Di- and polysaccharides.

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Lecture ? 15

• Di- and polysaccharides.
• Terpenes.

Ass. Medvid I.I. Ass. Burmas N.I
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Outline

• Oligosaccharides.
• The following functions of carbohydrates in
  humans.
• 3.Classification of disaccharides
• maltose
• cellobiose
• lactose
• saccharose.
• 4. Polysaccharides (glucanes).
• a) Homopolysaccharides
• - Structure, composition and properties of
  cellulose.
• - Structure, composition and properties of
  starch.
• - Glycogen, dextranes, inuline, pectin compounds,
  chitin.
• b) Heteropolysaccharides.
• 5. Glycoconjugates.

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• 6. Lipids.
• 7. Chemical properties of fats
• 8. Phospholipids. Waxes.
• 9. Nonsaponifiable lipids.
• 10. Terpenes and terpenoids. Terpene
  biosynthesis.
• 11. Classification of terpenes.
• 12. Carotenoids.
• 13. Steroids.
• 14. Properties of cholesterol. Biosynthesis of
  cholesterol.
• 15. Vitamins.
• 16. Water-soluble vitamins.
• 17.Water insoluble (lipid-soluble) vitamins.

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• Oligosaccharides.
• The term oligosaccharide is often used for
  carbohydrates that consist of between two and ten
  monosaccharide units. Oligosaccharides are
  carbohydrates that contain from two to ten
  monosaccharide units.
• Disaccharides are the most common type of
  oligosaccharide. Disaccharides are carbohydrates
  composed of two monosaccharide units covalently
  bonded to each other. Like monosaccharides,
  disaccharides are crystalline, water-soluble
  substances. Saccharose (table sugar) and lactose
  (milk sugar) are disaccharides. Within the human
  body, oligosaccharides are often found associated
  with proteins and lipids in complexes that have
  both structural and regulatory functions. Free
  oligosaccharides, other than disaccharides, are
  seldom encountered in biological systems
• Complete hydrolysis of an oligosaccharide
  produces monosaccharides. Upon hydrolysis, ?
  disaccharide produces two monosaccharides, ?
  trisaccharide three monosaccharides, ?
  hexasaccharide six monosaccharides, and so on.

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• Carbohydrates are the most abundant class of
  bioorganic molecules on planet Earth. Although
  their abundance in the human body is relatively
  low, carbohydrates constitute about 75 by mass
  of dry plant materials.
• Green (chlorophyll-containing) plants produce
  carbohydrates via photosynthesis. In this
  process, carbon dioxide from the air and water
  from the soil are the reactants, and sunlight
  absorbed by chlorophyll is the energy source.
• Plants have two main uses for the carbohydrates
  they produce. In the form of cellulose,
  carbohydrates serve as structural elements, and
  in the form of starch, they provide energy
  reserves for the plants.
• Dietary intake of plant materials is the major
  carbohydrate source for humans and animals. The
  average human diet should ideally be about
  two-thirds carbohydrate by mass.

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• 2. The following functions of carbohydrates in
  humans.
• Carbohydrates have the following functions in
  humans
• 1. Carbohydrate oxidation provides energy
• 2. Carbohydrate storage, in the form of glycogen,
  provides ? short- term energy reserve.
• 3. Carbohydrates supply carbon atoms for the
  synthesis of other biochemical substances
  (proteins, lipids, and nucleic acids).
• 4. Carbohydrates form part of the structural
  framework of DNA and RNA molecules.
• 5. Carbohydrate "markers" on cell surfaces play
  key roles in cell -cell recognition processes.

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• 3.Classification of disaccharides
• (1) N?n-reducing disaccharides. In these
  disaccharides the two hexose units are linked
  together through their reducing (i ?. aldehydic
  or ketonic) groups which is , in aldoses
  and , in ketoses. Now in such cases since
  the reducing groups of both hexoses are lost, the
  resulting compound (disaccharide) will be
  non-reducing. Hence such disaccharides do not
  form osazone do not show mutarotation and do not
  react with reagents like Felings solution,
  Tollens reagent, etc. Important example of
  non-reducing disaccharides is saccharose.
• (2) Reducing disaccharides. In these
  disaccharides, one hexose unit is linked through
  its reducing carbon to the non-reducing carbon
  (C4 or ?6) of the other Now since the reducing
  group of one of the hexoses is not involved, the
  resulting disaccharide will be ? reducing sugar.
  Maltose and lactose are examples of reducing
  disaccharides.

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• As mentioned earlier, disaccharides are those
  sugars which on hydrolysis give two moles of
  monosaccharides general these are sweet-testing
  crystalline, water-soluble substances, easily
  hydrolysed by enzymes and dilute mineral acids.
  The common disaccharides have the general formula
  C12H22O11 which during hydrolysis take one
  molecule of water to form two hexoses.
• Disaccharides are formed by intermolecular
  dehydration between two monosaccharide molecules,
  e.g. In the formation of disaccharides, at least
  one monosaccharide unit is linked to the other
  through the glycosidic carbon atom. In other
  words we can say that in the formation of
  disaccharide, reducing property of at least one
  hexose unit is lost. Hence disaccharides may be
  considered as glycosides in which both components
  of the molecules are sugars. Disaccharides may
  exist in two types, namely non-reducing and
  reducing depending on the fact that ?1 of one
  hexose is linked to the carbonyl carbon at other
  carbon atom of other hexose. Weak oxidizing
  agents, such as Tollens, Feling's, and Benedict's
  solutions, oxidize the carbonyl group end of ?
  monosaccharide to give an -onic acid.

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• Disaccharides. ? monosaccharide that has cyclic
  forms (hemiacetal or hemiketal) can react with an
  alcoho1 to form ? glycoside (acetal or ketal).
  This same type of reaction can be used to produce
  ? disaccharide, ? carbohydrate in which two
  monosaccharides are bonded together. In
  disaccharide formation, one of the monosaccharide
  reactants functions as ? hemiacetal or hemiketal,
  and the other functions as an alcohol.
• Monosaccharide monosaccharide disaccharide
  ?2O
• The bond that links the two monosaccharides of ?
  disaccharide together is called ? glycosidic
  linkage. ? glycosidic linkage is the
  carbon-oxygen-carbon bond that joins the two
  components of ? glycoside together. The bond that
  links the two monosaccharides of ? disaccharide
  together is called ? glycosidic linkage. We now
  examine the structures and properties of four
  important disaccharides maltose, cellobiose,
  lactose, and saccharose. As we consider details
  of the structures of these compounds, we will
  find that the configuration (a or ß) at carbon-1
  of the reacting monosaccharides is often of prime
  importance.

