Download Glycerol + Fatty acids

BCM 3000
PRINCIPLES OF
BIOCHEMISTRY
(Semester 1 -2011/12)
1
LIPID
Learning outcome (Objectives)
● Function and distribution.
● Characteristics of fatty acids-structure and
chemical properties.
● Saturated and unsaturated fatty acids .
● Structures and properties of phospholipids,
sphingolipids, waxes, terpenes and steroids.
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???????
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LIPID
DEFINITION : General definition – all
compounds called fat and oils
TECHNICAL DEFINITION
Fat
: Triglycerides in the form of solids at
room temperature
Oils
:
Triglycerides which are liquid at
room temperature
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General Definition
Any natural compound which is insoluble or
nearly insoluble in water but soluble in nonpolar solvents –
a. Chloroform
b. CS2
c. Ether
d. warm or
e. hot ethanol
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FUNCTIONS
Lipids are widely distributed in both animal and plant
systems and perform a wide variety of functions
i.
Structural functions - Components of membranes
ii.
Storage forms of carbon and energy
iii.
precursor for major compounds – e.g. hormones.
iv.
Insulators - thermal, electrical or physical shock
v.
protective coatings – prevent infections, loss or
addition of compounds
vi.
Regulators - as vitamins & hormones
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CLASSIFICATION
1.
SIMPLE LIPIDS
Fatty acid esters
(Acid + alcohol  ester)
2.
COMPPOUND LIPID
Fatty acid + alcohol + OTHER COMPOUNDS
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LIPID
Acyglycerols
Waxes
COMPONENTS
(Glycerol + Fatty acids)
=
Alcohol + fatty acids
SIMPLE LIPIDS
???
Esters
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COMPOUND LIPIDS
4 types of Compound lipid
i.
Phosphoglycerides
ii.
Sphingolipids
iii.
Cerebrosides
iv.
Gangliosides
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LIPID
COMPONENTS
i
Phosphoglycerides
Glycerol + Fatty acid
+HPO42- + satu OHR
ii
Sphingolipids
Sphingosine + Fatty acid +
HPO42- + Choline
Cerebrosides
Sphingosine +Fatty acid +
Simple sugar
Gangliosides
Sphingosine + Fatty acid+ 26 Simple sugar (Including
sialic acid)
iii
iv
COMPOUND LIPID
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i & ii
=
Phospholipid - presence of
phosphate
ii , iii & iv =
Sphingolipids - presence of
Sphingosine
iii & iv
glycolipid - presence of
carbohydrate
=
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GLYCEROL –
Trihydroxy alcohol
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FATTY ACIDS
●
Long chain aliphatic carboxylic acids- contains
carboxyl group – polar head and `tail’ containing
hydrocarbon chain
●
Amphiphilic compounds – hydrophilic head and
hydrophobic tail
●
COOH can be ionised
●
Monocarboxyilic acids – linear hydrocarbon chain,
even carbon numbers – between C12-C20
●
Short, longer , branched, cyclic and odd numbers
also exist BUT not many
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Octadenic
acid
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FATTY ACIDS
2 TYPES
1. Saturated Fatty acids
2. Unsaturated Fatty acids
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Structure of Fatty Acids - Saturated
Fats
● mostly from animal sources,
● have all single bonds between the carbons in
their fatty acid tails, thus all the carbons are also
bonded to the maximum number of hydrogens
possible.
● saturated fats
● The hydrocarbon chains in these fatty acids are,
thus, fairly straight and can pack closely together,
making these fats solid at room temperature.
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Saturated fatty acid –e.g.
1. palmitic acid (CH3(CH2)14COOH) (16C) &
2. Stearic acid (CH3(CH2)16COOH)
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Saturated Fatty Acids
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Structure of Fatty Acids - Unsaturated
● Unsaturation normally at - C18 & C20 –
double bond separated by methylene group
