CarbohydratesCarbohydrates

Chapter 8Chapter 8

CarbohydratesCarbohydrates Of the macromolecules that we will Of the macromolecules that we will

cover in this class, those involving cover in this class, those involving carbohydrates are the most abundant carbohydrates are the most abundant in nature.in nature.

Via photosynthesis, over 100 billion Via photosynthesis, over 100 billion metric tons of COmetric tons of CO22 and H and H22O are O are converted into cellulose and other converted into cellulose and other plant products. plant products.

The term carbohydrate is a generic The term carbohydrate is a generic one that refers primarily to carbon-one that refers primarily to carbon-containing compounds that contain containing compounds that contain hydroxyl, keto, or aldehydic hydroxyl, keto, or aldehydic functionalities.functionalities.

Carbohydrates can range in sizes, Carbohydrates can range in sizes, from simple monosaccharides from simple monosaccharides (sugars) to oligosaccharides, to (sugars) to oligosaccharides, to polysaccharides.polysaccharides.

CarbohydratesCarbohydrates Carbohydrates constitute more than 1/2 of organic moleculesCarbohydrates constitute more than 1/2 of organic molecules Main role of carbos in natureMain role of carbos in nature

Storage of energy Storage of energy Structural supportStructural support Lipid and protein modification:Lipid and protein modification:

membranes asymmetry, recognition by membranes asymmetry, recognition by IgG/fertilization/virus recognition/cell cell IgG/fertilization/virus recognition/cell cell communicationcommunication

Definition: Carbohydrates, Sugars and Saccharides- are all polyhydroxy Definition: Carbohydrates, Sugars and Saccharides- are all polyhydroxy (at least 2 OH) C(at least 2 OH) Cnn(H(H220)0) n n = hydrate of carbon = hydrate of carbon

Notice that there are two distinct types of monosaccharides, ketoses Notice that there are two distinct types of monosaccharides, ketoses and aldoses. and aldoses.

The number of carbons is important in general nomenclature (triose The number of carbons is important in general nomenclature (triose = 3, pentose = 5, hexose =6,= 3, pentose = 5, hexose =6,

Basic factsBasic facts Monosaccharides Monosaccharides - Simple sugars- Simple sugars

Single polyhydroxyl Single polyhydroxyl Can’t be hydrolyzed to simpler formCan’t be hydrolyzed to simpler form

TriosesTrioses - Smallest monosaccharides have three carbon - Smallest monosaccharides have three carbon atomsatoms

TetrosesTetroses (4C) (4C) PentosePentose (5C) (5C) HexosesHexoses (6C) (6C) HeptosesHeptoses (7C) (7C) etc…etc…

DisaccharideDisaccharide - two sugars linked together. Can be the - two sugars linked together. Can be the same molecule or two different sugars. Attached same molecule or two different sugars. Attached together via a glycosidic linkagetogether via a glycosidic linkage

OligosaccharideOligosaccharide - 2 to 6 monosaccharides - 2 to 6 monosaccharides

PolysaccharidesPolysaccharides - straight or branched long chain - straight or branched long chain monosaccharides. Bonded together by glycosidic monosaccharides. Bonded together by glycosidic linkageslinkages

The functional groupsThe functional groups Aldehyde:Aldehyde: Consists of a carbon atom Consists of a carbon atom

bonded to a hydrogen atom and bonded to a hydrogen atom and double-bonded to an oxygen atom.double-bonded to an oxygen atom.– Polar. Oxygen, more electronegative than carbon, Polar. Oxygen, more electronegative than carbon,

pulls the electrons in the carbon-oxygen bond pulls the electrons in the carbon-oxygen bond towards itself, creating an electron deficiency at towards itself, creating an electron deficiency at the carbon atom.the carbon atom.