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• Maltose, often called malt sugar, is produced
  by breaking down the polysaccharide starch, as
  takes place in plants when seeds germinate and in
  human beings during starch digestion. It is ?
  common ingredient in baby foods and is found in
  malted milk. Malt (germinated barley that has
  been baked and ground) contains maltose hence
  the name malt sugar. Structurally, maltose is
  made up of two D-glucopyranose units, one of
  which must be ?-D-glucose. The formation of
  maltose from two glucose molecules is as follows
• ?-D-Glucose ?-D-Glucose
  ?-(1-4)-linkage

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So, a-maltose can be named as 4-O-(a-D-glucopyrano
sido)-a-D-glucopyranose, ß-maltose
4-O-(a-D-glucopyranosido)-ß-D-glucopyranose.
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• The glycosidic linkage between the two glucose
  units is called an ?(1 - 4) linkage. The two
  ??-groups that form the linkage are attached,
  respectively, to carbon-1 of the first glucose
  unit (in an a configuration) and to carbon-4 of
  the second. Maltose is ? reducing sugar, because
  the glucose unit on the right has ? hemiacetal
  carbon atom (?-1).Thus this glucose unit can open
  and close it is in equilibrium with its
  open-chain aldehyde form. This means there are
  actually three forms of the maltose molecule
  ?-maltose, ?-maltose, and the open-chain form. In
  the solid state, the ?-form is dominant. The most
  important chemical reaction of maltose is
  hydrolysis. Hydrolysis of D-maltose, whether in ?
  laboratory flask or in ? living organism,
  produces two molecules of D-glucose.

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• Cellobiose is produced as an intermediate in
  the hydrolysis of the polysaccharide cellulose.
  Like maltose, cellobiose contains two D-glucose
  monosaccharide units. It differs from maltose in
  one of D-glucose units - the one functioning as ?
  hemiacetal - must have ? ?-configuration instead
  of the ? configuration of maltose. This change in
  configuration gives ? ?(1-4) glycosidic linkage.

?-D-Glucose
?(1-4)-linkage
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a-cellobiose can be named as 4-O-(ß-D-glucopyranos
ido)-a-D-glucopyranose, ß-cellobiose
4-O-(ß-D-glucopyranosido)-ß-D-glucopyranose.
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• Like maltose, cellobiose is a reducing sugar,
  has three isomeric forms in aqueous solution, and
  upon hydrolysis produces two D-glucose molecules.
  Despite these similarities, maltose and
  cellobiose have different biological behaviors.
  These differences are related to the
  stereochemistry of their glycosidic linkages.
  Maltase, the enzyme that breaks the
  glucose-glucose ?(1-4) linkage present in
  maltose, is found both in the human body and in
  yeast. Consequently, maltose is digested easily
  by humans and is readily fermented by yeast. Both
  the human body and yeast lack the enzyme
  cellobiase needed to break the glucose - glucose
  ?(1-4) linkage of cellobiose. Thus cellobiose
  cannot be digested by humans or fermented by
  yeast. In maltose and cellobiose, the two units
  of the disaccharide are identical - two glucose
  units in each case.
• Maltose and cellobiose have different
  arrangement in space. In maltose molecule
  a-glycosidic linkage has axial arrangement, in
  cellobiose molecule ß-glycosidic linkage
  equatorial. Its cases club-similar structure of
  amylose and linear structure of cellulose.

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• Lactose includes ?-D-galactopyranose unit and ?
  D-glucopyranose unit joined by ?-(1-4) glycosidic
  linkage

?-D-galactose ?-D-Glucose
?(1-4)-linkage
The glucose hemiacetal center is active when
galactose bonds to glucose in the formation of
lactose, so lactose is ? reducing sugar (the
glucose ring can open to give an
aldehyde).Lactose is the major sugar found in
milk. This accounts for its common name, milk
sugar. Enzymes in animal mammary glands take
glucose from the bloodstream and synthesize
lactose in ? four-step process. Epimerization of
glucose yields galactose, and then the ?(1-4)
linkage forms between ? galactose and ? glucose
unit. Lactose is an important ingredient in
commercially produced infant formulas that are
designed to simulate mother' s milk. Souring of
milk is caused by the conversion of lactose to
lactic acid by bacteria in the milk.
Pasteurization of milk is ? quick-heating process
that kills most of the bacteria and retards the
souring process. Lactose can be hydrolyzed by
acid or by the enzyme lactase, forming an
equimolar mixture of galactose and glucose. In
the human body, the galactose produced in such
way is then converted to glucose by other
enzymes. The genetic condition lactose
intolerance, an inability of the human digestive
system to hydrolyze lactose.
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a-lactose can be named as 4-O-(ß-D-galactopyranosi
do)-a-D-glucopyranose, ß-lactose
4-O-(ß-D-galactopyranosido)-ß-D-glucopyranose. Arr
angement in space is similar to cellobiose
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• Saccharose, common table sugar, is the most
  abundant of all disaccharides and occurs
  throughout the plant kingdom. It is produced
  commercially from the juice of sugar cane and
  sugar beets. Sugar cane contains up to 20 by
  mass saccharose, and sugar beets contain up to 17
  by mass saccharose. The two monosaccharide
  units present in ?-D-saccharose molecule are
  ?-D-glucose in form of ?-D-glucopyranose and
  ?-D-fructose in form of ?-D-fructofuranose. The
  glycosidic linkage is not ? (1-4) linkage, as was
  in case with maltose, cellobiose, and lactose. It
  is instead an ?,?(1 - 2) glycosidic linkage. The
  ??-group on carbon-2 of D-fructose (the hemiketal
  carbon) reacts with the ??-group on carbon-l of
  D-glucose (the hemiacetal carbon).

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Saccharose can be named as 2-O-(a-D-glucopyranosid
o)-ß-D-fructofuranose.
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• Saccharose, unlike maltose, cellobiose, and
  lactose, is ? non-reducing sugar. No helmiacetal
  or hemiketal center is present in the molecule,
  because the glycosidic linkage involves the
  reducing ends of both monosaccharides.
  Saccharose, in the solid state and in solution,
  exists in only one form - there are no ? and ?
  isomers, and an open-chain form is not possible.
  Saccharase, the enzyme needed to break the ?,?(1
  - 2) linkage in saccharose, is present in the
  human body. Hence saccharose is an easily
  digested substance.

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• Saccharose hydrolysis (digestion) produces an
  equimolar mixture of glucose and fructose called
  invert sugar. When saccharose is cooked with
  acid-containing foods such as fruits or berries,
  partial hydrolysis takes place, forming some
  invert sugar. Jams and jellies prepared in this
  manner are actually sweeter than the pure
  saccharose added to the original mixture, because
  one-to-one mixtures of glucose and fructose taste
  sweeter than saccharose.
• Saccharose is dextrorotatory. On hydrolysis it
  gives one molecule of glucose and one molecule of
  fructose. Now since fructose is more strongly
  laevorotatory than the dextrorotatory property of
  glucose, the mixture (product) after hydrolysis
  will be laevorotatory. This reaction is also as
  inversion of sugar because the dextrorotatory
  case sugar is converted into laevorotatory
  product due to hydrolysis. The mixture of glucose
  and fructose is called invert sugar.

