1
Q
What are the types of fatty acids?
A
- Saturated fatty acids
- Unsaturated fatty acids (monounsaturated and polyunsaturated)
2
Q
A
Myristate; 14:0
3
Q
A
Palmitate; 16:0
4
Q
A
Stearate; 18:0
5
Q
A
Oleate
6
Q
A
Arachidonate
7
Q
What are saturated fatty acids?
A
Hydrocarbon chain contains only fully reduced methylene groups (no double bonds)
8
Q
What are unsaturated fatty acids?
A
1 or more C=C double bonds in hydrocarbon chain
9
Q
What are monounsaturated fatty acids?
A
Contain 1 C=C double bonds in hydrocarbon chain
10
Q
What are polyunsaturated fatty acids?
A
Contain multiple C=C double bonds in hydrocarbon chain
11
Q
What are essential fatty acids?
A
Humans must obtain them in diet because we don’t have the enzymes to synthesize them
12
Q
List some essential fatty acids.
A
- Linoleate
- α-linolenate
- Arachidonate
13
Q
What does a cis isomer look like?
A
14
Q
What does a trans isomer look like?
A
15
Q
Are most fatty acids cis or trans?
A
Cis
16
Q
Do long-chain saturated fatty acids have a higher or lower melting point than long-chain unsaturated fatty acids? Why?
A
Higher MP because of differences in intermolecular interactions
17
Q
TAGs containing mostly saturated fatty acids have a _____ MP.
A
Higher
18
Q
TAGs containing mostly unsaturated fatty acids have a _____ MP.
A
Lower
19
Q
What is hydrogenation?
A
Process of heating unsaturated fatty acids in presence of hydrogen to reduce C=C double bonds (increase degree of saturation)
20
Q
What is a trans fat?
A
Unsaturated fatty acid where C=C double bond is in the trans configuration instead of cis
21
Q
Do plant vs. animal trans fats pose the same risks?
A
Yes
22
Q
How are carbons in fatty acids usually numbered?
A
From carboxylic acid end (carboxyl carbon is C-1)
23
Q
How are positions of C=C bonds in polyunsaturated fatty acids often identified?
A
Identified using methyl carbon (omega-carbon)
24
Q
What is an omega-6 fatty acid?
A
Unsaturated fatty acid where the double bond is 6 carbons away from the terminal methyl carbon
25
What is an example of an omega-6 fatty acid?
Linoleic acid
26
What is an omega-3 fatty acid?
Unsaturated fatty acid where the double bond is **3** carbons away from the terminal methyl carbon
27
What is an example of an omega-3 fatty acid?
α-linoleic acid
28
What is α-linoleic acid converted to?
Eicosapentaenoic acid (**EPA**) and docosahexanoic acid (**DHA**)
29
Why are omega-3 fatty acids good?
They're associated with a decreased risk of cardiovascular disease
30
What is lipidomics?
Large-scale investigation of structures and functions of the complete set of lipids in a biological system
31
What are waxes?
Lipid composed of **long-chain fatty alcohols esterified to long-chain fatty acids**
32
Why are waxes solids in biological contexts?
The MP of long-chain saturated wax esters is usually higher than ambient temperature
33
What are adipocytes?
Fat cell; site of TAG storage
34
Why are TAGs a major form of stored energy?
- Fatty acids are at a higher reduction state than glucose, so they **yield more energy per number of carbons** upon oxidation in mitochondrial matrix
- Hydrophobic nature means they are not solvated by water so they **have less mass for the same amount of stored energy as glycogen**
35
Where do we obtain TAGs from?
Diet or synthesized in liver
36
What is a lipoprotein?
Molecular complex made of **hydrophobic lipid core surrounded by shell of polar lipids and apolipoproteins**
37
What transports dietary TAGs?
Chylomicrons
38
What are lipases?
Water-soluble enzyme that **hydrolyzes TAGs into free fatty acids and glycerol**
39
What is colipase?
Regulatory protein associated with pancreatic lipase
- Enhances lipase function by binding bile acids, which inhibit lipase function
40
What are chylomicrons?
