Lipids

1
Lipids

• Broadly defined as naturally occurring
  non-polar compounds having simple functional
  groups.

2
Major Categories of Lipids

• Fats and Oils
• Biosynthesis of fatty acids
• Phospholipids
• Waxes
• Terpenes
• Steroids
• Prostaglandins

3
Fats

• Esters of fatty (long chain carboxylic) acids
• Common are triacyl glycerols, which can be
  hydrolyzed (saponified) into soaps

4
Micelles mode of action of soap
H2O
Soap (above) can be represented as
H2O
H2O
H2O
Soap (and detergents) form spherical
clusters (right) called micelles micelles
surround and dissolve non-polar substances (oily

stains) and render them soluble.
H2O
Oil
H2O
5
Oils (polyunsaturated fats)
Presence of cis double bonds in oils makes it
difficult for the molecules to pack regularly in
a solid structure oils have lower melting
points than fats, and are liquids at RT.
6
Biosynthesis of Fatty Acids

• Repetitive applications of thio-Claisen
• reactions explains why most fatty acids
• have an even number of carbon atoms

7
Enolization / Carboxylation of Acetyl Coenzyme A
8
Acylation of Malonyl Coenzyme A with 2 Carbon unit
Enol form
9
Decarboxylation, Reduction, Dehydration and
Reduction
10
Acylation of Malonyl Co A with 4 carbon unit
(4 carbon unit)
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Conversion to 6 carbon unit
(6 carbon unit)
12
Acylation of Malonyl Co A with 6 carbon unit
(6 carbon unit)
13
Conversion to 8 carbon unit...etc.
(8 carbon unit)
14
Common Saturated Fatty Acids
15
Common Unsaturated Fatty Acids
16
Polyunsaturated Fatty Acids

• Polyunsaturated fatty acids (PUFAs) include
  those having two and three double bonds.
• Omega-3 fatty acids are those unsaturated
  fatty acids that have a double bond between the
  third and fourth carbon from the end of the
  carbon chain (opposite the CO2H group).
• A common omega-3 fatty acid found in fish oil
  is linolenic acid
• Omega-3 fatty acids are considered beneficial
  for brain function.

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Composition of Fats and Oils

• lauric myristic palmitic
  stearic oleic linoleic
• C12 C14 C16 C18 C18(1) C18(2)
• Animal Fats
• Lard - 1 25 8 50 10
• Beef Fat - -
  27 14 50
  3
• Butter Fat 2 10 29 10 27 5
• Human Fat 1 3 25 8 46 10
• Whale Blubber - 8 12 3 35 10
• Vegetable Oils
• Coconut oil 48 18 11 2 7 1
• Corn oil - 1 10 3 45 35
• Olive oil - 1 7 3 82 6
• Peanut oil - - 7 5 58 24
• Soybean oil - - 10 2 29 51

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Fats and Oils in Nuts

• Nut g. prot./oz. g. fat/oz
  satd MUFAs PUFAs
• Walnuts 4 18 10
  15 75
• Almonds 6 14
  10 65 25
• Hazelnuts 4 17
  9 77 14
• Cashews 4 13
  21 62 17
• Macadamia 2 22
  16 76 8
• Pecans 3 20
  9 53 28
• Peanuts 7 14
  16 52 32

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Phospholipids

• Phospholipids are long-chain fatty esters of
  glycerol also containing a phosphoric acid
  derivative.
• They contain a glycerol backbone, like fats and
  oils, but they have a phosphate group with an
  ionic alkyl ammonium group also attached.

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Representative Phospholipids
Phosphatidylcholine (lecithin)
Phosphatidylethanolamine (cephalin)
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Phospholipids
Can be represented as
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Lipid Bilayer of Cell Membranes
Outside the cell (aqueous)
Cell membrane
Inside the cell (aqueous)
23
Waxes

• Long chain esters of long chain fatty acids

(present in beeswax)
24
Terpenes

• Derived biosynthetically from a branched five
  carbon unit, isopentyl pyrophosphate

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Terpenes...

• Common monoterpenes (C10)

26
Some more common terpenes
27
Steroids

• Involved in regulatory processes and in sexual
  characteristics and functions
• Common steroids include cholesterol, estradiol,
  testosterone, estrone and progesterone

C
D
C
D
A
B
A
B
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Some Common Steroids
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More Common Steroids
30
More Common Steroids
31
Prostaglandins

• C20 carboxylic acids that contain a 5-member ring
  and have two long side chains.
• They were first isolated from prostate glands of
  sheep, but now they are known to have widespread
  distribution among tissues, and to exhibit an
  extraordinarily wide range of biological effects.

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Representative Structures
Biosynthetic source arachidonic acid
Prostaglandin E1 (PGE1)
Prostaglandin F2a (PGF2a)
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Some Varied Biological Effects of Prostaglandins

• Lower blood pressure
• Affect clotting of blood
• Lower gastric secretions
• Promote inflammation (countered by aspirin, which
  inhibits PG biosynthesis)
• Affect reproductive systems
• Stimulate uterine contractions during childbirth

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Final Exam

• Review
• No formal review session is scheduled.
  I will be available for questions during exam
  week.
• Final Exam
• TR class Tue., Dec. 11, 1130
  am - 230 pm Dobo Hall,
  room 205.
• MWF class Wed., Dec. 12, 800-1100 am
• Dobo Hall, room 132