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BCM 3000PRINCIPLES OF BIOCHEMISTRY

(Semester 1 -2011/12)

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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.

LIPID

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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

LIPID

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Any natural compound which is insoluble or nearly insoluble in water but soluble in non-polar solvents –

a. Chloroform

b. CS2

c. Ether

d. warm or

e. hot ethanol

General Definition

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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

FUNCTIONSLipids are widely distributed in both animal and plant systems and perform a wide variety of functions

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1. SIMPLE LIPIDS

Fatty acid esters(Acid + alcohol ester)

2. COMPPOUND LIPID

Fatty acid + alcohol + OTHER COMPOUNDS

CLASSIFICATION

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LIPID COMPONENTS

Acyglycerols (Glycerol + Fatty acids) =

Waxes Alcohol + fatty acids

SIMPLE LIPIDS

Esters

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4 types of Compound lipid

i. Phosphoglycerides

ii. Sphingolipids

iii. Cerebrosides

iv. Gangliosides

COMPOUND LIPIDS

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LIPID COMPONENTS

i PhosphoglyceridesGlycerol + Fatty acid +HPO4

2- + satu OHR

ii Sphingolipids Sphingosine + Fatty acid + HPO4

2- + Choline

iii Cerebrosides Sphingosine +Fatty acid + Simple sugar

iv GangliosidesSphingosine + Fatty acid+ 2-6 Simple sugar (Including sialic acid)

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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● 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

FATTY ACIDS

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Octadenic acid

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2 TYPES

1. Saturated Fatty acids

2. Unsaturated Fatty acids

FATTY ACIDS

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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.

Structure of Fatty Acids - Saturated

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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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● 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)

Structure of Fatty Acids - Unsaturated

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● 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

Unsaturated fatty acids

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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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● 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

Oils

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CIS TRANS

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● 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.

Making margarine

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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

SIMPLE LIPIDS

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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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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.

FUNCTIONS IN ANIMALS

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● Also an ester - alcohol & fatty acid = very long hydrocarbon chain – commercial application

● hairs, skin, leaves, fruits

WAXES

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Asid Oleic

WAXES

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1. Hydrogenation

CHEMICAL CHARACTERISTICS OF TRYACYLGLYCEROL (Reactions of Triacylglycerol)

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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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Other halides - Iodine(I2), Chlorides (Cl2)

2. Halogenation – Addition of halogens

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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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(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

3. Hydrolysis

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● 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

SAPONIFICATION

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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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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

HOW DOES A DETERGENT WORK ??

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Grease

Water

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Head -Polar

(hidrofilik)

Ekor-Tak polar(Hidrofobi

k)

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Carboxylic acids

(ii). Acid Hydrolysis

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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)

4. RANCIDITY

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Phosphoglycerides = Phosphoglyceroli.e. they are derived from glycerol

Fatty acids

Phosphate group

Glycerol

Phosphoglycerides

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Phosphoglycerol = Phosphoglyceride

Glycerol @ other alcohols

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Glycerol (Trihydroxyglycero

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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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● 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

SPHINGOLIPID

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CHCH(CH2)12CH3

CHOH CH NH2

CH2OH

H2C OH H2COH H2C OH

Sphingosine Glycerol

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

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● 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

SPHINGOLIPID

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CERAMIDE

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Phosphate

Choline

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● 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

GLYCOLIPID

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● A heterogeneous group ● Derived from fatty acids ● steroids, prostaglandin, leukotriene, carotenoids,

vitamin

STEROID

All organisms – similar basic structure – fused ring=

perhydrocylopentanophenanthrene

DERIVED LIPIDS

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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

STEROL

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Hydrocarbon chain at C17

OH at C3

CHOLESTEROL

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● 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

TERPENE

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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

TERPENE

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TERPENE

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TERPENE

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TERPENE

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BCM 3000PRINCIPLES OF BIOCHEMISTRY

(Semester 1 -2011/12)

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● 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

LIPID BEHAVIOUR IN WATER

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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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MONOLAYERMICELLES

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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

BilayerVesicles

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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 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

BILE ACID AND BILE SALTS

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Glycine Taurine

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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

LIPOPROTEIN

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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

110CHYLOMICRON

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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

LDL, CHOLESTEROL & ATHEROSCLEROSIS

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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