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dextrorotatory
laevorotatory
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• 4. Polysaccharides (glucanes)
• ? polysaccharides (glucanes) contains many
  monosaccharide units bonded to each other by
  glycosidic linkages. The number of monosaccharide
  units in polysaccharides varies from ? few
  hundred to hundreds of thousands. Polysaccharides
  are polymers. In some, the monosaccharides are
  bonded together in ? linear (unbranched) chain.
  In others, there is extensive branching of the
  chains. Unlike monosaccharides and most
  disaccharides, polysaccharides are not sweet and
  do not give positive reaction with Tollens,
  Benedicts, and Felings solutions. They have
  limited water solubility because of their size.
  However, the ??-groups present in molecule can
  individually become hydrated by water molecules.
  The result is usually ? thick colloidal
  suspension of the polysaccharide in water.
  Polysaccharides, such as flour and cornstarch,
  are often used as thickening agents in sauces,
  desserts, and gravy.

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Linear and branched structure of polysaccharides
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• Although there are many naturally occurring
  polysaccharides, in this section we will focus on
  only four of them cellulose, starch, glycogen,
  and chitin. All play vital roles in living
  systems - cellulose and starch in plants,
  glycogen in humans and other animals, and chitin
  in arthropods.
• Polysaccharides may be divided into two
  classes homopolysaccharides, which are composed
  of one type of monosaccharide units, and
  heteropolysaccharides, which contain two or more
  different types of monosaccharide units.
• Starch, glycogen and cellulose are homoglycans
  as they are made of only glucose and are called
  glucanes or glucosanes. Homopolysaccharides which
  containe only pentoses called pentosanes, hexoses
  hexosanes. On the other hand,
  mucopolysaccharides like hyaluronic acid and
  chondroitine sulphate are heteroglycanes as they
  are made up of different monosaccharide units.
• Common formula for pentosanes (C5H8O4)n, for
  hexosanes (C6H10O5)n.

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• Homopolysaccharides
• Structure, composition and properties of
  cellulose.
• Cellulose is the most abundant polysaccharide.
  It is the structural component of the cell walls
  of plants. Approximately half of all the carbon
  atoms in the plant kingdom are contained in
  cellulose molecules. Structurally, cellulose is ?
  linear (unbranched) D-glucose polymer in which
  the glucose units are linked by ?(1-4) glycosidic
  bonds.

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• At heating with mineral acids cellulose
  hydrolyzed by the following scheme

In cellulose glucopyranose remainders have linear
structure and hydrogen bonds
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• Typically, cellulose chains contain about 5000
  glucose units, which gives macromolecules with
  molecular masses of about 900,000. Cotton is
  almost pure cellulose (95 ) and wood is about
  50 cellulose. Even though it is ? glucose
  polymer, cellulose is not ? source of nutrition
  for human beings. Humans lack the enzymes capable
  of catalyzing the hydrolysis of ? (1- 4) linkages
  in cellulose. Even grazing animals have the
  enzymes necessary for cellulose digestion.
  However, the intestinal tracts of animals such as
  horses, cows, and sheep contain bacteria that
  produce cellulose, an enzyme that can hydrolyze ?
  (1- 4) linkages and produce free glucose from
  cellulose. Thus grasses and other plant materials
  are ? source of nutrition for grazing animals.
  The intestinal tracts of termites contain the
  same microorganisms, which enable termites to use
  wood as their source of food. Microorganisms in
  the soil can also metabolize cellulose, which
  makes possible the biodegradation of dead plants.
  Despite its nondigestibility, cellulose is still
  an important component of ? balanced diet. It
  serves as dietary fiber. Dietary fiber provides
  the digestive tract with "bulk" that helps move
  food through the intestinal tract and facilitates
  the excretion of solid wastes. Cellulose readily
  absorbs water, leading to softer stools and
  frequent bowel action. Links have been found
  between the length of time stools spend in the
  colon and possible colon cancer.

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• High-fiber food may also play ? role in weight
  control. Obesity is not seen in parts of the
  world where people eat large amounts of
  fiber-rich foods. Many of the weight-loss
  products on the market are composed of
  bulk-inducing fibers such as methylcellulose.
• FIGURE. Cellulose microfibrils.
• Some fibers bind lipids such as cholesterol and
  carry out them of the body with the feces. This
  lowers blood lipid concentrations and possibly
  the risk of heart and artery disease.

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• Structure, composition and properties of
  starch.
• Starch, like cellulose, is ? polysaccharide
  containing only glucose units. It is the storage
  polysaccharide in plants. If excess of glucose
  enters ? plant cell, it is converted to starch
  and stored for later use. When the cell cannot
  get enough glucose from outside, it hydrolyzes
  starch to release glucose. Iodine is often used
  to test the presence of starch in solution.
  Starch-containing solutions turn ? dark blue when
  iodine is added. As starch is broken down through
  acid or enzymatic hydrolysis to glucose monomers,
  the blue color disappears. Two different
  polyglucose polysaccharides can be isolated from
  most starches amylose and amylopectin. Amylose,
  ? straight-chain glucose polymer, usually
  accounts for 15 20 of the starch
  amylopectin, ? highly branched glucose polymer,
  accounts for the remaining 80 85 of the
  starch.

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• In amylose's structure, the glucose units are
  connected by ?(1- 4) glycosidic linkages.
• 
  Starch (amylose)
• The number of glucose units present in an
  amylose chain depends on the source of the
  starch 200 350 monomer units are usually
  present. Amylopectin, the other polysaccharide in
  starch, is similar to amylose, but has ? high
  degree branched structure in the polymer. ? one
  branch link containe 20-25 glucose units. The
  number of glucose units present in an amylopectin
  chain consists of 1000 and more units. The branch
  points involve ?(1 6) linkages

Starch (amylopectin)
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• Because of the branching, amylopectin has ?
  larger average molecular mass than the linear
  amylose. The average molecular mass of amylose is
  40000 or more it is 1-6 mln. for amylopectin.
  Note that all of the glycosidic linkages in
  starch (both amylose and amylopectin) are of the
  ?-type. In amylose, they are all ?(1 - 4) in
  amylopectin, both ?(1 -4) and ?(1 -6) linkages
  are present. Because ? linkages can be broken
  through hydrolysis within the human digestive
  tract (with the help of the enzyme amylase),
  starch has nutritional value for humans. The
  starches present in potatoes and cereal grains
  (wheat, rice, corn, etc.) account for
  approximately two-thirds of the world' s food
  consumption.
• Fermentayion hydrolysis of starch is shown below

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• Glycogen, chitin.
• Glycogen, like cellulose and starch, is ?
  polysaccharide containing only glucose units. It
  is the glucose storage polysaccharide in humans
  and animals. Its function is thus similar to that
  of starch in plants, and it is sometimes referred
  to as animal starch. Liver cells and muscle cells
  are the storage sites for glycogen in humans.
  Glycogen has ? structure similar to that of
  amylopectin all glycosidic linkages are of the
  ?-type, and both (1-4) and (1-6) linkages are
  present. Glycogen and amylopectin differ in the
  number of glucose units between branches and the
  total number of glucose units present in ?
  molecule. Glycogen is about three times more
  highly branched than amylopectin, and it is much
  larger, with ? molar mass. ? one branch link
  containe 8-12 glucose units, rare 2- 4. When
  excess of glucose is present in the blood
  (normally from eating too much starch), the liver
  and muscle tissue convert the excess of glucose
  to glycogen, which is then stored in these
  tissues. Whenever the glucose blood level drops
  (from exercise, fasting, or normal activities),
  some stored glycogen is hydrolyzed back to
  glucose. These two opposing processes are called
  glycogenesis and glycogenolysis, the formation
  and decomposition of glycogen, respectively.

