Download Fatty acids and their derivatives

PTT103
BIOCHEMISTRY
LIPID
Pn Syazni Zainul Kamal
School of Bioprocess Engineering
Course outcome

Able to demonstrate basic structure,
properties, functions and classification of
important biomolecules
Outline
Lipid Classes
- Fatty acids and their derivatives
- Triacylglycerols
- Wax esters
- Phospholipids
 Membranes
- Membrane structure
- Membrane function

Introduction
diverse group of biomolecules
 eg. Fats, oils, phospholipids, steroids,
carotenoids
 Lipids – Those substances from living
organisms that dissolve in nonpolar solvents
eg. Ether, chloroform, acetone but not in
water.


Role & function as :
◦ structural components in cell membranes
(e.g phospolipids)
◦ means to store energy (e.g triacylglycerols)
◦ chemical signals, vitamins, or pigments,
◦ protective molecules (outer coatings for
cells).
Lipid classes
Fatty acids and their derivatives
 Triacylglycerols
 Wax esters
 Phospholipids
 Sphingolipids
 Isoprenoids

Fatty acids and their derivatives
Fatty acids – monocarboxylic acids that contain
hydrocarbon chains of variable length (12-20 C),
R-COOH
 2 types
saturated

(only carbon-carbon single bond)
unsaturated
(one/more double bonds)
- can occur in two isomeric forms; cis/trans
- cis : identical groups are on the same side of a double
bond
- Trans : identical groups are on opposite sides of a double
bond
Cis-isomers : Both R groups are
on the same side of the
carbon-carbon double bond
Trans-isomers : Have R groups
on different sides.
Monounsaturated : 1 double bond
Polyunsaturated : > 1 double bonds
Fatty acid structure
Examples of fatty acids
number of double bonds.
position of a double bond
Tot number of C
Plants & bacteria synthesize all fatty acids
 Mammals can synthesize saturated
&monounsaturated fatty acid. Other
unsaturated FA obtain from dietary
 Nonessential FA – can be synthesized
 Essential FA – obtain from diet (vege
oils,nuts,seeds)

Unsaturated FA do not pack as closely
together as saturated fatty acids  Less
energy is required to disrupt the
intermolecular forces between them 
have lower melting points and are liquids
at room temperature. For example, palmitic acid
A6:0), a saturated fatty acid, melts at, whereas palmitoleic acid
A6:1A9) melts at 0°C
Triacylglycerols
Ester of glycerol with 3 fatty acids
 Neutral fats – no charge
 Most contain FA of varying lengths, which
may be saturated, unsaturated or a
combination of both
 Referred as fats or oils depend on FA
composition
 Fats – solid at room temp, mostly
saturated FA

Fats – solid at room temp, mostly
saturated FA
 Oils – liquid at room temp, high
unsaturated FA
 In animals triacylglycerols (fats)
- store energy > efficiently than glycogen
- provide insulation at low temp
 In plants triacylglycerols (oils)
- energy reserve in fruits and seeds
- high amounts of unsaturated FA (eg oleic
& linoleic) soybean, peanut, olive

Wax esters
are esters formed from fatty acids and long chain
alcohols
 Nonpolar lipid
 Function – protective coating on leaves, stems,
fruits, skin and fur of animals
 carnauba wax – 32C carboxylic acid & 34C
alcohol component
 Beeswax – 26C carboxylic acid & 30C alcohol
component

Phospholipids
Roles :
1) Structural components of membranes
2) Emulsifying agents
3) Surface active agents (substance that
lowers surface tension of a liquid)
 Amphipathic molecule
 Have hydrophobic and hydrophilic
domains

Hydrophobic domain
- composed of hydrocarbon chains of fatty
acids
 Hydrophilic domain (polar head group)
- composed of phosphate & other charged
or polar group
 Suspended in water they spontaneously
rearrange into ordered structures

◦ Hydrophobic group exclude water
◦ Hydrophilic group exposed to water (Next slide)
◦ (Basis of membrane structure)
Phospholipid in aqueous solution

2 types phospholipids :

phosphoglycerides – mol contain glycerol,
fatty acids, phosphate, alcohol (eg choline).
Found in cell membrane

Sphingomyelins – contain sphingosine, fatty
acids, phoshate, alcohol
(classified as sphingolipid) – discuss later
Phosphoglycerides
Phosphatidic acid – precursor for other
phosphoglyceride mol
O
CH2O C R1
O
CH O C R2
O
CH2O P OH
O
Sphingolipids

Important membrane components of animal
& plant membranes

Contain log-chain amino alcohol (either
sphingosine or phytosphingosine) linked to
fatty acid mol by amide bond

3 subclasses – ceramide, sphingomyelin,
glycosphingolipid

Sphingomyelin
– animal cell membrane
- have a phosphorylcholine or
phosphoethanolamine molecule with an
ester linkage to the 1-hydroxy group of a
ceramide.

-
Glycosphingolipid
are ceramides with one or more sugar
residues joined in a β-glycosidic linkage at
the 1-hydroxyl position.
Classes :- Cerebrosides have a single glucose or
galactose at the 1-hydroxy position
- Sulfatides are sulfated cerebrosides
- Gangliosides have at least three sugars,
one of which must be sialic acid
-
sulfatides
gangliosides
Isoprenoids

Biomolecules contain repeating 5 carbon
structural units (isoprene units)
isoprene
Biosynthetic pathway begin with
formation of isopentenyl pyrophosphate
from acetyl-CoA
 Consist of terpenes and steroids


Terpenes
-
Classified according to number of isoprene
residues they contain :
-
Monoterpenes (2 isoprenes)
eg. geraniol in oil of geranium
Sesquiterpenes (3 isoprenes)
eg. Farnesene (part of citronella oil)
Diterpenes (4 isoprenes)
eg. Phytol, a plant alcohol
-
- Triterpenes (6 isoprene)
eg. Squalene in shark liver oil, olive oil
- Tetraterpenes (8 isoprene)
eg. Carotenoids, orange pigment
- Polyterpene (Thousands isoprene)
eg. Rubber (3000-6000 isoprene)

Steroids
-
Complex derivatives of triterpenes
Eukaryotes & some bacteria
Composed of 4 fused rings
Distinguished from each other by placement
of carbon-carbon double bonds and various
constituents (OH, Carbonyl & alkyl groups)
Eg cholesterol, progesterone, testosterone,
estradiol
-
-

-
-
Cholesterol
Important mol in animals cell membrane
& precursor for synthesis of vit D
Possesses 2 methyl (C-18 & C-19),
attached to C-13 & C-10 & a double
bond
Has a OH group (sterol)