Ketone:Ketone: Characterized by a carbonyl Characterized by a carbonyl group (O=C) linked to two other carbon group (O=C) linked to two other carbon atoms or a chemical compound that atoms or a chemical compound that contains a carbonyl groupcontains a carbonyl group

– A carbonyl carbon bonded to two carbon atoms A carbonyl carbon bonded to two carbon atoms distinguishes ketones from carboxylic acids, distinguishes ketones from carboxylic acids, aldehydes, esters, amides, and other oxygen-aldehydes, esters, amides, and other oxygen-containing compounds containing compounds

Classification of Classification of monosaccharidesmonosaccharides

Monosaccharides are classified according to Monosaccharides are classified according to three different characteristics: three different characteristics: – the placement of its carbonyl group,the placement of its carbonyl group,– the number of carbon atoms it the number of carbon atoms it

containscontains– its chiral handedness. its chiral handedness.

If the carbonyl group is an aldehyde, the If the carbonyl group is an aldehyde, the monosaccharide is an aldosemonosaccharide is an aldose

if the carbonyl group is a ketone, the if the carbonyl group is a ketone, the monosaccharide is a ketose. monosaccharide is a ketose.

Monosaccharides with three carbon atoms Monosaccharides with three carbon atoms are called trioses, those with four are are called trioses, those with four are called tetroses, five are called pentoses, called tetroses, five are called pentoses, six are hexoses, and so on. six are hexoses, and so on. 

These two systems of classification are These two systems of classification are often combined. often combined. – For example, glucose is For example, glucose is

an aldohexose (a six-carbon an aldohexose (a six-carbon aldehyde)aldehyde)

carbonyl groupcarbonyl group

A functional group composed A functional group composed of a carbon atom double-of a carbon atom double-bonded to an oxygen atom: bonded to an oxygen atom: C=O.C=O.

The term carbonyl can also The term carbonyl can also refer to carbon monoxide as refer to carbon monoxide as a ligand in a ligand in an inorganic or organometallian inorganic or organometallic  complex.c  complex.

Classification of Classification of monosaccharidesmonosaccharides

D-glucose D-glucose 

is an aldohexose with the formula is an aldohexose with the formula (C·H2O)6. (C·H2O)6.

The red atoms highlight the The red atoms highlight the aldehyde groupaldehyde group

the blue atoms highlight the the blue atoms highlight the asymmetric center furthest from asymmetric center furthest from the aldehyde; because this -OH is the aldehyde; because this -OH is on the right of the Fischer on the right of the Fischer projection, this is a D sugar.projection, this is a D sugar.

Classification of Classification of monosaccharidesmonosaccharides

The α and β anomers of glucose. The α and β anomers of glucose.

Note the position of the hydroxyl Note the position of the hydroxyl group (red or green) on the group (red or green) on the anomeric carbon relative to the anomeric carbon relative to the CH2OH group bound to carbon 5: CH2OH group bound to carbon 5:

Either on the opposite sides (α)Either on the opposite sides (α)

Or the same side (β).Or the same side (β).

Steriochemistry- optically active molecules- optically active moleculesD or L as designated by furthest asymmetric D or L as designated by furthest asymmetric

carbon from ketone or aldehydecarbon from ketone or aldehydeoptical activity is independent of D or L optical activity is independent of D or L

designation D(-) fructosedesignation D(-) fructose

Increase in number of carbons increase possible Increase in number of carbons increase possible stereoisomers: Van’t Hoff’s Rule: A compound stereoisomers: Van’t Hoff’s Rule: A compound with n asymmetric C atoms has a maximum of with n asymmetric C atoms has a maximum of 2n possible stereoisomers2n possible stereoisomers

Enantiomers: Stereoisomers that are non superimposable Enantiomers: Stereoisomers that are non superimposable mirror imagesmirror images

ex. L and D forms of sugars D-glyceraldehyde and L-ex. L and D forms of sugars D-glyceraldehyde and L-glyceraldehydeglyceraldehyde

Chirality in MonosaccharidesChirality in Monosaccharides Most simple Most simple

monosaccharides have at monosaccharides have at least one least one chiralchiral center. As center. As in the case of amino acids, in the case of amino acids, sugars are given D or L sugars are given D or L designations based on their designations based on their similarity with D or L similarity with D or L glyceraldehyde (shown on glyceraldehyde (shown on left).left).