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• Glycogen is an ideal storage form for glucose.
  The large size of these macromolecules prevents
  them from diffusing out of cells. Also,
  conversion of glucose to glycogen reduces osmotic
  pressure. Cells would burst because of increased
  osmotic pressure if all of the glucose in
  glycogen were present in cells in free form. High
  concentrations of glycogen in ? cell sometimes
  cases precipitate or crystallize into glycogen
  granules. These granules are discernible in
  photographs of cells under electron microscope
  magnification. The glucose polymers amylose,
  amylopectin, and glycogen compare as follows in
  molecular size and degree of branching
• Amylose Up to 1000 glucose units no branching
• Amylopectin Up to 100,000 glucose units branch
  points every 20-25 glucose units
• Glycogen Up to 1,000,000 glucose units branch
  points every 8-12 glucose units

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• FIGURE. Structure of amylopectine (?), glycogen
  (b)

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Dextranes

• Dextranes have bacterial origin, contain
  remainders of a-D-glucopyranose. Dextranes obtain
  from saccharose at the present of bacterium
  (Leuconostoc mesenteroides). The main type of
  bond is a-1,6-glycosidic bond, in place of
  branching a-1,4- and a-1,3-glycosidic bonds.
  The average molecular mass of dextranes is few
  millions. Partly hydrolyzed dextranes (m. m.
  40000-800000) use in pharmacy as plasmasubstitute
  (Polyglucin, Reopolyglucin).

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Inuline

• Inuline reserve polysaccharide, present in
  plants. Inuline has linear structure and consists
  of remainders of ß-D-fructofuranose, joined by
  2,1-glycosidic bonds, in the end of inuline is
  a-D-glucopyranose remainder (like saccharose).
  Molecular mass of inuline is up to 6000. Use for
  obtaining of D-fructose.

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Pectin compounds

• Pectin compounds (pectins) polysaccharides
  consist of polygalacturonic acid, which contain
  remainders of a-D-galacturonic acid joined by
  1,4-glycosidic bonds. Part of carboxyl grups
  present in appearance of methyl ether. Water
  solutions of pectins form stable gels. Pectins
  have antiulcer properties.

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• Chitin is ? polysaccharide that is similar to
  cellulose in both function and structure. Its
  function is to give rigidity to the exoskeletons
  of crabs, lobsters, shrimp, insects, and other
  arthropods. It also occurs in the cell walls of
  fungi. Structurally, chitin is ? linear polymer
  (no branching) with all ?(1- 4) glycosidic
  linkages, as in cellulose. Chitin differs from
  cellulose in that the monosaccharide present is
  an N-acetylamino derivative of D-glucose.

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• Heteropolysaccharides.
• Unlike all the polysaccharides we have
  discussed up to this point, mucopolysaccharides
  are heteropolysaccharides rather than
  homopolysaccharides.
• Mucopolysaccharides are compounds that occur in
  connective tissue associated with joints in
  animals and humans. Their function is primarily
  that of lubrication, ? necessary requirement if
  movement is to occur. The name mucopolysaccharide
  comes from the highly viscous, gelatinous
  (mucus-like) consistency of these substances in
  aqueous solution.
• ? heteropolysaccharide is ? polysaccharide in
  which more than one (usually two) type of
  monosaccharide unit is present.
• One of the most common mucopolysaccharides is
  hyaluronic acid, ? heteropolysaccharide in which
  the following two glucose derivatives alternate
  in the structure.

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• It is ? highly viscous substance and has ?
  molecular weight in several hundred millions.
  Hyaluronic acid is ? principal component of the
  ground substance of connective tissue. Among
  other places it is found in skin, synovial fluid,
  vitreous hemour of the eye, and umbilical cord.
  It exercises ? cementing function in the tissues
  and capillary walls, and forms ? coating gel
  round the ovum. It accounts for about 80 of the
  viscosity of synovial fluid which contains about
  0. 02 0.05 of hyaluronate. Repeat part of
  hyaluronic acid is D-glucuronic acid and
  N-acetyl-D-glucosamine joined by ß-1,3-glycosidic
  bond, between disaccharide fragments ß-1,4.
  Molecular mass of hyaluronic acid is from 1600 to
  6400.
• (1,4)-O-?-D-Glucopyranosyluronic
  acid-(1,3)-2-acetamino-2-dezoxy-?-D-glucopyranose.
  

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• Hyaluronic acid is split up by the enzyme
  hyalurosidase into ? number of small molecule. If
  fluid containing this enzyme is injected into ?
  tissue it spreads rapidly, from the site of
  injection and thus this enzyme is sometimes
  referred as the spreading factor. It is found
  in relatively high concentration in the testis
  and seminal fluid, in the venoms of certain
  snakes and insects, and in some bacteria. The
  enzyme also has ? physiological role in
  fertilization. The sperm is rich in the enzyme
  and the former can thus advance better in the
  cervical canal and finally penetrates the ovum.

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• Chondroitin sulfate. It has similar structure
  as hyaluronic acid with the difference that the
  N-acetyl-D-glucosamine unit of the molecule is
  replaced by N-acetyl-D-galactosamine unit with
  sulphate group. Repeat part of chondroitin
  sulphate is D-glucuronic acid and
  N-acetyl-D-galactosamine which contains sulfate
  group. Inside of disaccharide fragment is
  ß-1,3-glycosidic bond between fragments ß-1,4.
  Sulfate group forms ether bond with hydroxyl
  group of N-acetyl-D-galactosamine in location 4
  (chondroitin-4-sulfate) or in location 6
  (chondroitin-6-sulfate). Chondroitin sulfates are
  found in cartilage, bone, heart valves, tendons
  and cornea.
• (1,4)-O-?-D-Glucopyranosyluronic
  acid-(1,3)-2-acetamino-2-dezoxy-6-O-sulfo-?-D-gala
  ctopyranose.

