Exam 4 Flashcards
A chemically diverse group of molecules characterized by their solubility in organic solvents
Lipids
Have little or no solubility in water
Lipids
Biological functions of lipids
- Principle form of energy storage
- Account for approximately 50% of the mass of biological membranes
- Enzyme cofactors, electron carriers, light-absorbing pigments hydrophobic anchors, emulsifying agents, hormones, intracellular messengers…
Biological membranes composition
50% Lipids 50% Proteins
2 categories of lipids
- Neutral Lipids
2. Polar Lipids
Neutral Lipids
Fatty Acids, Triacylglycerols, Diglyceride, Monoglyceride, Wax, Eicosanoids, Polyprenyl Lipids
Carboxylic acids having hydrocarbon chains of 4-36 carbons
Fatty Acid
General structure of Fatty acids
COOH(CH2)nCH3
n=4-36
Short hand system for fatty acids
Specifies carbon number and the number and location of the double bonds
12:0
CH3(CH2)10COOH = Lauric Acid
Lauric Acid
12:0
CH3(CH2)10COOH
14:0
CH3(CH2)12COOH = Myristic Acid
Myristic Acid
14:0
CH3(CH2)12COOH
16:0
CH3(CH2)14COOH = Palmitic Acid
Palmitic Acid
16:0
CH3(CH2)14COOH
18:0
CH3(CH2)16COOH = Stearic Acid
Stearic Acid
18:0
CH3(CH2)16COOH
20:0
CH3(CH2)18COOH = Arachidic Acid
Arachidic Acid
20:0
CH3(CH2)18COOH
24:0
CH3(CH2)22COOH = Lignoceric Acid
16:1 (Delta 9)
CH3(CH2)5CH=CH(CH2)7COOH
Palmitoleic Acid
CH3(CH2)10COOH
Lauric Acid
CH3(CH2)12COOH
Myrisitic Acid
CH3(CH2)14COOH
Palmitic Acid
CH3(CH2)16COOH
Stearic Acid
CH3(CH2)18COOH
Arachidic Acid
CH3(CH2)22COOH
Lignoceric Acid
Palmitoleic Acid
16:1 (Delta 9)
CH3(CH2)5CH=CH(CH2)7COOH
Palmitoleic Acid
18:1 (Delta 9)
CH3(CH2)7CH=CH(CH2)7COOH
Oleic Acid
Oleic Acid
18:1 (Delta 9)
CH3(CH2)7CH=CH(CH2)7COOH
CH3(CH2)7CH=CH(CH2)7COOH
Oleic Acid
18:2 (Delta 9, 12)
CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH
Linoleic Acid
Linoleic Acid
18:2 (Delta 9, 12)
CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH
CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH
Linoleic Acid
18:3 (Delta 9, 12, 15)
CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
Alpha Linolenic Acid
Alpha Linolenic Acid
18:3 (Delta 9, 12 , 15)
CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
Alpha Linolenic Acid
20:4 (Delta 5, 8, 11, 14)
CH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH
Arachidonic Acid
Arachidonic Acid
20:4 (Delta 5, 8, 11, 14)
CH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH
CH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH
Arachidonic Acid
One Double bond Carbon Skeleton
Palmitoleic Acid
Oleic Acid
Two Double Bond Carbon Skeleton
Linoleic Acid
Three Double Bond Carbon Skeleton
Alpha Linolenic Acid
Four Double Bond Carbon Skeleton
Arachidonic Acid
No Double Bond Carbon Skeleton
Lauric, Myristic, Palmitic, Stearic, Arachidic, Lignoceric (ACIDS)
Double bonds are usually
Cis
Fatty acids usually have ______ number of carbons
even
Fatty Acids are categorized as
Neutral lipids
At physiological pH, fatty acids exist in the
Anionic form with an ionized caroxylate (COO-)
Fatty acids have an average pKa of
4.5
The physical state of lipids is largely due to
how the fatty acids are packed
Kinks in the chain from double bonds cause packing to be
loose
Lower unsaturated =
Tighter packaging = solid
Unsaturated fatty acids are subject to
Oxidative cleavage of double bonds
The bad taste and smell of fatty foods is due to
short chain aldehydes and shorter chain carboxylic acids
Fatty acid chain length and degrees of unsaturation have an influence on
Melting point
