What are Lipids? A family of compounds that includes

– Triglycerides (fats & oils)– Phospholipids– Sterols (cholesterol)– Waxes– Vitamins– prostaglandins

What are Lipids? Lipids are a structurally heterogeneous group of bioorganic origin that are sparingly soluble, if at

all, in water but are soluble in non polar solvents.` Lipids are composed of C, H, O Diverse group Do not form polymers

– big molecules made of smaller subunits– not a continuing chain

I. FUNCTIONSA. The Functions of Fat in the Body

Energy source esp. for muscles Serves as an energy reserve

1# body fat contains 3500 kcal 30-50# of stored fat

I. FUNCTIONS Major component of cell membranes Nourishes skin & hair Insulates the body from temperature extremes Cushion the vital organs to protect them from shock B. Functions of Fat in Food Provide calories (9 per gram) Provide satiety Carry fat-soluble vitamins & essential fatty acids Contribute aroma & flavor CLASSIFICATION OF LIPIDS SAPONIFIABLE – can be hydrolyzed under alkaline conditions to yield salts of fatty acids NONSAPONIFIABLE – do not undergo hydrolysis reactions under alkaline solutions CLASSIFICATION OF LIPIDS CLASSIFICATION OF LIPIDS SAPONIFIABLE LIPIDS: FATTY ACIDS

FATTY ACIDS are monocarboxylic acids that contain long, unbranched chains generally 12 to 26 carbon atoms in length.

SAPONIFIABLE LIPIDS: FATTY ACIDS SATURATED

FATTY ACIDS UNSATURATED

FATTY ACIDS POLYUNSATURATED

FATTY ACIDS OMEGA-3 AND OMEGA-6

FATTY ACIDS

OMEGA-3 AND OMEGA-6 FATTY ACIDS

IMPORTANT POLYUNSATURATED FATTY ACIDS IMPORTANT POLYUNSATURATED FATTY ACIDS IMPORTANT POLYUNSATURATED FATTY ACIDS ESSENTIAL FATTY ACIDS FATTY ACIDS that can not be synthesized by the body, and should therefore be obtained from

dietary sources. Contributes to proper membrane structure Precursors for the synthesis of arachidonic acid, EPA, DHA

– Linoleic acid– Linolenic acid

ESSENTIAL FATTY ACIDS:DEFICIENCY

Lipid Terminology Triglycerides: the major class of dietary lipids, including fats & oils

– Made up of 3 units known as fatty acids and 1 unit called glycerol (backbone) – Comprise about 95% of lipids in food and the human body

FATS AND OILS: PROPERTIES II. Characteristics of Fats in FoodsA. Hydrogenation

The process of adding hydrogen to unsaturated fat to make it more solid and more resistant to chemical changes such as spoiling

Increasing a fat’s saturation can cause a fat to loose its unsaturated health benefits Trans-Fatty Acids Formed when margarine is processed Hydrogen molecules are on opposite sides of point of unsaturation “Partially hydrogenated vegetable oil” Link between trans fatty acids and heart disease Keep to minimum

SAPONIFIABLE LIPIDS: Phospholipids A lipid consisting of a water-soluble head and a fat-soluble tail Contain phosphorous Component of cell membranes Serve as emulsifiers (allow fats and water to mix and travel in and out of cells into watery

fluid on both sides) PHOSPHOLIPIDS NON GLYCEROL ESTERS:

WAXES A monoester formed from the reaction of a long-chain monohydroxy alcohol with a fatty acid

molecule. NON GLYCEROL ESTER: SPHINGOLIPIDS Sphingolipids are derivatives of the lipid sphingosine, which has a long hydrocarbon tail, and a

polar domain that includes an amino group. NON GLYCEROL ESTER: SPHINGOLIPIDS

Sphingosine may be reversibly phosphorylated to produce the signal moleculeOther derivatives of sphingosine are commonly found as constituents of biological membranes.