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Hydrocarbon chains of chondroitin-4-sulfate
contain up to 150 disaccharides remainders,
joined in organism by O-glycosidic bonds with
hydroxyl groups of aminoacid remainders.
50

• Dermatan sulfate. (Varying amounts of
  D-glucuronic acid may be present. Concentration
  increases during aging process.)
• (1,4)-O-?-L-idopyranosyluronic acid-(1,3)-2-acetam
  ino-2-dezoxy-4-O-sulfo-?-D-galactopyranose.

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• Heparin. It is naturally occurring
  anticoagulant found mainly in the liver, and also
  in lung, spleen, kidney and intestinal mucosa. It
  prevents blood clotting by inhibiting the
  prothrombin-thrombin conversion and thus
  eliminating the thrombin effect on fibrinogen.
  Repeat part of heparin consists of D-glucosamin
  and uronic acid, joined by a-1,4-glycosidic
  bonds. As uronic acid in heparin present
  L-iduronic acid or, very rare, D-glucuronic acid.
  Remainders of glucosamine and L-iduronic acid
  partly sulfonated. Molecular mass of heparin is
  16000-20000.

(1,4)-O-?-D-idupyranosyluronic acid-2-O-sulfo-(1,4
)-2-sulfamino-2-dezoxy-6-O-sulfo-?-D-glucopyranose
52

• 5. Glycoconjugates.
• The compounds that result from the covalent
  linkages of carbohydrate molecules to both
  proteins and lipids are collectively known as the
  glycoconjugates. These substances have profound
  effects on the function of individual cells, as
  well as the cell-cell interactions of
  multicellular organisms. There are two classes of
  carbohydrate-protein conjugate proteoglycans and
  glycoproteins. Although both molecular types
  contain ???bohydrate and protein, their
  structures and functions appear, in general, to
  be substantially different. The glycolipids,
  which are oligosaccharide-containing lipid
  molecules, are found predominantly on the outer
  surface of plasma membranes.

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• Proteoglycans are distinguished from the common
  glycoproteins by their extremely high
  carbohydrate content, which may constitute as
  much as 95 of the dry weight of such molecules.
  These molecules are found predominantly in the
  extracellular matrix (intercellular material) of
  tissues. All proteoglycans contain GAG chains.
  The GAG chains are linked to protein molecules
  (known as core proteins) by N- and O-glycosidic
  linkages. The diversity of proteoglycans is ?
  result of both the number of different core
  proteins and the large variety of different
  classes and length of the carbohydrate chains.

54
Fig. Proteoglycan structure
55

• Because proteoglycans contain large numbers of
  GAGs, which are polyanions, large volumes of
  water and cations are trapped within their
  structure. As ? result, proteoglycan molecules
  occupy space that is thousands of times bigger
  that of ? densely packed molecule of the same
  mass. Proteoglycans contribute support and
  elasticity to tissues in which they occur.
  Consider, for example, the strength, flexibility,
  and resilience of cartilage. The structural
  diversity of proteoglycans allows them to serve ?
  variety of structural and functional roles in
  living organisms. Proteoglycans are particularly
  abundant in the extracellular matrix of
  connective tissue. Together with matrix proteins
  such as collagen, fibrinogen and laminin, they
  form an organized meshwork that provides strength
  and support to multicellular tissues.
  Proteoglycans are also present at the surface of
  cells, where they are directly bound with the
  plasma membrane. Although the function of these
  latter molecules is not yet clear, the suggestion
  has been made that they play an important role in
  membrane structure and cell-cell interactions.

56

• ? number of genetic diseases associated with
  proteoglycan metabolism, known as
  mucopolysaccharidoses, have been identified.
  Because proteoglycans are constantly being
  synthesized and degraded, their excessive
  accumulation (due to missing or defective
  lyzosomal enzymes) has very serious consequences.
  For example, in Hurler's syndrome, an autosomal
  recessive disorder (? disease type in which one
  copy of the defective gene is inherited from each
  parent), deficiency of ? specific enzyme results
  in accumulation of dermatan sulfate. Symptoms
  include mental retardation, skeletal deformity,
  and early childhood death. Glycoproteins are
  commonly defined as proteins that are covalently
  linked to carbohydrate through O- or N-linkages.
  The carbohydrate contain of glycoprotein varies
  from 1 to over 85 of total weight. The types of
  carbohydrate that are founded include
  monosaccharides and disaccharides such as those
  attached to the structural protein collagen and
  branched oligosaccharides on plasma
  glycoproteins. Although the glycoproteins are
  sometimes considered to include the
  proteoglycans, there appear to be sufficient
  structural reasons to examine them separately.

57

• These substances include glycoproteins of
  uronic acids, sulfate groups and disaccharide
  repeating units that are typical for
  proteoglycans. The carbohydrate groups of
  glycoproteins are linked to the polypeptide by
  either (1) an N-glycosidic linkage between
  N-acetylglucosamine (GlcNAc) and the aminoacid
  asparagine (Asn) or (2) an O-glycosidic linkage
  between N-acetylgalactosamine (GalNAc) and the
  hydroxyl group of the ?minoacids serine (Ser) or
  threonine (Thr). The former glycoprotein class is
  sometimes referred to as asparagine-linked the
  latter is often called mucin-type.

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• Asparagine-linked carbohydrates. As was mentioned
  previously, three structural forms of
  asparagine-linked oligosaccharide occur in
  glycoproteins high- mannose, complex, and
  hybrid. High-mannose type is composed of GlcNAc
  and mannose. Complex-type may contain fructose,
  galactose, and sialic acid in addition to GlcNAc
  and mannose. Hybrid-type oligosaccharides contain
  features of both complex and high-mannose-type
  species. Despite these differences, the core
  structure of all N-linked oligosaccharides is the
  same. This core, which is constructed on ?
  membrane-bound lipid molecule, is covalently
  linked to asparagine during protein synthesis.
  Several additional reactions, which occur within
  the lumen of the endoplasmic reticulum and the
  Golgi complex, result in the final N-linked
  oligosaccharide structures.

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• Mucin-type carbohydrate While all N-linked
  oligosaccharides are bound to protein via
  GlcNAc-Asn, the linking groups of O-glycosidic
  oligosaccharides are of several types. The most
  common of these is GalNAc-Ser (or GalNAc-Thr).
  Considerable mucin-type carbohydrate unit is
  disaccharide such as Gal-1,3-GalNAc, found in the
  antifreeze glycoprotein of antarctic fish
  (Figure), to the complex oligosaccharides of
  blood groups such as those of the ABO system.
• Fig. Antifreeze glycoprotein structure.

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6. Lipids

• Lipids differ from the other classes of
  naturally occurring biomolecules (carbohydrates,
  proteins, and nucleic acids), they are more
  soluble in non- or weakly polar solvents (diethyl
  ether, hexane, dichloromethane) than in water.
  They include a variety of structural types, a
  collection of which is introduced in this
  chapter. In spite of the number of different
  structural types, lipids share a common
  biosynthetic origin in that they are ultimately
  derived from glucose. During one stage of
  carbohydrate metabolism, called glycolysis,
  glucose is converted to lactic acid. Pyruvic acid
  is an intermediate product.