-CH = CH - CH2 - CH = CH
● Double bonds = cis configuration
● Unsaturated fatty acid - oleic (18:1),
Linoleic (18:2), Linolenic (18:3) &
arachidonic (18:4)
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Unsaturated fatty acids
● C=C double bond arranged in two ways
● In cis bonds, the two pieces of the carbon chain on
either side of the double bond are either both “up”
or both “down,” such that both are on the same side
of the molecule
● In trans bonds, the two pieces of the molecule are on
opposite sides of the double bond, that is, one “up”
and one “down” across from each other
● Naturally-occurring unsaturated vegetable oils have
almost all cis bonds, but using oil for frying causes
some of the cis bonds to convert to trans bonds
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TRANS
CIS
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Unsaturated Fatty Acids
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● fatty acids with trans bonds are
carcinogenic, or cancer-causing.
● containing products such as margarine are
quite high,
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Oils
●
●
●
●
●
mostly from plant sources,
have some double bonds between some of the
carbons in the hydrocarbon tail, causing bends or
“kinks” in the shape of the molecules.
Because some of the carbons share double bonds,
they’re not bonded to as many hydrogens
oils are called unsaturated fats.
kinks unsaturated fats can’t pack as closely
together, making them liquid at room temperature
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CIS
TRANS
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Making margarine
● Vegetable oils often contain high proportions of
polyunsaturated and mono-unsaturated fats
(oils)  liquids at room temperature.
● You can "harden" (raise the melting point of) the
oil by hydrogenating it in the presence of a
nickel catalyst.
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SIMPLE LIPIDS
2 GROUPS
i. Neutral acyglycerols (e.g.
Triacylglycerol)
ii. Waxes
Acyglycerols
= glyceride = a tryhydroxy alcohol ester
= glycerol + fatty acid (3 different fatty
acids)
= can be esterified
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Glycerol = trihydroxy
alcohol
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TRIACYGLYCEROLS
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● Triacylglycerol – the most abundant
● No ionic groups -  neutral lipids
● Triacylglycerol = neutral fats (solids)
@ neutral oils (liquid)
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FUNCTIONS IN ANIMALS
I.
Adipose tissues - `fat depots' = storage forms of
carbon and energy
II. Transport - chylomicrons - = lipoprotein – fatty
acids are transported through lymphatic system
and blood  tissue adipose tissues and other
organs
III. `Physical protection' - e.g. temperature.
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
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WAXES
● Also an ester - alcohol & fatty acid
= very long hydrocarbon chain –
commercial application
● hairs, skin, leaves, fruits
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WAXES
Asid Oleic
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CHEMICAL CHARACTERISTICS OF TRYACYLGLYCEROL
(Reactions of Triacylglycerol)
1. Hydrogenation
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Double bonds in vegetable oils can be
hydrogenated  oils become solids – can control -
e.g.. peanut butter - crunchy, creamy
HYDROGENATION PROCESS
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2. Halogenation – Addition of halogens
Other halides - Iodine(I2), Chlorides (Cl2)
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●
Saturated fatty acid – iodine number = 0
●
Oleic acid - 90,
●
linoleic- 181,
●
Linolenic = 274
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● Animal fat-iodine number is low
● Vegetable oils – iodine number is high
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3. Hydrolysis
(i.)
Base Hydrolysis  Fatty acid + Glycerol or Salts of
