Biochem Lec s IV. Lipids

7/28/2019 Biochem Lec s IV. Lipids

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CHAPTER IV: LIPIDS

DESCRIPTION Gk., lipos, Structurally heterogeneous group of substances of biological origin that are soluble in organic solvents,

but not in water Either

o Hydrophobico Amphipathic

FUNCTIONS1. Energy Source2. Energy reserve3. Insulation4. Protection5. Cell membrane structural components6. Chemical messengers in the human body.7. Vitamins8. Vitamin absorption

CLASSIFICATION ACCORDING TO SOLUBILITY IN NON-POLAR SOLVENTS:

FIGURE 1: Classification of Lipids According to Solubility in Non-polar Solvents

I. FATTY ACIDS Monocarboxylic acids that contain long, unbranched hydrocarbon chains generally 12-26 carbon atoms in

length Building blocks of all saponifiable lipids

o Lipids containing fatty acids: Waxes Fats and oils (triacylglycerols), Glycerophospholipids, Prostaglandins

o Lipids that do not contain fatty acids: steroids Melting point depends on both the length of their hydrocarbon chains and in the degree of unsaturation

(number of double bonds per molecule)

BIOCHEMISTRYLECTURE

Lipids

DATE DEVELOPEDJanuary 2012

DOCUMENT NO.

DEVELOPED BY:Sunshine A. Tayaotao

ISSUED BY:Sunshine A. Tayaotao

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A. SATURATED FATTY ACIDS Carbon-to-carbon chains are single bonds

NAME RATIO CONDENSED FORMULA RCOOH FORMULA SOURCESButyric CH3(CH2)2COOH C3H7COOHCaproic CH3(CH2)4COOH C5H11COOHCaprylic CH3(CH2)6COOH C7H15COOHCapric CH3(CH2)8COOH C9H19COOHLauric (Lt.,Laurus) CH3(CH2)10COOH C11H23COOHMyristic (Myristica, nutmeg genus) CH3(CH2)12COOH C13H27COOHPalmitic (Lt.,Palmitica, palm tree) CH3(CH2)14COOH C15H31COOH

Stearic (Gk., stear, hard fat) CH3(CH2)16COOH C17H35COOHArachidic (Lt., arachis, legume) CH3(CH2)18COOH C19H39COOH

TABLE 1: Saturated Fatty Acids

B. UNSATURATED FATTY ACIDS Carbon chains with one or more cisdouble C=C bonds as shown by the kinks in the fatty acid chains.

a. Monounsaturated fatty acids:NAME RATIO CONDENSED FORMULA RCOOH FORMULA SOURCES

Palmitoleic Acid CH3(CH2)5CH=CH(CH2)7COOH C16H31COOHOleic (Latin oleum, oil) CH3(CH2)7CH=CH(CH2)7COOH C16H29COOH

TABLE 2: Monounsaturated Fatty Acids

b. Polyunsaturated fatty acids Up to 6 double bonds are found in biologically important unsaturated fatty acids

NAME RATIO CONDENSED FORMULA RCOOH FORMULA SOURCESLinoleic Acid* CH3(CH2)4CH=CH(CH2)7COOH C16H31COOHLinolenic Acid* CH3CH2CH=CHCH2CH=

CHCH2CH=CH(CH2)7COOHC17H29COOH

Arachidonic Acid* CH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCH2CH=CH (CH2)3COOH

C19H31COOH

Eicosapentanoic Acid(EPA)

CH3CH2 (CH=CHCH2)5(CH2)2COOH C19H29COOH

Docosahexanoic Acid(DHA)

TABLE 3: Polyunsaturated Fatty Acids

2 Families of Polyunsaturated Fatty Acids (Omega Classification)i. Omega-3 Fatty Acid

Polyunsaturated fatty acid with its endmost double bond three carbons away from itsmethyl end

Sourcesii. Omega-6 Fatty Acids

Polyunsaturated fatty acids with is endmost double bond six carbons away from itsmethyl end

Sources: ESSENTIAL FATTY ACIDS

o Fatty acids needed by the human body and must be obtained from dietary sources because theycannot be synthesized within the body from other substances

o Deficiency:o Linoleic acid, Linoeic acid, Arachidonic acid

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PROPERTY SATURATED FATTY ACID UNSATURATED FATTY ACIDChemical compositionChemical structureCC bonds within the chainChraacterisitic group of HCShape of HC chainPhysical State (RoomTemperature)Melting Point of same ChainLengthRelationship between MeltingPoint and Chain Length

TABLE 4: Similarities and Differences Between Saturated and Unsaturated Fatty Acids