Large lipoprotein particles that **transport TAGs** from intestines to tissues throughout body
41
What do apolipoproteins do?
**Promote lipoprotein particle formation** in endomembrane system
42
Biosynthesis of TAGs in animals uses __1__ produced by degradation of __2__ and __3__ to generate __4__ in cytosol.
1. Acetyl-CoA
2. Carbs
3. Proteins
4. Palmitate
43
What are lipid droplets?
Aggregate of TAG molecules surrounded by phospholipid monolayer in adipocyte cytoplasm
- **Where TAGs are stored**
44
What is perilipin?
Monolayer-embedded protein forming **shell of adipocyte lipid droplets**
- Prevents TAG degradation by endogenous adipocyte lipases
45
What are the 3 major lipases in human adipocytes?
1. Adipose triglyceride lipase
2. Hormone-sensitive lipase
3. Monoacylglycerol lipase
46
How does glucagon signaling lead to fatty acid release into the bloodstream?
1. Activation of the glucagon receptor leads to **GDP–GTP exchange in the Gsα protein**, which stimulates **cyclic AMP production** by the enzyme adenylate cyclase
2. Glucagon downstream signal is transmitted by cyclic AMP activation of PKA, which **phosphorylates perilipin** on the surface of lipid droplets and hormone-sensitive lipase
3. Conformational change that promotes **binding of regulatory protein G58 to adipose triglyceride lipase**
4. Hydrolysis reaction that cleaves a fatty acid from the stored triacylglycerols to **generate diacylglycerol and a free fatty acids**
5. Phosphorylated hormone-sensitive lipase also associates with perilipin on the lipid droplet surface, where it **produces a free fatty acid from diacylglycerol to produce monoacylglycerol**
6. Monoacylglycerol lipase then **generates a free fatty acid and glycerol from monoacylglycerol**
7. **Albumin transports the free fatty acids** through the circulatory system to tissue
47
Glycerol
48
Triacylglycerol
49
What are the 3 major types of membrane lipids?
1. Glycerophospholipids
2. Sphingolipids
3. Cholesterol
50
What are glycerophospholipids?
Membrane lipid composed of **glycerol linked to 2 fatty acid chains and a phosphate group, which is bound to a polar head moiety**
51
What are the 4 types of glycerophospholipids?
1. Phosphatidylcholine
2. Phosphatidylserine
3. Phosphatidylethanolamine
4. Phosphatidylinositol
52
What are sphingolipids?
Molecules containing **sphingosine bound to a single fatty acid chain**
53
What are sphingophospholipids?
**Sphingolipids linked to a phosphate group** that's connected to a **polar head group**
- Sphingomyelin
54
What are the 2 types of sphingolipids?
1. Sphingophospholipids
2. Sphingoglycolipids
55
What are the 2 types of sphingoglycolipids?
1. Cerebrosides
2. Gangliosides
56
What kind of lipid are cerebrosides? What is the general structure of cerebrosides?
- Type of sphingolipid
- Contain **glucose or galactose bound to the terminal hydroxyl group**
57
What are gangliosides?
**Cerebrosides with an oligosaccharide** bound to the terminal glucose or galactose
58
What is the fluid mosaic model?
Membrane is a 2D solution in which many membrane proteins are both oriented across the membrane and free to move laterally through the membrane
59
What are lipids rafts?
Aggregation of membrane proteins that form densely packed complexes
60
What is the function of lipid rafts?
Thought to serve as sites for **cell signaling, membrane trafficking, and neurotransmission**
61
What is the most abundant membrane lipid?
Glycerophospholipids
62
What is phosphotidate a precursor for?
Precursor for many common glycerophospholipids
63
What is this?
Phosphotidate
64
What is 1?
Phosphatidylserine
65
What is 2?
Phosphatidylethanolamine
66
What is 3?
Phosphatidylcholine
67
What is 4?
Phosphatidylinositol
68
Identify the sites of phospholipase action.
69
What is sphingosine?
Long-chain amino alcohol derived from palmitate
70
What is ceramide a precursor for? What is its structure?