fatty acid + Glycerol
● inside cells – by enzymes (lipase) – very
specific for ester bonds – products are
glycerol + fatty acids
● Non-enzymatic- with alkali (base)  salts of
fatty acid + Glycerol
● salts of fatty acids = soap
Base Hydrolysis =
SAPONIFICATION
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SAPONIFICATION
● The reaction of triacylglycerol with base (alkali) e.g.. NaOH, KOH
● Triacylglycerol – presence of strong ester bond
● Ester bond can be hydrolyzed by base  salts of
fatty acid + glycerol
Salts = soap – react as a soap/detergent
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Saponification reaction
(Base Hydrolysis)
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If R= palmitic acid  Sodium palmitate
If R’= oleic acid  Sodium oleate
R”= stearic acid  Sodium stearate
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Detergent? =`surface active agents' – lower
surface tension of surface of water
H2O = `poor cleansing agent - Y?  Because
the molecule is very polar and tend to stick to
each other – therefore cannot enter non-polar
areas like grease, oil, dirt
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HOW DOES A DETERGENT WORK ??
i.
Hydrophobic tails enters grease layers
ii. Hydrophilic heads come into contact with
aqueous layer  separate grease layer from the
surface
iii. Small grease globules form- `pincushion‘
iv. These globules have similar charges - therefore
cannot go near each other – can wash
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Water
Grease
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Head Polar
(hidrofilik)
EkorTak polar
(Hidrofobik)
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(ii). Acid Hydrolysis
Carboxylic acids
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4. RANCIDITY
Expose triacylglycerol to warm and moist
air  rancid (tengik)
2 reactions take place
1. Ester hydrolysis
2. Oxidation of the double bonds
● Hydrolysis - water (inside the lipid) + enzyme
(bacteria in the air)
● Oxidation-by O2 on the side chain of
triacylglycerol  short chain fatty acids –
rancid (tengik)
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Phosphoglycerides
Phosphoglycerides = Phosphoglycerol
i.e. they are derived from glycerol
Fatty acids
Glycerol
Phosphate group
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Glycerol @ other alcohols
Phosphoglycerol =
Phosphoglyceride
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Glycerol
(Trihydroxyglycerol)
Phosphatidic acid
(Glycerol + 2 fatty acids + Phosphate)
Phosphoglyceride (Phosphoglycerol)
(Glycerol + 2 fatty acids + Phosphate + other
group e.g.. alcohol)
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All phosphoglycerides
are Phospholipids!!!!
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Phosphoglycerides can be further esterified to
form  other lipids
i.
Phosphatidylcholine ( choline ester)
ii.
Phosphatidylethanolamine (ethanolamine)
iii. Phosphatidylserine (serine)
 All are important components of
membranes
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Asid lemak
Phosphate
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Phosphatidylethanolamine
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Phosphatidylethanolamine
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Phosphatidylserine
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Membrane
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SPHINGOLIPID
●
No glycerol – replaced with amine alcohol =
Sphingosine
●
Number of carbon atoms –varies
●
The simplest = ceramides = Fatty acid + sphingosine
through amino group via amide bond
●
Sphingomyelin – an example of sphingolipid - 1o
alcohol esterified to phosphate
 amino alcohol (= choline)
Found in nerve membranes and brain
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SPHINGOLIPID
1. What is the main structure for sphingolipid?
Sphingosine
2. Draw the structure of sphingosine
3. Draw the structure of glycerol and compare between
the two
CHCH(CH2)12CH3