II. GLYCEROL ESTERSA. TRIACYLGLYCEROL (TAG) or TRIGLYCERIDES or NEUTRAL GLYCERIDES

Compound formed by esterification of three fatty acids to glycerolo GLYCEROLo GLYCERIDES

Sources: adipose tissue, butterfat, cream, olive oil, cottonseed oil, corn oil, peanut oil, lard, bacon, suet,chicken fat, fish oil

Esterification:o Carboxylic acid + alcohol ester + water

Types:a. Simple fats/Glycerides

b. Mixed fats/Glycerides

FIGURE 2: Mixed Glyceride

FATS AND OILS Naturally occurring mixtures of tri-esters formed from the reaction between three (3) fatty acid molecules

and a glycerol molecule Formed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids.

BASIS FATS OILSPhysical state at roomtemperatureSourceCompositionMelting point

TABLE 5: Differences between Fats and Oils

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PROPERTIES OF TRIACYLGLYCEROLS: Fats and Oils1. Physical properties

a.b.c.d.

2. Chemical propertiesa. GLYCERIDE FORMATION

FIGURE 5A: Formation of Glycerides

b. HYDROLYSIS Breaking down of ester linkages in the presence of catalyst (acid, base or enzyme)

H+ or enzymes+ 3 H2O 3 fatty acids +

FIGURE 6: Hydrolysis of Glycerides

c. SAPONIFICATION Hydrolysis reaction carried out in an alkaline/basic solution

d. CATALYTIC HYDROGENATION Double bonds in unsaturated fatty acids react with H2 in the presence of a Ni or Pt

catalyst heated at about 200C.

H HNi | |

CH = CH + H2 C C | |H H

FIGURE 7: Catalytic Hydrogenation of Tripalmitolean

e. RANCIDITYi. Hydrolytic rancidityii. Oxidative rancidity

Naturally occurring Synthetic

H2O, H+ H2, Ni

NaOH

FIGURE 8: Reaction Map for Triglycerides

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Glycerol plus Fatty Acids Triglyceride A more saturatedtriglyceride

Glycerol plus Fatty Acid


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B. PHOSPHOLIPIDS/PHOSPHOACYLGLYCEROLS/GLYCEROPHOSPHOLIPIDS Triester of glycerols in which two OH groups are esterified with fatty acids and the third is esterified

with phosphoric acid, which in turn is esterified to an alcohol

FIGURE 9: General Structures of Phospholipids

FIGURE 10: Structures of Different Phosphoacylglyceride

PHOSPHOLIPID NAME OF X FORMULA OF X

Phosphatidic acid

Phosphatidylethanolamine Ethanolamine

Phosphatidylcholine Choline

Phosphatidylserine Serine

Phosphatidylglycerol Glycerol

TABLE 6: Prosthetic Groups for Phosphoacylglyceride

1. Phosphatidylcholines:o Amino alcohol:o Waxy solids that form colloidal suspensions in watero Sources: egg yolks and soy beanso Synthesized by the livero Functions

Component of cell membrane Nutritive supplement: improves memory Emulsifiers: mayonnaise, ice cream and custards Aid in the transport and absorption of fatty acids

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2. PhosphatidylethanolaminesandPhosphatidylserines:o Amino alcohols:o Found in heart and liver tissue and in high concentrations in the braino Important in blood clotting

3. Plasmalogeno Ether linked alkenyl chaino Brain, heart, muscle

III. NON-GLYCERIDE ESTERSA. WAXES Everyday Definition: Chemical Definition: Esters of saturated fatty acids and long-chain alcohols other than glycerol Uses: protective coatings, used in manufacturing candles.

OC O

FIGURE 11: Structural Formula for Waxes

a. Beeswax from honeycomb; chiefly made up of myricyl palmitateb. Cerumenearwax;c. Spermacetifrom the skull of certain whales and dolphins; chiefly made up of cetyl palmitate; used

in candle makingd. Chinesewax found in the secretions of insectse. Carnaubawax found in the cuticle of leavesf. Jojoba wax base of ointments

TABLE 7: Some Typical Waxes

B. SPHINGOLIPIDS Contain a long-chain amino alcohol called sphingosine, rather than glycerol SPHINGOSINE CERAMIDES

FIGURE 10: General Structure of Sphingosine, Ceramide and Sphingolipids

a. Sphingomyelins Sphingolipids in which the esterifying group is phosphoric acid to which choline is

attached Found in all cell membranes

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Long chain alcoholFatty Acid

Alcohol


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Important component of myelin sheath, the protective and insulating coating thatsurrounds the nerves.