A cerebroside is a sphingolipid (ceramide) with a monosaccharide such as glucose or galactose as polar head group.

found in neural tissue membranes, (myelin sheath) ceramide monohexosides most important

a) galactocerebrosideb) glucocerebroside

The amino group of sphingosine can form an amide bond with a fatty acid carboxyl, to yield a ceramide. Sphingomyelin has a phosphocholine or phosphethanolamine head group. Sphingomyelins are common constituent of plasma membranes

a major brain sulfolipid 15% of the lipids in white matter -Sulfogalactocerebroside ceramide oligosaccharides contain 2 or more sugar molecules

galactose glucose N-acetylgalactosamineattached to ceramide

found in serum, the spleen, the liver and erythrocytesEx. Lactosylceramide

erythrocyte membranes A ganglioside is a ceramide with a polarhead group that is a complex oligosaccharide, including

the acidic sugar derivative sialic acid.Nature

found in high concentration in ganglion cells of the CNS and low concentration in the membrane of most cells

glycosphingolipids, with 1 or more neuraminic acid residues) N-acetyl derivative(N-acetylneuraminic acid, NANA which is sialic acid

b. Nomenclature1) G-denote a ganglioside2) M, D, T, or Q-subscripts which indicate, respectively, mono, di-, tri-, or quatro-sialic acid

contents3) numerical subscripts-arbitrary assignment based on the chromatographic migration of

gangliosides inherited genetic disorders referred to as lipid storage diseases there is deficiency of an enzyme that is involved in the normal catabolism of a particular

sphingolipid accumulation of that lipid to harmful levels.

NONSAPONIFIABLE LIPIDS:Cholesterol

Found only in animal products Also made & used in the body:

– Structure of cell membranes– Used to make bile for digestion

Bile: a mixture of compounds, made by the liver, stored in the gallbladder, & secreted into the small intestine

Emulsifies lipids to prepare them for enzymatic digestion & helps transport them into the intestinal wall cells

Cholesterol

Used to make the sex hormones estrogen & testosterone

Made into vitamin D with the help of sunlight Deposited in the artery walls leading to plaque buildup & heart disease How the Body Handles FatA. DigestionB. EmulsificationC. Absorption Fat in the DietA. Food Guide Pyramid

3 groups traditionally account for nine-tenths of the fat in the U.S. diet Fats, oils & sweets group Meat, poultry, fish, dry beans, eggs & nut group Milk, yogurt & cheese group Most of the fat in our diets comes from animal products

Fat Substitutes Carbohydrate-based

– Help retain moisture to maintain the juiciness or creaminess that is lost with fat reduction

– Carrageenan, fruit purees, gelatin, gums, starches & products made from fiber Protein-based

– Proteins are cooked & blended to form tiny round particles that trap water to maintain the mouth feel of fat

– Whey protein concentrate (Dairy-Lo), or milk & egg white protein (Simplesse) Fat Substitutes Fat-based

– Are either only partially digestible or completely undigestible to prevent absorption of fat

– Caprenin (substitute for cocoa butter in candy), Salatrim (found in low fat baking chips), and olestra (often found in fat free potato chips)

LIPID PEROXIDATION A chain reaction initiated by “free” radicals which provides a continuous supply of other “free”

radicals formed from unsaturated FA In the living cells, lipids undergo oxidation to produce peroxidases and free radicals which can

damage the tissues Cause: inflammatory diseasesageing atherosclerosis, cancer LIPID PEROXIDATION LIPID PEROXIDATION To control and reduce lipid peroxidation both in humans and in nature…

are used LIPID PEROXIDATION Small amounts of vitamins A, D, E and K are needed to maintain good health. Foods that contain these vitamins will not lose them when cooked. The body does not need these every day and stores them in the liver when not used. Most people do not need vitamin supplements. Megadoses of vitamins A, D, E or K can be toxic and lead to health problems. Vitamin A, also called retinol, has many functions in the body.

– helps the eyes adjust to light changes– plays an important role in bone growth, tooth development, reproduction, cell division and

gene expression.

– the skin, eyes and mucous membranes of the mouth, nose, throat and lungs depend on vitamin A to remain moist.

Vitamin D, also known as cholecalciferol (D3), or ergocalciferol (D2), plays a critical role in the body’s use of calcium and phosphorous. It increases the amount of calcium absorbed from the small intestine and helps form and maintain bones. Children especially need adequate amounts of vitamin D to develop strong bones and healthy teeth.

Vitamin E, also known as α - tocopherol, acts as an antioxidant, protecting vitamins A and C, red blood cells and essential fatty acids from destruction.

Vitamin K, also known as quinones, produced by the bacteria in the intestines plays an essential role in normal blood clotting and helps promote bone health. 