CHOH

Sphingosine
CH NH2

CH2OH
H2C OH

H2COH

H2C OH
Glycerol
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SPHINGOLIPID
●
No glycerol – replaced with amine alcohol =
Sphingosine
●
●
Number of carbon atoms –varies
The simplest = ceramides = Fatty acid + sphingosine
through amino group via amide bond
Sphingomyelin – an example of sphingolipid - 1o
alcohol esterified to phosphate
●
 amino alcohol (= choline)
Found in nerve membranes and brain
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CERAMIDE
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Phosphate
Choline
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GLYCOLIPID
● When a carbohydrate is attached to OH- via
glycosidic bond
● Seb. induk = ceramide (sphingolipid) + CHO
● Cerebroside - CHO = glucose @ galactose
●
 glucocerebroside
● GANGLIOSIDE – ALSO contains oligosaccharide +
sialic acid
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DERIVED LIPIDS
● A heterogeneous group
● Derived from fatty acids
● steroids, prostaglandin, leukotriene, carotenoids,
vitamin
STEROID
All organisms – similar basic structure – fused ring=
perhydrocylopentanophenanthrene
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STEROL
i.
Hydrocarbon chain (C18-C20) at C17
ii. Hydroxyl group (OH) at C3
●
Main example = CHOLESTEROL – structural
component of membrane - 0 -40% lipid
membrane. Rigid
●
Precursor of bile, sex hormones, vit. D.
●
Role in atherosclerosis
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Hydrocarbon chain
at C17
OH at C3
CHOLESTEROL
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TERPENE
●
Lipid derived from isoprene
●
Term used for all compounds synthesized from the
precursor isoprene  cholesterol, bile acid, steroid,
lipid soluble vitamins = terpene
●
Oils from turpentine (pine tree extracts)
●
formula C10H15
●
> 15 carbon atom also found - `multiples of 5
●
Also in other plants
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TERPENE
Terpene with 20 carbon atoms - vit. A
- 40 carbon atoms - b- carotene
EXAMPLES:
1. monoterpene - Limonene - `odor' lemon
2. Diterpene - Gibberrelic acid – plant hormone
3. Triterpene - Squalene – Cholesterol precursor
4. Tetraterpene - Lycopene - tomato pigments
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TERPENE
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TERPENE
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TERPENE
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BCM 3000
PRINCIPLES OF
BIOCHEMISTRY
(Semester 1 -2011/12)
98
LIPID BEHAVIOUR IN WATER
●
Lipid – not soluble in water but can still be found in
aqueous environment
●
behavior in water important to understand the
phenomena
●
A lot of lipids are amphiphyllic = having
 hydrophobic part (hydrocarbon chain)
 polar (ionic) part
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When lipid is dispersed in water, the
hydrophobic part will segregate from the
solvent through `self-aggregation' – form
a. micelles – which are dispersed in water
b. monolayers ( aggregate – boundary
H2O: air
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MICELLES
MONOLAYER
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The tendency for hydrocarbon chains to
distance away from polar solvents gives rise to
= HYDROPHOBIC EFFECT
●
Most lipids will form micelles – spheres,
ellipse, discs, cylinders
●
Also can form vesicles – bilayer –
hydrocarbon chains are opposite to each
other  `hollow sphere'
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Micelle
Vesicles
Bilayer
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BILAYER
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Cholesterol does not form micelles ??
 Not amphiphatic compounds
 Structure – flat fused ring -  solid –difficult to
form micelles
Can form mixed micelle with amphiphatic lipids
mixed micelles – with amphiphatic lipids
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BILE ACID AND BILE SALTS
Bile acids serve many functions.
●
They aid in fat absorption
●
Bile acids are produced from cholesterol in the liver.
●
Cholesterol is converted to the carboxylic acids
cholic and chenodeoxycholic acid, which are the
primary bile acids in most species.
●
The liver conjugates the acids to either glycine or
taurine and subsequently secrets them into the bile.
●
The gall bladder serves to store bile acids until
contraction associated with feeding
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Glycine
Taurine
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LIPOPROTEIN
 Particles that contain lipid and protein
 bonds = not (non-covalent) bonds
 Function – In blood plasma – to transport
triacylglycerol and cholesterol
STRUCTURE
- form `micelle like particles' i.
core – non-polar triacylglycerol
ii. Surrounded by a layer of amphiphilic protein,
phospholipid and cholesterol
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Various categories – depending on the functions
i.
CHYLOMICRON – Carries exogenous triacylglycerols
& cholesterol (from diet) from intestine to the
tissues.
ii. LDL, IDL & LDL – group of related particles which
carry endogenous triacylglycerols & cholesterol
(produced internally) from the liver to tissues
NB: liver can synthesize triacylglycerol from excess
carbohydrate
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CHYLOMICRON
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LDL, CHOLESTEROL & ATHEROSCLEROSIS
Cholesterol –
● Important component of membrane – can be
supplied from the outside or internally (if not
enough)
● How obtained externally ? – ENDOCYTOSIS –
Through reaction of specific receptors = LDL
receptor?
● protein part of LDL tie up to R-LDL in the cell
complex  `pinched off' = endocytosis
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ENDOCYTOSIS vs
EXOCYTOSIS
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Protein – recycled – used in the cell
Oversupply ? –

Synthesis of R-LDL inhibited  low LDL  cholesterol
level in blood increases  deposited in the artery 
heart disease; stroke
HDL
 Function opposite of LDL
 Carries cholesterol from tissues - extract cholesterol from
membrane – change to `cholesteryl esters - LCAT (Lecithin
cholesterol transferase)  bile acids
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