Increases the speed of nerve impulse Contains sphingosine

TABLE 8: Types of Sphingomyelins

b. Glycolipids/Glycosphingolipidso Lipids containing a fatty acid, sphingosine, and carbohydrate

i. Glucocerebrosides/Cerebrosides Simplest of carbohydrate containing lipids Monosaccharide forms glycosidic bond with the OH of the ceramide Occur primarily in the brain (7% by dry mass) in myelin sheath of nerves Important in cellular recognition and tissue immunity

ii. Gangliosides More complex carbohydrate heads; up to seven monosaccharides bonded to ceramide Occur in gray matter of the brain as well as in the myelin sheath (i.e., brain, nerves,

spleen) Present in cell membranes where they act as receptors for hormones, viruses and certain

drugsiii. Galactosyl diglyceridesiv. Sulfolipids/Galactolipids

C. STEROIDS Lipids with structures based in a fused-ring system (steroid nucleus) involving three six-membred ring

and five-membered ring Steroid nucleus

o Cylopentanoperhydrophenanthrene (CPPP)o consists of 3 Cyclohexane rings + 1 Cyclopentane ringo No fatty acids

FIGURE 13: Chemical Structures of the Steroid Nucleus and Cholesterol

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SPHINGOLIPID NAME OF X FORMULA OF XCeramide

Sphingomyelin Phosphocholine

GangliosideGM2

Complex oligosaccharide

***GalNac: N-Acetyl D-Galactosamine***Neu5Ac: N-acetylneuraminic acid (sialic acid)

Figure 12: General Structure of Glycolipids


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1. Cholesterolo Most abundant steroid in the human body which is synthesized in the livero Derived from squaleneo Found in cell membranes (up to 25% by mass), nerve tissue and brain tissue (about 10% by dry

mass), and is a main component of gallstoneso Considered elevated if plasma cholesterol exceeds 200 mg/dL.o Functions: starting material for the synthesis of numerous steroid hormones, vitamin D, and bile

saltso Sources: nerve tissue, bile, gall stones, spleen, kidney, brain, sweet breads, liver, egg yolk; whole

milk, butter, fish roe, cheese, ice cream, meats

2. Bile Saltso Emulsifying agents that make dietary lipids soluble in the aqueous environment in the digestive

tracto Product of cholesterol oxidationo Source is bile

3. Steroid Hormoneso ANABOLIC STEROIDS

Derivatives of testosterone Serious ADRs

Increase blood lipid levels very high risk for heart diseases Liver toxicity Male reproduction system alteration Female:

FIGURE 14: Chemical Structures of Some Anabolic Steroids

o HORMONES Produced from cholesterol Chemical messengers produced by ductless glands

o Classes of Steroids:a.Sex hormones

Controls reproduction and secondary sex characteristicsi. Estrogens

Female sex hormones, synthesized in the ovaries and adrenal cortex Example: Functions: Responsible for the development of female secondary characteristics at the onset of

puberty Regulation of menstrual cycle Stimulate development of mammary glands during pregnancy Induce estrus in animals

ii. Androgens Male sex hormones; synthesized in testes and adrenal cortex Example: Functions: Responsible for the development of male secondary characteristics Promote muscle growth

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iii. Progestins Pregnancy hormones; synthesized in ovaries and placenta Example: Functions Prepare lining of the uterus for the implantation of fertilized ovum Suppresses ovulation

b. Adrenocortical hormones Regulate numerous biochemical processes in the body Produced by adrenal glands located on the top of each kidney.

i. Mineralocorticoids Control the balance of Na+ and K+ ions in the body ALDOSTERONE

FIGURE 16: Chemical Structures of Adrenocortical Hormones with their Biological Effects

ii. Glucocorticoids Control glucose metabolism and counteract inflammation CORTISOL

Cortisone4. Eicosanoids

o Oxygenated derivatives of polyunsaturated 20-carbon fatty acidso Precursor:o Gk., eikoso Exert effects in the tissues where they are synthesized

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FIGURE 15: Chemical Structures of Sex

Hormones with their Biological Effects


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o Physiological effects: The inflammatory response, a normal response to tissue damage The production of pain and fever The regulation of blood pressure The induction of blood clotting The control of reproduction functions, such as induction of labor The regulation of sleep/wake cycle

a. Prostaglandins (PG) 20-carbon fatty acid derivatives that contain a cyclopentane ring and oxygen-containing

functional groups PGE soluble in ether; with ketone group at C-9 PGF soluble in phosphate buffer,fosfat(Swedish); hydroxyl group

b. Thromboxanes (TX) 20-carbon fatty acid derivatives that contain a cyclic ether and oxygen-containing

functional groups Produced by blood platelets

c. Leukotrienes (LT) 20-carbon fatty acid derivatives that contain three conjugated double bonds and hydroxyl

groups Found in leukocytes (white blood cells)