Carbohydrates General characteristics the term carbohydrate is derived from the french: hydrate de carbone compounds composed of C, H, and O C(H2O)n when n = 5 then C5H10O5

not all carbohydrates have this empirical formula: deoxysugars, aminosugars carbohydrates are the most abundant compounds found in nature (cellulose: 100 billion tons

annually) General characteristics Most carbohydrates are found naturally in bound form rather than as simple sugars

Polysaccharides (starch, cellulose, inulin, gums) Glycoproteins and proteoglycans (hormones, blood group substances, antibodies) Glycolipids (cerebrosides, gangliosides) Glycosides Mucopolysaccharides (hyaluronic acid) Nucleic acids

OccurencesGreen plants produce carbohydrates via photosynthesis.Plants have two main uses for the carbohydrates they produce.

cellulose – structural elements starch – energy reserves Functions sources of energy intermediates in the biosynthesis of other basic biochemical entities (fats and proteins) associated with other entities such as glycosides, vitamins and antibiotics) form structural tissues in plants and in microorganisms (cellulose, lignin, murein) participate in biological transport, cell-cell recognition, activation of growth factors, modulation of

the immune system Classification of carbohydrates Monosaccharides (monoses or glycoses)

Trioses, tetroses, pentoses, hexoses Oligosaccharides

Di, tri, tetra, penta, up to 9 or 10 Most important are the disaccharides

Polysaccharides or glycans Homopolysaccharides Heteropolysaccharides Complex carbohydrates

Monosaccharides also known as simple sugars

classified by 1. the number of carbons 2. whether aldoses or ketoses

most (99%) are straight chain compounds D-glyceraldehyde is the simplest of the aldoses (aldotriose) all other sugars have the ending ose (glucose, galactose, ribose, lactose, etc…) Aldoses and Hexoses Aldose sugars Ketose sugars D and L Sugars Biologically Important Monosaccharides Biologically Important Monosaccharide: Glucose Cyclic Form of Glucose Biologically Important Monosaccharides: Haworth form Cyclic Form of Fructose Anomers Mutarotation Epimerization Non Reducing Sugars Enantiomers and epimers Properties Differences in structures of sugars are responsible for variations in properties Physical

Crystalline form; solubility; rotatory power Chemical

Reactions (oxidations, reductions, condensations) Physiological

Nutritive value (human, bacterial); sweetness; absorption Optical isomerism A property exhibited by any compound whose mirror images are non-superimposable Asymmetric compounds rotate plane polarized light Instruments used to measure degree of rotation of plane-polarized light of enantiomeric

compounds are called polarimeter. Dextrorotatory – a compound that rotates plane-polarized light in a clockwise direction Levorotatory – a compound that rotates plane-polarized light in a counterclockwise direction Reactions of monosaccharides Carbonyl reactions:

Osazone formation Cyanohydrin reaction Reduction Oxidation Action of base Action of acid Ring chain tautomerism

Alcohol reactions Glycoside formation Ether formation Ester formation

Formation of osazones once used for the identification of sugars

consists of reacting the monosaccharide with phenylhydrazine a crystalline compound with a sharp melting point will be obtained D-fructose and D-mannose give the same osazone as D-glucose seldom used for identification; we now use HPLC or mass spectrometry Oxidation reactions Aldoses may be oxidized to 3 types of acids

Aldonic acids : aldehyde group is converted to a carboxyl group ( glucose – gluconic acid) Uronic acids : aldehyde is left intact and primary alcohol at the other end is oxidized to

COOH Glucose --- glucuronic acid Galactose --- galacturonic acid

Saccharic acids (glycaric acids) – oxidation at both ends of monosaccharide) Glucose ---- saccharic acid Galactose --- mucic acid Mannose --- mannaric acid

Oxidation by Bromine Oxidation by Nitric acid Oxidation by Tollen’s Reagent Glucose oxidase glucose oxidase converts glucose to gluconic acid and hydrogen peroxide when the reaction is performed in the presence of peroxidase and o-dianisidine a yellow color is

formed this forms the basis for the measurement of urinary and blood glucose

Testape, Clinistix, Diastix (urinary glucose) Dextrostix (venous glucose)

Reduction either done catalytically (hydrogen and a catalyst) or enzymatically the resultant product is a polyol or sugar alcohol (alditol) glucose form sorbitol (glucitol) mannose forms mannitol fructose forms a mixture of mannitol and sorbitol glyceraldehyde gives glycerol Sugar alcohols are very useful intermediates Mannitol is used as an osmotic diuretic Glycerol is used as a humectant and can be nitrated to nitroglycerin Sorbitol can be dehydrated to tetrahydropyrans and tetrahydrofuran compounds (sorbitans) Sorbitans are converted to detergents known as spans and tweens (used in emulsification

procedures) Sorbitol can also be dehydrated to 1,4,3,6-dianhydro-D-sorbitol (isosorbide) which is nitrated to