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Classification of lipids
62

• Classification Lipids can be divided into two
  major classes on the basis of whether they
  undergo hydrolysis reactions in alkaline (basic)
  solution. Saponifiable lipids can be hydrolyzed
  under alkaline conditions to yield salts of fatty
  acids. Nonsaponifiable lipids do not undergo
  hydrolysis reactions in alkaline solution.
• The basis of the nature of the products obtained
  on hydrolysis lipids are mainly divided into
  three type simple, compound and derived lipids.
• 1. Simple lipids. These are esters of fatty acids
  and alcohols and thus on hydrolysis give fatty
  acids and alcohols. They may be of two types.
• ?) Fats and oils. These are esters of fatty acids
  and glycerol (? trihydric alcohol). These are
  also known as glycerides.
• b) Waxes. These are esters of long-chain fatty
  acids and long-chain monohydric alcohols or
  sterols.
• 2 Compound lipids. Compound lipids are esters of
  fatty acids and alcohols in combination with
  other compound and thus on hydrolysis give fatty
  acids, alcohol and other compounds. On the basis
  of the nature of the other group, compound lipids
  may again be of following types.
• ?) Phospholipids. These are fat like compounds
  containing phosphoric acid and ? nitrogen base.
• b) Glycolipids. These are compounds containing ?
  fatty acid, ? carbohydrate, ? complex alcohol,
  and nitrogen, but n? phosphorus.
• 3. Derived lipids. These compounds although do
  not contain an ester linkage but are obtained by
  the hydrolysis of simple and compound lipids.
  They may be fatty acids, alcohols and sterols.

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• Lipids are organic compounds, found in living
  organisms, that are soluble in nonpolar organic
  solvents. Because compounds are classified as
  lipids on the basis of a physical property their
  solubility in an organic solventrather than as a
  result of their structures, lipids have a variety
  of structures and functions, as the following
  examples illustrate

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65
Functions of lipids

• The most important role of lipids is as ?
  fuel. Much of the carbohydrates of the diet are
  converted to fat which is stored in various
  tissues and utilised at the time of requirement.
  Thus fat may be the major source of energy for
  many tissues. Actually, in some respects lipids
  (fats) are even superior to carbohydrates as
  source of energy.
• Fatty acids with their flexible backbones
  can be stored in ? much more compact form than
  the highly spatially oriented and rigid glycogen
  structure. Thus fat storage provides economy in
  both weight and space. In addition to the above
  three reasons there are two other reasons for fat
  storage as an excellent form of energy.
• As it is insoluble in water, it has been
  carried to the fat depots by the specialised
  transport proteins in the plasma.
• It remains as ? stable and fixed reserve of
  energy until mobilized by enzymes which hydrolyse
  it to glycerol and fatty acids. The enzymes are
  under the control of various hormones and are
  activated under conditions where the body is
  involved in increased energy expenditure.

66

• Fat may also provide padding to protect the
  internal organs. Brain and nervous tissue are
  rich in certain lipids, ? fact which indicates
  the importance of these compounds to life.
• Some compounds derived from lipids are
  important building blocks of biologically active
  materials ?.g. acetic acid can be used by the
  body to synthesize cholesterol and related
  compounds (hormones).
• Lipoproteins are constituents of cell
  walls. The lipids present in lipoproteins
  constituting the cell walls are of the types of
  phospholipids. Since lipids are water insoluble
  they act as ideal barrier for preventing water
  soluble materials from passing freely between the
  intra- and extra-cellular fluids.
• One more important function of dietary
  lipids is that of supplying the so-called
  essential fatty acids although there are several
  functions (essential fatty acids (EFA), none of
  them are well defined.

67

• Fats and oils are naturally occurring mixtures
  of triacylglycerols, also called
  triglycerides.They differ in that fats are solids
  at room temperature and oils are liquids. We
  generally ignore this distinction and refer to
  both groups as fats. Triacylglycerols are built
  on a glycerol framework.
• Simple triacylglycerines include similar fatty
  acids , mixed different. All
  three acyl groups in a triacylglycerol may be the
  same, all three may be different, or one may be
  different from the other two.

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69
Nomenclature, methods of getting of fats
For simple glycerides the name is made up of the
name of the alcohol (glycerol) or its radical
(glyceryl) and the name of the acid or the name
of the acid concerned is changed to suffix in.
For mixed glycerides, the position and names of
the acid groups are specified by Greek letters a,
ß, a or by the numerals 1, 2 and 3.

• Methods of getting
• O-acylation of alcohols
• Allocation from plants melting out, pressing or
  extraction by organic solvents.

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• Fatty acids are carboxylic acids with long
  hydrocarbon chains. Because they are synthesized
  from acetate, a compound with two carbon atoms,
  most naturally occurring fatty acids contain an
  even number of carbon atoms and are unbranched.
  Fatty acids can be saturated with hydrogen (and
  therefore have no carboncarbon double bonds) or
  unsaturated (have carboncarbon double bonds).
  Fatty acids with more than one double bond are
  called polyunsaturated fatty acids. Double bonds
  in naturally occurring unsaturated fatty acids
  are never conjugated they are always separated
  by one methylene group. The physical properties
  of a fatty acid depend on the length of the
  hydrocarbon chain and the degree of unsaturation.
  As expected, the melting points of saturated
  fatty acids increase with increasing molecular
  weight because of increased Van-der-Waals
  interactions between the molecules

71
The most widespread fatty acids in natural oils
and fats
72

• Double bonds are rigid structures, unsaturared
  acid molecules that contain them can occur in two
  isomeric forms cis and trans. In cis-isomers,
  for example, similar or identical groups are on
  the same side of double bond (a). When such
  groups are on opposite sides of a double bond,
  the molecule is said to be a trans-isomer (b)
• The double bonds in unsaturated fatty acids
  generally have the cis configuration. This
  configuration produces a bend in the molecules,
  which prevents them from packing together as
  tightly as fully saturated fatty acids. As a
  result, unsaturated fatty acids have fewer
  intermolecular interactions and, therefore, lower
  melting points than saturated fatty acids with
  comparable molecular weights . The melting points
  of the unsaturated fatty acids decrease as the
  number of double bonds increases. For example, an
  18-carbon fatty acid melts at 69 C if it is
  saturated, at 13 C if it has one double bond, at
  if it has two -5 C o double bonds, and at -11 C
  if it has three double bonds.

73

• Triacylglycerols, also called triglycerides,
  are compounds in which the three OH-groups of
  glycerol are esterified with fatty acids. If the
  three fatty acid components of a triacylglycerol
  are the same, the compound is called a simple
  triacylglycerol. Mixed triacylglycerols, on the
  other hand, contain two or three different fatty
  acid components and are more common than simple
  triacylglycerols. Not all triacylglycerol
  molecules from a single source are necessarily
  identical substances such as lard and olive oil,
  for example, are mixtures of several different
  triacylglycerols.