FIGURE 17: Formation of Eicosanoids

5. Fat Soluble Vitamins (Vitamin chapter)

IV. COMPLEX LIPIDS1. Aminolipids/Lipoproteins Combined lipids with proteins and phospholipids. Soluble in water because the surface consists of polar lipids. Differ in density, composition, and function. Parts:

o Hydrophobic core o Hydrophilic surface-

Types:a.CHYLOMICRONS

b.VLDL (Very Low Density Lipoprotein)c.IDL ( Intermediate Density Lipoprotein)d.LDL (Low Density Lipoprotein)e.HDL (High Density Lipoprotein)

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FIGURE 20: Formation of Arterial Plaques

CLASSIFICATION OF LIPIDS ON THE BASIS OF COMPOSITION/STRUCTURE

FIGURE 21: Classification of Lipids According to Composition or Structure

1. Simple lipids:a. Triglycerides/Triacylglycerol (TAG)

i. Fats:ii. Oilsare

b. Ester of fatty acids and high MW alcohols other than glyceroli. Waxes

ii. Cholesterylestersiii. VitaminDandAesters

2. Complex lipids:a. Phospholipidsi. Glycerophospholipids/Phosphoglyceridesalcohol

Lecithins Cephalins Plasmalogen

ii. Sphingophospholipids/Phosphosphingosidesalcohol: Sphingomyelins

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b. Glycolipids/Glycosphingolipidsi. Glucocerebrosides

ii. Gangliosidesiii. Galactosyldiglyceridesiv. Sulfolipids/Galactolipids

c. Other complex lipidsi. Aminolipids/Lipoproteins

3. Precursor and derived lipids:a. Fatty acids

i. Saturatedfatty acidsii. Unsaturatedfatty acids

1. Monounsaturated2. Polyunsaturated

iii. Cyclicfattyacidsb. Alcohols

i. Glycerolii. Sterol

iii. Cholesteroliv. Ergosterolv. Calciferol

c. Sphingosine CLASSIFICATION ON THE BASIS OF SAPONIFICATION:

FIGURE 22: Classification of Lipids According to Saponification

CELL MEMBRANES Separate cellular contents from the external environment. Consist of a lipid bilayer made of two rows of phospholipids.

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FLUID MOSAIC MODEL OF CELL MEMBRANES Contains proteins, carbohydrates, and cholesterol. Other substances

o Cholesterolo Glycolipids on surfaceo Proteins embedded in bilayero Proteins on surfaceo Unsaturated fatty acids

o Have proteins and carbohydrates on the surface

FIGURE 23: Diagram of a Cell Membrane

The transport of substances through cell membranes involveso Diffusiono Facilitated transporto Active transport

FIGURE 24: Types of Cell Membrane Transport

DISORDERS OF LIPID METABOLISM (Lipidoses)1. Gaucher's Disease

Caused by a buildup of glucocerebrosides, a product of fat metabolism, in tissues. Most common among Ashkenazi (Eastern European) Jews Leads to an enlarged liver and spleen and a brownish pigmentation of the skin. Accumulation

o Eyeso Bone marrow

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2. Tay-Sachs Disease Caused by a buildup of gangliosides (GM2), products of fat metabolism, in the brain and spleen owing

to lack of the enzyme hexosaminidase A. Most common among families of Eastern European Jewish origin.

3. Fabry's Disease Caused by a buildup of glycolipid, a product of fat metabolism, in tissues. Causes skin growths, pain in the extremities, poor vision, recurrent episodes of fever, and kidney or

heart failure.

4. Niemann-Pick Disease Caused by a buildup of sphingomyelin or cholesterol in the brain, spleen and liver due to a deficiency

of sphingomyelinase The most severe forms tend to occur in Jewish people. The milder forms occur in all ethnic groups.

o Type Ao Type Bo Type C

DISEASE LIPID STORED TYPE ENZYME ABSENTFabrys Gal-gal-glucosylceramide Ganglioside galactosidase

Gauchers Glucosylceramide Cerebroside glucosidaseNiemann-Pick Sphingomyelin Sphingolipid Sphingomyelinase

Tay-Sachs GM2 Ganglioside Ganglioside Hexosaminidase A

TABLE 9: Summary of the Different Lipid Metabolism Disorders

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Biochem Lec s IV. Lipids

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