Since some sugars contain Since some sugars contain many chiral centers, many chiral centers, it is it is necessary to designate one necessary to designate one chiral center that will act as chiral center that will act as the referencethe reference. This chiral . This chiral center is designated as the center is designated as the one that is one that is most distantmost distant from the carbon that bears from the carbon that bears the carbonyl functionality.the carbonyl functionality.

Chirality in MonosaccharidesChirality in Monosaccharides Sugars are frequently written Sugars are frequently written

as Fischer projections. as Fischer projections. Remember that atoms that lie Remember that atoms that lie on horizontal bonds are on horizontal bonds are projecting towards you, while projecting towards you, while those on vertical bonds are those on vertical bonds are projecting away from you.projecting away from you.

Compare the top and bottom Compare the top and bottom structures for glyceraldehyde.structures for glyceraldehyde.

The numbering of carbons in The numbering of carbons in sugars begins at the end of the sugars begins at the end of the chain that is closer to the chain that is closer to the carbonyl functionality.carbonyl functionality.

If the carbonyl group is an If the carbonyl group is an aldehyde the sugar is an aldehyde the sugar is an aldosealdose..

Arrows indicate Sterochemical Arrows indicate Sterochemical relationshipsrelationships

Configuration around C2 Configuration around C2 (red)(red) distinguishes the members of distinguishes the members of each pair of monosaccharideseach pair of monosaccharides

Most common aldoses:Most common aldoses:– D-Ribose (Rib)D-Ribose (Rib)– D-Glucose (Glc)D-Glucose (Glc)– D-Mannose (Man)D-Mannose (Man)– D-Galactose (Gal)D-Galactose (Gal)– D-Xylose (Xyl)D-Xylose (Xyl)– D-Arabinose (Ara)D-Arabinose (Ara)

ALL BASED ON THE STRUCTURE ALL BASED ON THE STRUCTURE OF OF GLYCERALDEHYDEGLYCERALDEHYDE

If the carbonyl group is an If the carbonyl group is an ketone the sugar is an ketone the sugar is an ketoseketose

Arrows indicate Sterochemical Arrows indicate Sterochemical relationshipsrelationships

Configuration around C3 Configuration around C3 (red)(red) distinguishes the members of distinguishes the members of each pair of monosaccharideseach pair of monosaccharides

Most common Ketoses:Most common Ketoses:– D-Fructose (Fru)D-Fructose (Fru)– D-Ribulose (Rib)D-Ribulose (Rib)

ALL BASED ON THE ALL BASED ON THE STRUCTURE OF STRUCTURE OF DihydroxyacetoneDihydroxyacetone

EpimersEpimers EpimersEpimers are two sugars that differ only in are two sugars that differ only in

the configuration around one carbon atom of the configuration around one carbon atom of their structures.their structures.

D-Mannose differs from D-glucose only in its D-Mannose differs from D-glucose only in its configuration around carbon 2.configuration around carbon 2.

D-Galactose differs from D-glucose only in D-Galactose differs from D-glucose only in its configuration around carbon 4.its configuration around carbon 4.

D-Galactose and D-Mannose are not epimersD-Galactose and D-Mannose are not epimers..

Conformational StructuresEmil Fisher - Nobel Prize 1891

Organic chemist who found the structure of D glucose

Fisher projections - place most oxidized carbon on top

Haworth Structures: carbons counted from anomeric C to clockwise from the oxygen in the ring (pyranose) or the #2 C for furanose– OH in down position -

form– OH in up position - ß form

Carbohydrates of four carbons and more are found in cyclic forms. How?

Aldehydes and ketones react reversibly with -OH on sugars

5 or 6 carbon rings most stable 4 carbon membered ring furan - ribose 5 carbon membered ring pyran - glucose

- straight chains form hemiacetals and hemi ketals

Cyclization of MonosaccharidesCyclization of Monosaccharides

Carbohydrates of four carbons and more are found in cyclic forms How?