74
Triacylglycerols that are solids or semisolids
at room temperature are called fats. Fats are
usually obtained from animals and are composed
largely of triacylglycerols with either saturated
fatty acids or fatty acids with only one double
bond. The saturated fatty acid tails pack closely
together, giving the triacylglycerols relatively
high melting points, causing them to be solids at
room temperature. Liquid triacylglycerols are
called oils. Oils typically come from plant
products such as corn, soybeans, olives, and
peanuts. They are composed primarily of
triacylglycerols with unsaturated fatty acids
that cannot pack tightly together. Consequently,
they have relatively low melting points, causing
them to be liquids at room temperature.
75
Hydrolysis of ? triacylglycerol

• Hydrolysis of ? triacylglycerol is the reverse
  of the esterification reaction by which it wet
  formed. Complete hydrolysis of ? triacylglycerol
  molecule always gives one glycerol molecule and
  three fatty acid molecules as products.

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7. Chemical properties of fats

• 1). Hydrolysis of fats with alkali (e.g., sodium
  hydroxide) yields salts of thefatty acids, and
  those of the alkali metals, such as sodium or
  potassium, are useig as soaps. Another name of
  this reaction saponification

The solubility of lipids in nonpolar organic
solvents results from their significant
hydrocarbon component. The hydrocarbon portion of
the compound is responsible for its oiliness or
fattiness. The word lipid comes from the Greek
lipos, which means fat.
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Characterization of fats. The composition,
quality and purity of ? given oil or fat is
determined by means of ? number of physical and
chemical tests. The usual physical tests include
determination of m, ?, specific gravity,
viscosity, etc. while the chemical tests include
determination of certain values discussed below.

• 1. Acid number. It is the number of milligrams of
  potassium hydroxide required to neutralise the
  free fatty acids in 1g. of the oil or fat. Thus
  it indicates the amount of free fatty acids
  present in oil or fat. ? high acid value
  indicates ? stale oil or fat stored under
  improper conditions.
• 2. Saponification number. It is number of
  milligrams of potassium hydroxide required to
  completely hydrolysis of l g. of the oil or fat.
  Thus it is ? measure of fatty acids present as
  esters in ? given oil or fat. The saponification
  value gives an idea about the molecular weight of
  fat or oil. The saponification number and
  molecular weight of an oil are inversely
  proportional to each other thus high
  saponification number indicates that the fat is
  made up of low molecular weight fatty acids and
  vice versa. It is also helpful in detecting
  adulteration of ? given fat by one of the lower
  or higher saponfication value.
• 3. Iodine number. It is the number of grams of
  iodine that combine with 100 g. of oil or fat. It
  is ? measure of the degree of unsaturation of ?
  fat or oil ? high iodine number indicates ? high
  degree of unsaturation of the fatty acids of the
  fat.
• Difference between saponification and acid
  numbers named ether number which characterizes
  contain of the remainders of fatty acids.

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• 2). Oxidation of fates. Oxidation cases rancidity
  of fates. During oxidation form aldehydes with
  short carbon chain.

Oxidation at the soft conditions (water solution
of KMnO4) cases formation of glycols. At the
rigid conditions carbon skeleton destroys with
formation of remainders of carbonic acids with
shorter carbon chains.
79
Fats, which predominantly contain saturated fatty
acids, by oxidation form ketones.
80

• 3). Hydrogenation. Some or all of the double
  bonds of polyunsaturated oils can be reduced by
  catalytic hydrogenation. Margarine and shortening
  are prepared by hydrogenating vegetable oils such
  as soybean oil and sunflower oil until they have
  the desired consistency. This process is called
  hardening of oils. The hydrogenation reaction
  must be carefully controlled, however, because
  reducing all the carboncarbon double bonds would
  produce a hard fat with the consistency of beef
  tallow. Quantity of H2 in grams, which are
  necessary for hydration of 10kg of fats
  (hydration number) characterizes unsaturating of
  fat.

81

• 4). Addition of halogens.

Iodine number for plants fats 100-200, for
animal fats 25-86, for fish fats 100-193.
82

• As might be expected from the properties of the
  fatty acids, fats have a predominance of
  saturated fatty acids, and oils are composed
  largely of unsaturated acids. Thus, the melting
  points of triglycerides reflect their
  composition, as shown by the following examples.
  Natural mixed triglycerides have somewhat lower
  melting points, the melting point of lard being
  near 30 º C, whereas olive oil melts near -6 º C.
  Since fats are valued over oils by some Northern
  European and North American populations,
  vegetable oils are extensively converted to solid
  triglycerides (e.g. Crisco) by partial
  hydrogenation of their unsaturated components.
  Some of the remaining double bonds are isomerized
  (to trans) in this operation. These saturated and
  trans-fatty acid glycerides in the diet have been
  linked to long-term health issues such as
  atherosclerosis.

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8. Phospholipids. Waxes.

• Triacylglycerols arise, not by acylation of
  glycerol itself, but by a sequence of steps in
  which the first stage is acyl transfer to
  L-glycerol 3-phosphate (from reduction of
  dihydroxyacetone 3-phosphate, formed as described
  in Section 25.21). The product of this stage is
  called a phosphatidic acid.

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• Hydrolysis of the phosphate ester function of
  the phosphatidic acid gives a diacylglycerol,
  which then reacts with a third acyl coenzyme A
  molecule to produce a triacylglycerol.
  Phosphatidic acids not only are intermediates in
  the biosynthesis of triacylglycerols but also are
  biosynthetic precursors of other members of a
  group of compounds called phosphoglycerides or
  glycerol phosphatides. Phosphorus-containing
  derivatives of lipids are known as phospholipids,
  and phosphoglycerides are one type of
  phospholipid. One important phospholipid is
  phosphatidylcholine, also called lecithin.
  Phosphatidylcholine is a mixture of diesters of
  phosphoric acid.

85

• An animated display of micelle formation is
  presented below. Notice the brownish material in
  the center of the three-dimensional drawing on
  the left. This illustrates a second important
  factor contributing to the use of these
  amphiphiles as cleaning agents. Micelles are able
  to encapsulate nonpolar substances such as grease
  within their hydrophobic center, and thus
  solubilize it so it is removed with the wash
  water. Since the micelles of anionic amphiphiles
  have a negatively charged surface, they repel one
  another and the nonpolar dirt is effectively
  emulsified. To summarize, the presence of a soap
  or a detergent in water facilitates the wetting
  of all parts of the object to be cleaned, and
  removes water-insoluble dirt by incorporation in
  micelles. If the animation has stopped, it may be
  restarted by clicking on it.

