the activation of phosphorylation phosphatase do?
dephosphorylates ACC
78
What happens during the fed state in adipose tissue?
- insulin promotes lipid storage
- insulin increases glucose uptake by inducing Glut-4
- glucose provides glycerol for TG biosynthesis
- Insulin inhibits lipolysis
79
What does the inhibition of lipolysis do?
dephosphorylates hormone sensitive lipase
80
What happens during the fasted state in the liver?
- insulin levels decrease
- glucagon levels increase
- FA synthesis decreases
- Acyl CoA carboxylase inhibited by phosphorylation
- Glycolysis decreases (reduces the supply of acetyl CoA)
- Ketone body production increases
81
What happens during the fasted state in the adipose tissue?
- insulin levels decrease
- glucagon levels increase
- glucagon activates hormone sensitive lipase
- adipose tissue lipolysis occurs
- free FAs are delivered to liver, muscle, etc
82
Regulation of FA oxidation during the fed state
- FA oxidation decreases due to increased ACC activity
- ACC produces malonyl CoA (precursor for new FAs)
- Malonyl CoA also inhibits CPT-1
83
What occurs during FA metabolism in the fasting state?
- AT lipolysis
- FA oxidation
- ketone bodies
- glycerol-gluconeogenesis
84
What is excess FAs stored as during the fed state?
TAG in adipose