C=O at reference carbon is reduced to OH

Formation of ring structure leads to an additional chiral carbon (anomeric carbon) This is the number one carbon in the pyranose structures, #2 for the furanoses

Cyclization of MonosaccharidesCyclization of Monosaccharides In hexoses, an attack of In hexoses, an attack of

the hydroxyl group at C-5 the hydroxyl group at C-5 onto the aldehyde onto the aldehyde functionality generates a functionality generates a cyclic structure cyclic structure containing six containing six substituents.substituents.

One of the substituents is One of the substituents is an oxygen, which acted an oxygen, which acted as the nucleophile in the as the nucleophile in the reaction.reaction.

Cyclization of MonosaccharidesCyclization of Monosaccharides Notice that two different Notice that two different

stereochemical outcomes are stereochemical outcomes are possible, at the new chiral possible, at the new chiral center that is generated (the center that is generated (the hemiacetal). hemiacetal).

The hydroxyl group can be The hydroxyl group can be on the same side (cis) of the on the same side (cis) of the ring as the CHring as the CH22OH moiety OH moiety (beta configuration), or it (beta configuration), or it can be on the opposite side can be on the opposite side (trans) of the ring as the (trans) of the ring as the CHCH22OH moiety (alpha OH moiety (alpha configuration).configuration).

Notice the formal names for Notice the formal names for each of the two possible each of the two possible configurationsconfigurations..

D sugar ring structures form and reform so there is an intra-conversion between the and ß form. This is called mutarotation. Mutorotation occurs spontaneously or with the help of an enzyme (generally called a mutase)

The hemi groups are ordinarily unstable and revert back to the straight chain form

In solution: D-glucose (0.02%) -D Glucopyranoside (37%) and ß-D glucopyranoside (64%) less than 1% of the furans

pyranose and furanose are the basis for nomenclature; glucose refers to the mixtures of the different forms.

Beta form - OH above plane of ring Alpha form - OH below plane of ring

Reducing sugars - a reduction reaction at the aldehyde or ketone groups of the sugar molecules. As sugar is being oxidized, something else is being reduced:Only those anomeric carbons that can mutorotate are available for reduction. ie. disaccarides only contain 1 reducing sugar

Reactions of monosaccharidesReactions of monosaccharides

Formation of a carboxylic acid from an Formation of a carboxylic acid from an aldehyde is a 2-electron oxidation. aldehyde is a 2-electron oxidation.

Notice that the sugar acts as the reductant Notice that the sugar acts as the reductant of copperof copper. Copper is reduced from the +2 . Copper is reduced from the +2 state to the +1 state; however, the sugar state to the +1 state; however, the sugar is oxidized by 2 electrons. is oxidized by 2 electrons.

In the presence of Benedict’s reagent In the presence of Benedict’s reagent (sodium citrate, sodium carbonate, and (sodium citrate, sodium carbonate, and copper sulfate, reducing sugars will copper sulfate, reducing sugars will produce a brick-red precipitate of cuprous produce a brick-red precipitate of cuprous oxide.oxide.

There are enzymatic methods that can be There are enzymatic methods that can be used to quantify reducing sugars such as used to quantify reducing sugars such as glucose, which forms the basis of blood glucose, which forms the basis of blood sugar detection by diabetics.sugar detection by diabetics.

PhosphorylationPhosphorylation - can - can form anhydride form anhydride phosphoester bond.phosphoester bond.phosphorylation alters phosphorylation alters ionic character. ionic character. – Locks molecule in cell.Locks molecule in cell.– Nucleotides are Nucleotides are

phosphorylated (ATP, phosphorylated (ATP, GTP…)GTP…)

Reactions of monosaccharidesReactions of monosaccharides

Deoxy sugars - without oxygen common case - ribose RNA vs. DNA

Reactions of monosaccharidesReactions of monosaccharides

Amino sugars - Sugars with OH replaced by NH2. Amination usually occurs at C2 and often is acetylatedGlycosaminoglycans both amino and sulfated sugars.Heparin inhibits action of thrombin in blood clotting