Fatty acids with most carbon with no double bonds have
Have the highest Melting point
12: 0 = 44.2
18: 0 = 69,6
18: 1 = 13.4
Triacylglycerols are
Neutral lipids
Composed of 3 fatty acids in ester linkage with glycerol
Triacylglycerol
Acyl =
fatty acid
Acylation =
addition of fatty acid
Diglyceride
2 fatty acids
1 alcohol
signals reactions in cells
Monoglyceride
1 fatty acid
2 alcohols
Triglycerides
3 fatty acids
no alcohol left from glycerol
most natural fats contain large amounts of
Triacylglycerols
Different, but characteristic, fatty acids compositions of triacylglycerols depend on
the origin of the fat
Long chain of fatty acids esterified to a long chain fatty alcohol
Wax
COMPLETELY insoluble in water
Wax
Wax is categorized as
Neutral lipid
Formed from the oxidation and cyclization of the fatty acids arachidonic acid (20:4)
Eicosanoids
Eicosanoids are categorized as
Neutral lipids
Prostaglandins (PGs), Thromboxanes, and Leukotrienes are examples of
Eicosanoids
All are potent physiological regulators
Eicosanoids
Regulate blood pressure, induce labor, induce blood clotting
PGE2C and related PGs
Eicosanoids
All are synthesized from the 5 carbon precursor molecule isoprene
Polyprenyl lipids
Polyprenyl lipids are categorized as
Neutral lipids
Include sterols (steroids), lipid vitamins, and terpenes
Polyprenyl lipids
Limonene, Bactoprenol, Testosterone, Sodium cholate
Polyprenyl lipids
Have a characteristic cyclic nucleus consisting of 4 fused rings (3 6carbon rings, 1 5carbon ring)
Sterols
Have an attached fatty acids and are even more hydrophobic than cholesterol itself
Cholesterol Esters
Found in blood lipoproteins and function in cholesterol transport and storage
Cholesterol Esters
Rentinol (A), Calciol (D), E, K
Lipid vitamins (polyprenyl)
These are amphipathic lipids and are generally found in membranes
Polar lipids
Polar lipids are
amphipathic
Polar lipids are generally found in
membrane
A large group of lipids are referred to as
glycerophospholipids
Glycerolphospholipids are also known as
Phosphoglycerides
Phosphatides
Phospholipids
Phospholipids are built on a backbone structure of
glycerol-3-phsophate
Only membrane containing Di-P-G
Mitochondria
Phsopholipids are cleaved (degraded) by highly specific enzymes known as
phospholipases
4 most common phospholipases
- Phospholipase A1
- Phospholipase A2
- Phospholipase C
- Phospholipase D
The action of _______ results in the formation of a lysophospholipid
PLA
PLA
Results in the formation of a lysophospholipid
Phospholipases play a _______ important rol in certain types of transmembrane signaling
VERY
Many types of venom contain _______ amounts of Phospholipase .
Large
Cobra venom, rattlesnake venom, bee venoms
Another large group of lipids is the group known as
Sphingolipids
Amphipathic molecules generally found in membranes
Sphingolipids
Structurally based on sphigosine
Sphingolipids
Sphingolipids backbone structure
Ceramide: resembles glycerol in phospholipds
Be able to identify structures
Don’t have to draw them
3 groups of sphingolipids
- Sphingomyelins
- Glycosphingolipids
- Gangliosides
Also classified as a phospholipid due to the phosphocholine moiety
Sphingomyelins
Present in the myelin sheath of nerve cells
Sphingomyelins
Have one or more sugars attached to the ceramide moiety and contain no phosphate
Glycosphingolipids
The most complex sphingolipids with elaborate oligosaccharides as their polar head groups and always contain 1 or more slalic groups
Gangliosides