- Precursor of cerebrosides, gangliosides, and sphingolipids
- Sphingosine covalently linked to a fatty acid
71
Ceramide
72
Sphingomyelin
73
What do gangliosides have a role in?
Cell recognition and membrane function
74
What is Tay-Sachs disease?
Genetic disease of sphingolipid metabolism due to defective **hexosaminidase A**, which causes GM2 gangliosides to accumulate
75
What is Fabry disease?
Genetic disease of sphingolipid metabolism due to a defect in **α-galactosidase A**, which causes ceramide trihexoside to accumulate
76
What is Niemann-Pick disease?
Genetic disease of sphingolipid metabolism due to a mutation in the **gene for sphingomyelinase**, which blocks the conversion of sphingomyelin to ceramide
77
What causes the symptoms of Tay Sachs disease vs. Fabry disease and Niemann-Pick disease?
- Tay-Sachs sympotoms are due to excess levels of the GM2 substrate
- Fabry and Niemann-Pick symptoms are due to the accumulation of metabolic precursors
78
Cholesterol
79
What are eicosanoids?
Group of **immune system signaling molecules** derived from long-chain polyunsaturated fatty acids
80
What do cholesterol derivatives regulate?
Activity of nuclear receptor proteins
81
What are bile acids?
Polar molecules derived from cholesterol that are secreted into intestines where they **emulsify dietary lipids (aids in lipid absorption)**
82
What is the major bile acid in humans?
Glycocholate
83
What are steroid hormones?
**Ligands for nuclear receptor proteins**, which mediate hormone signals by altering the expression of specific genes
84
What is rickets?
Disease caused by vitamin D deficiency
- Results in inadequate calcium deposition in cartilage and bone
85
Where does over 90% of vitamin D in the human body come from?
Sunlight conversion of 7-dehydrocholesterol
86
7-Dehydrocholesterol
87
Vitamin D3
88
25-Hydroxyvitamin D3
89
1,25-Hydroxyvitamin D3
90
What is vitamin D3?
Precursor to the biologically active form of vitamin D
91
What are eicosanoids derived from?
Arachidonate
92
Eicosanoids are released from ___ by ___.
Membranes, phospholipases
93
What are eicosanoids modified by?
Mitochondrial enzymes
94
What are the 4 major classes of eicosanoids?
1. Prostaglandins
2. Prostacyclins
3. Thromboxanes
4. Leukotrienes
95
What are the local effects of prostaglandins?
- Regulating blood flow
- Stimulating inflammation
- Controlling ion transport
- Initiating contractions during birth
96
What are prostacyclins?
Eicosanoid derived from prostaglandin H2 that **regulates platelet aggregation and blood clotting**
97
What are NSAIDS?
Inhibitor of prostaglandin H2 that is used to reduce inflammation
98
Compare and contrast COX-1 and COX-2.
- Related in terms of overall 3D structure and similar catalytic activities
- COX-1: constitutively expressed; involved in **producing prostaglandins** that stimulate mucin secretion and **protect the stomach lining from low pH**
- COX-2: specifically expressed; responsible for **producing prostaglandins** that **cause inflammation**
99
What causes the side effects of NSAIDs like stomach bleeding?
COX-2 is the relevant biological target, but NSAIDs inhibit both COX-1 and COX-2 so the stomach isn't protected from low pH
100
What transports TAGs synthesized in the liver?
VLDL particles
101
What transports TAGs stored in adipose tissue?
Albumin
102
What are the steps of the absorption and transport of dietary TAGs?
1. **Emulsification** of triacylglycerols by bile acids
2. **Hydrolysis of TAGs** by intestinal lipases to **generate free fatty acids**
3. **Resynthesis of TAGs** inside intestinal epithelial cells
4. Packaging of TAGs into **chylomicrons**
5. Export of chylomicrons into **lymphatic system**
6. Entry if chylomicrons into **circulatory system**
103
Diagram the conversion of 7-dehydrocholesterol to 1,25-hydroxyvitamin D
104
When are fatty acids released? (At rest vs. exercise)
During exercise
Biochem 2 (CHEM 441B)
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