- sugars as this will often have added C chains (acylated), sulfur groups (sulfanated) and aminated

Reactions of monosaccharidesReactions of monosaccharides

Important monosaccharides Glucose - preferred source of energy for brain

cells and cells without mitochondria Fructose - ketose, 2x as sweet as sucrose. Sperm

use this as major sugar/energy source for motility

Galactose - important for lacotose and glycolipid production

galactosemia - genetic disorder in galactose metabolism leads to accumulation of galactose-1-phosphate in liver results in liver damage. Another version of the disease results due to lack of galactose metabolism. Galactose concentration builds up in blood leading to cataracts.

- Can result in severe mental retardation. Identification and galactose free diet helps

Modification of monosaccharidesModification of monosaccharides A A uronic aciduronic acid is a sugar acid with both a is a sugar acid with both a

carbonyl and a carboxylic acid function. carbonyl and a carboxylic acid function.

It is best thought of as a sugar in which It is best thought of as a sugar in which the terminal carbon's hydroxyl function the terminal carbon's hydroxyl function has been oxidized to a carboxylic acid has been oxidized to a carboxylic acid

Some of these compounds have Some of these compounds have important biochemical functions; for important biochemical functions; for example, many wastes in the human example, many wastes in the human body are excreted in the urine as their body are excreted in the urine as their glucuronate salts glucuronate salts

Yes – peeing on plants is good for Yes – peeing on plants is good for them!!!!!!!!!them!!!!!!!!!

D-glucose

-D-glucuronic acid

Disaccharide NomenclatureDisaccharide Nomenclature When named, structures are considered to When named, structures are considered to

have their reducing ends on the right. have their reducing ends on the right. Locate the reducing ends of the structures Locate the reducing ends of the structures on the left if appropriate.on the left if appropriate.

The configuration of the anomeric carbon The configuration of the anomeric carbon joining the first monosaccharide unit to joining the first monosaccharide unit to the second is given (reading left to right). the second is given (reading left to right).

The non-reducing residue is named, and The non-reducing residue is named, and five-and six-membered ring structures are five-and six-membered ring structures are distinguished by using “furano” or distinguished by using “furano” or “pyrano” prefixes.“pyrano” prefixes.

Non-reducing disaccharides are named as glycosides rather Non-reducing disaccharides are named as glycosides rather than glycoses. Note that a double-headed arrow is used to than glycoses. Note that a double-headed arrow is used to denote sugars that are joined by their anomeric carbons, denote sugars that are joined by their anomeric carbons, AND, it is necessary to specifiy the stereochemistry at both AND, it is necessary to specifiy the stereochemistry at both anomeric carbons.anomeric carbons.

Disaccharide NomenclatureDisaccharide Nomenclature

The two carbons joined by the glycosidic The two carbons joined by the glycosidic bond are indicated in parentheses, with bond are indicated in parentheses, with an arrow connecting the two numbers.an arrow connecting the two numbers.

The second residue is then named.The second residue is then named.

If there are subsequent residues, the If there are subsequent residues, the subsequent glycosidic bonds are subsequent glycosidic bonds are described by the same conventions.described by the same conventions.

Non-reducing disaccharides are named as glycosides rather Non-reducing disaccharides are named as glycosides rather than glycoses. Note that a double-headed arrow is used to than glycoses. Note that a double-headed arrow is used to denote sugars that are joined by their anomeric carbons, denote sugars that are joined by their anomeric carbons, AND, it is necessary to specifiy the stereochemistry at both AND, it is necessary to specifiy the stereochemistry at both anomeric carbons.anomeric carbons.

– sucrose = table sugar - glucose and fructose (alpha linkage)

– lactose = milk sugar - galactose and glucose (beta linkage)

Maltose - malt sugar, from breakdown of starch - 2 glucoses

Important DisaccharidesImportant Disaccharides

Lactose intolerance inability to metabolize lactoseinability to metabolize lactose

lack of the required lack of the required enzyme lactase in the digestive enzyme lactase in the digestive system.system.

estimated that 75% of adults estimated that 75% of adults worldwide show some decrease in worldwide show some decrease in lactase activity during adulthood.lactase activity during adulthood.