ISDN and ISMN (both used in treatment of angina) Formation of spans and tweens Action of strong acids on monosaccharides monosaccharides are normally stable to dilute acids, but are dehydrated by strong acids D-ribose when heated with concentrated HCl yields furfural (commercial route for the production

of THF (tetrahydrofuran) D-glucose under the same conditions yields 5-hydroxymethyl furfural Action of base on sugars Sugars are weak acids and can form salts at high pH A 1,2-enediol salt is formed as the result This allows the interconversion of D-mannose, D-fructose and D-glucose

The reaction is known as the Lobry de Bruyn-Alberta von Eckenstein reaction Action of base on sugars enediols obtained by the action of base are quite susceptible to oxidation when heated in the

presence of an oxidizing agent copper sulfate is frequently used as the oxidizing agent and a red preciptate of Cu2O is obtained sugars which give this reaction are known as reducing sugars Fehling’s solution : KOH or NaOH and CuSO4

Benedict’s solution: Na2CO3 and CuSO4

Clinitest tablets are used to detect urinary glucose in diabetics Glucose measurement methods Most methods are enzymatic methods

3 enzyme systems are currently used to measure glucose: Glucose oxidase Glucose dehydrogenase Hexokinase

These reactions produce either a product that can be measured photometrically or an electrical current that is proportional to the initial glucose concentration

Glucose dehydrogenase methods Glucose oxidase methods:

colorimetric method Glucose oxidase methods:

electronic sensing method Special monosaccharides: deoxy sugars These are monosaccharides which lack one or more hydroxyl groups on the molecule one quite ubiquitous deoxy sugar is 2’-deoxy ribose which is the sugar found in DNA 6-deoxy-L-mannose (L-rhamnose) is used as a fermentative reagent in bacteriology Examples of glycosides Disaccharides Disaccharides Most common are the disaccharides

Sucrose, lactose, and maltose Maltose hydrolyzes to 2 molecules of D-glucose Lactose hydrolyzes to a molecule of glucose and a molecule of galactose Sucrose hydrolyzes to a molecule of glucose and a molecule of fructose

Disaccharides Sucrose a-D-glucopyranosido-b-D-fructofuranoside b-D-fructofuranosido-a-D-glucopyranoside also known as table sugar commercially obtained from sugar cane or sugar beet hydrolysis yield glucose and fructose (invert sugar) ( sucrose: +66.5o ; glucose +52.5o; fructose –

92o) used pharmaceutically to make syrups, troches Disaccharides Maltose 2-glucose molecules joined via a(1,4) linkage known as malt sugar produced by the partial hydrolysis of starch (either salivary amylase or pancreatic amylase) used as a nutrient (malt extract; Hordeum vulgare); as a sweetener and as a fermentative reagent Lactose

b-D-galactose joined to a-D-glucose via b (1,4) linkage milk contains the a and b-anomers in a 2:3 ratio b-lactose is sweeter and more soluble than ordinary a- lactose used in infant formulations, medium for penicillin production and as a diluent in pharmaceuticals Lactulose galactose-b-(1,4)-fructose a semi-synthetic disaccharide (not naturally occurring) not absorbed in the GI tract used either as a laxative (Chronulac) or in the management of portal systemic encephalopathy

(Cephulac) metabolized in distal ileum and colon by bacteria to lactic acid, formic acid and acetic acid

(remove ammonia) Oligosaccharides Trisaccharide: raffinose (glucose, galactose and fructose) Tetrasaccharide: stachyose (2 galactoses, glucose and fructose) Pentasaccharide: verbascose (3 galactoses, glucose and fructose) Hexasaccharide: ajugose (4 galactoses, glucose and fructose) Polysaccharides or glycans homoglycans (starch, cellulose, glycogen, inulin) heteroglycans (gums, mucopolysaccharides) characteristics:

polymers (MW from 200,000) White and amorphous products (glassy) not sweet not reducing; do not give the typical aldose or ketose reactions) form colloidal solutions or suspensions

Starch most common storage polysaccharide in plants composed of 10 – 30% a-amylose and 70-90% amylopectin depending on the source the chains are of varying length, having molecular weights from several thousands to half a

million Amylopectin Cellulose Polymer of b-D-glucose attached by b(1,4) linkages Yields glucose upon complete hydrolysis Partial hydrolysis yields cellobiose Most abundant of all carbohydrates