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Classification of phospholipids
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• The oldest amphiphilic cleaning agent known to
  humans is soap. Soap is manufactured by the
  base-catalyzed hydrolysis (saponification) of
  animal fat (see below). Before sodium hydroxide
  was commercially available, a boiling solution of
  potassium carbonate leached from wood ashes was
  used. Soft potassium soaps were then converted to
  the harder sodium soaps by washing with salt
  solution. The importance of soap to human
  civilization is documented by history, but some
  problems associated with its use have been
  recognized. One of these is caused by the weak
  acidity (pKa ca. 4.9) of the fatty acids.
  Solutions of alkali metal soaps are slightly
  alkaline (pH 8 to 9) due to hydrolysis. If the pH
  of a soap solution is lowered by acidic
  contaminants, insoluble fatty acids precipitate
  and form a scum. A second problem is caused by
  the presence of calcium and magnesium salts in
  the water supply (hard water). These divalent
  cations cause aggregation of the micelles, which
  then deposit as a dirty scum.

89
Washing action of soaps
90
Waxes

• Waxes are water-repelling solids that are part
  of the protective coatings of a number of living
  things, including the leaves of plants, the fur
  of animals, and the feathers of birds. They are
  usually mixtures of esters in which both the
  alkyl and acyl group are unbranched and contain a
  dozen or more carbon atoms. Beeswax, for example,
  contains the ester triacontyl hexadecanoate as
  one component of a complex mixture of
  hydrocarbons, alcohols, and esters.

91

• Wax is ? mixture of esters of high molecular
  weight alcohols and high molecular weight fatty
  acids.
• Waxes are sa??infied with great difficulty than
  fats and are not attacked by lipase. Although
  waxes may be saponified by prolonged boiling with
  alcoholic KOH, they are more easily saponified by
  treating ? solution of the wax in petroleum ether
  with absolute alcohol and metallic sodium, with
  sodium ethoxide. The saponification products ?f
  waxes are water-soluble soaps (sodium Its of
  higher fatty acids) while the water insoluble
  long-chain alcohols appear in the "unsaponifiable
  matter" fraction. Waxes contain about 31 -55 of
  the unsaponifiable matter, while fats and oils
  contain only 1 - 2 unsaponifiable matter.
• Waxes dividing on animals (spermaceti, bees wax,
  lanoline and others) and plants (carnauba wax).

92

• Bees wax. It contains esters derived from
  alcohols having 24 - 30 carbon atoms, include
  palmitate of miri??l alcohol (?30H61??) and
  n-hexacosanol (?26?53??).
• ??3(C?2)14COOC30H61 ??3
  (C?2)14COOC26H53
• miricyl patmitate n-
  hexacosanyl patmitate
• Spermaceti. It is obtained from the head of the
  sperm whale. It is rich in ester of cetyl alcohol
  (?16?33??) and palmitinic acid ??3 (C ?2 )
  14COOC16H33 - cetyl palmitate
• Spermaceti is used in making of candles.
• Sperm Oil. It is ? liquid wax and occurs with
  spermaceti in the sperm whale. It is ? valuable
  lubricant used for delicate instruments, such as
  watches. It does not become gummy, as many oils
  do.
• Carnauba wax. It is found in the leaves of the
  carnauba palm of Brazil. It is used as an
  ingredient in the manufacture of various wax
  polishes. Because waxes are very inert
  chemically, they make an excellent protective
  coating.
• Lanolin or wool wax. It is obtained from wool and
  is used in making ointments and salves.

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9. Nonsaponifiable lipids

• 1). Prostaglandins physiologically active
  substances with biogenic origin, stimulate smooth
  muscles and lowers blood pressure. All
  prostaglandins contain carboxyl group and 20
  carbon atoms in molecule, they are derivatives of
  eyicosanic acid.

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• Research in physiology carried out in the 1930s
  established that the lipid fraction of semen
  contains small amounts of substances that exert
  powerful effects on smooth muscle. Sheep prostate
  glands proved to be a convenient source of this
  material and yielded a mixture of structurally
  related substances referred to collectively as
  prostaglandins. We now know that prostaglandins
  are present in almost all animal tissues, where
  they carry out a variety of regulatory functions.
  Prostaglandins are extremely potent substances
  and exert their physiological effects at very
  small concentrations. Because of this, their
  isolation was difficult, and it was not until
  1960 that the first members of this class,
  designated PGE1 and PGF1, were obtained as pure
  compounds.

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All the prostaglandins are 20-carbon carboxylic
acids and contain a cyclopentane ring. All have
hydroxyl groups at C-11 and C-15 (for the
numbering of the positions in prostaglandins).
Prostaglandins belonging to the F series have an
additional hydroxyl group at C-9, and a carbonyl
function is present at this position in the
various PGEs. The subscript numerals in their
abbreviated names indicate the number of double
bonds. Prostaglandins are believed to arise from
unsaturated C20-carboxylic acids such as
arachidonic acid. Mammals cannot biosynthesize
arachidonic acid directly.
96

• They obtain linoleic acid from vegetable oils
  in their diet and extend the carbon chain of
  linoleic acid from 18 to 20 carbons while
  introducing two more double bonds. Linoleic acid
  is said to be an essential fatty acid, forming
  part of the dietary requirement of mammals.
  Animals fed on diets that are deficient in
  linoleic acid grow poorly and suffer a number of
  other disorders, some of which are reversed on
  feeding them vegetable oils rich in linoleic acid
  and other polyunsaturated fatty acids. One
  function of these substances is to provide the
  raw materials for prostaglandin biosynthesis.

97

• Physiological responses to prostaglandins
  encompass a variety of effects. Some
  prostaglandins relax bronchial muscle, others
  contract it. Some stimulate uterine contractions
  and have been used to induce therapeutic
  abortions. PGE1 dilates blood vessels and lowers
  blood pressure it inhibits the aggregation of
  platelets and offers promise as a drug to reduce
  the formation of blood clots. The long-standing
  question of the mode of action of aspirin has
  been addressed in terms of its effects on
  prostaglandin biosynthesis. Prostaglandin
  biosynthesis is the bodys response to tissue
  damage and is manifested by pain and inflammation
  at the affected site. Aspirin has been shown to
  inhibit the activity of an enzyme required for
  prostaglandin formation. Aspirin reduces pain and
  inflammationand probably fever as wellby
  reducing prostaglandin levels in the body.

98

• Much of the fundamental work on prostaglandins
  and related compounds was carried out by Sune
  Bergström and Bengt Samuelsson of the Karolinska
  Institute (Sweden) and by Sir John Vane of the
  Wellcome Foundation (Great Britain). These three
  shared the Nobel Prize for physiology or medicine
  in 1982. Bergström began his research on
  prostaglandins because he was interested in the
  oxidation of fatty acids. That research led to
  the identification of a whole new class of
  biochemical mediators. Prostaglandin research has
  now revealed that other derivatives of oxidized
  polyunsaturated fatty acids, structurally
  distinct from the prostaglandins, are also
  physiologically important. These fatty acid
  derivatives include, for example, a group of
  substances known as the leukotrienes, which have
  been implicated as mediators in immunological
  processes.

99

• Prostaglandins have cyclopentane ring.
  According to allocation of double bonds in