Cotton flax: 97-99% cellulose Wood: ~ 50% cellulose

Gives no color with iodine Held together with lignin in woody plant tissues Products obtained from cellulose Microcrystalline cellulose : used as binder-disintegrant in tablets Methylcellulose: suspending agent and bulk laxative Oxidized cellulose: hemostat Sodium carboxymethyl cellulose: laxative Cellulose acetate: rayon; photographic film; plastics Cellulose acetate phthalate: enteric coating Nitrocellulose: explosives; collodion (pyroxylin) Glycogen

also known as animal starch stored in muscle and liver present in cells as granules (high MW) contains both a(1,4) links and a(1,6) branches at every 8 to 12 glucose unit complete hydrolysis yields glucose glycogen and iodine gives a red-violet color hydrolyzed by both a and b-amylases and by glycogen phosphorylase Glycogen Inulin b-(1,2) linked fructofuranoses linear only; no branching lower molecular weight than starch colors yellow with iodine hydrolysis yields fructose sources include onions, garlic, dandelions and jerusalem artichokes used as diagnostic agent for the evaluation of glomerular filtration rate (renal function test) Chitin chitin is the second most abundant carbohydrate polymer present in the cell wall of fungi and in the exoskeletons of crustaceans, insects and spiders chitin is used commercially in coatings (extends the shelf life of fruits and meats) Dextrans products of the reaction of glucose and the enzyme transglucosidase from Leuconostoc

mesenteroides contains a (1,4), a (1,6) and a (1,3) linkages MW: 40,000; 70,000; 75,000 used as plasma extenders (treatment of shock) also used as molecular sieves to separate proteins and other large molecules (gel filtration

chromatography) components of dental plaques Dextrins produced by the partial hydrolysis of starch along with maltose and glucose dextrins are often referred to as either amylodextrins, erythrodextrins or achrodextrins used as mucilages (glues) also used in infant formulas (prevent the curdling of milk in baby’s stomach) Glycosaminoglycans they are the polysaccharide chains of proteoglycans they are linked to the protein core via a serine or threonine (O-linked) the chains are linear (unbranched) the glycosaminoglycan chains are long (over 100 monosaccharides) they are composed of repeating disaccharides Hyaluronic acid derivatives several products are used in the management of osteoarthritis symptoms

Hyalagan and Synvisc others are used as ophthalmic surgical adjuncts in cataract extractions, intraocular lens

implantation, corneal transplant and retinal attachment surgery (Healon, Amvisc, AMO Vitrax) Pectins pectins are heteropolysaccharides found in the pulp of fruits (citrus, apples) on hydrolysis pectins yield galacturonic acid, galactose, arabinose, methanol and acetic acid pectins are composed of galactans and arabans used as gelling agents (to make jellies)

Gums widely used in the food and pharmaceutical industry used as: suspending agents, gelling agents, thickening agents, emulsifiers, foam stabilizers,

crystallization inhibitors, adhesives, binding agents agar, tragacanth, karaya, carrageenan, guar gum, gum arabic (acacia), furcellaran, sodium alginate,

locust bean gum Bacterial cell wall provide strength and rigidity for the organism consists of a polypeptide-polysaccharide known as peptidoglycan or murein determines the Gram staining characteristic of the bacteria Mycobacterial cell wall Glycosylated proteins Usually done as a post-translational process Proteins can contain either O-linked oligosaccharides or N-linked oligosaccharides GLYCOLIPIDS Cerebrosides

One sugar molecule Galactocerebroside – in neuronal membranes Glucocerebrosides – elsewhere in the body

Sulfatides or sulfogalactocerebrosides A sulfuric acid ester of galactocerebroside

Globosides: ceramide oligosaccharides Lactosylceramide

2 sugars ( eg. lactose) Gangliosides

Have a more complex oligosaccharide attached Biological functions: cell-cell recognition; receptors for hormones

glycolipids Gangliosides complex glycosphingolipids that consist of a ceramide backbone with 3 or more sugars

esterified,one of these being a sialic acid such as N-acetylneuraminic acid common gangliosides: GM1, GM2, GM3, GD1a, GD1b, GT1a, GT1b, Gq1b

Ganglioside nomenclature letter G refers to the name ganglioside the subscripts M, D, T and Q indicate mono-, di-, tri, and quatra(tetra)-sialic-containing

gangliosides the numerical subscripts 1, 2, and 3 designate the carbohydrate sequence attached to ceramide Ganglioside nomenclature Numerical subscripts:

1. Gal-GalNAc-Gal-Glc-ceramide 2. GalNAc-Gal-Glc-ceramide 3. Gal-Glc-ceramide

Lipid storage diseases also known as sphingolipidoses genetically acquired due to the deficiency or absence of a catabolic enzyme examples:

Tay Sachs disease Gaucher’s disease Niemann-Pick disease

Fabry’s disease