The frequency of decreased lactase The frequency of decreased lactase activity ranges from as little as 5% in activity ranges from as little as 5% in northern Europe, up to 71% for Sicily, northern Europe, up to 71% for Sicily, to more than 90% in some African to more than 90% in some African and Asian countriesand Asian countries

Lactose intolerance Disaccharides cannot be absorbed Disaccharides cannot be absorbed

through the wall of the small intestine through the wall of the small intestine into the bloodstreaminto the bloodstream

so in the so in the absenceabsence of  of lactaselactase lactose present in ingested dairy lactose present in ingested dairy

products remains uncleaved and products remains uncleaved and passes intact into the colon.passes intact into the colon.

Remember that there are bacteria Remember that there are bacteria in the human digestive system!in the human digestive system!

Remember the LAC operon?Remember the LAC operon?

Lactase Part of the Part of the β-galactosidaseβ-galactosidase family of enzymes, is a glycoside  family of enzymes, is a glycoside

hydrolase involved in the hydrolysis of hydrolase involved in the hydrolysis of the disaccharide lactose into the disaccharide lactose into constituent galactose and glucose monomers. constituent galactose and glucose monomers.

Lactase is present predominantly along the brush Lactase is present predominantly along the brush border membrane of the differentiated enterocytes lining border membrane of the differentiated enterocytes lining the villi of the small intestine.the villi of the small intestine.

The LAC operonThe LAC operon

beta-galactosidase:beta-galactosidase: This enzyme hydrolyzes the bond This enzyme hydrolyzes the bond

between the two sugars, glucose and between the two sugars, glucose and galactose. galactose.

It is coded for by the gene LacZ.It is coded for by the gene LacZ.

Lactose Permease:Lactose Permease: This enzyme spans the cell This enzyme spans the cell

membrane and brings lactose into membrane and brings lactose into the cell from the outside the cell from the outside environment. The membrane is environment. The membrane is otherwise essentially impermeable to otherwise essentially impermeable to lactose. lactose. It is coded for by the gene LacY.It is coded for by the gene LacY.

Thiogalactoside transacetylase:Thiogalactoside transacetylase: The function of this enzyme is not The function of this enzyme is not

known. known. It is coded for by the gene LacA. It is coded for by the gene LacA.

Lactose intolerance The operons of enteric bacteria quickly The operons of enteric bacteria quickly

switch over to lactose metabolism, and switch over to lactose metabolism, and results in results in in vivoin vivo fermentation.  fermentation. – produces copious amounts of gas (a produces copious amounts of gas (a

mixture of hydrogen, carbon mixture of hydrogen, carbon dioxide, and methane). dioxide, and methane).

This, in turn, may cause a range of This, in turn, may cause a range of abdominal symptoms, including abdominal symptoms, including stomach cramps, nausea, bloating, acistomach cramps, nausea, bloating, acid reflux and flatulence. d reflux and flatulence.

In addition, as with other unabsorbed In addition, as with other unabsorbed sugars (such as sorbitol, mannitol, sugars (such as sorbitol, mannitol, and xylitol), the presence of lactose and xylitol), the presence of lactose and its fermentation products raises and its fermentation products raises the osmotic pressure of the the osmotic pressure of the colon contents.colon contents.

Lactose intolerance SymptomsSymptoms

Abdominal bloatingAbdominal bloating Abdominal crampsAbdominal cramps DiarrheaDiarrhea Floating stoolsFloating stools Foul-smelling stoolsFoul-smelling stools Gas (flatulence)Gas (flatulence) MalnutritionMalnutrition NauseaNausea Slow growthSlow growth Weight lossWeight loss

Lactose intolerance Most people with low lactase levels can Most people with low lactase levels can

tolerate 2 - 4 ounces of milk at one time (up tolerate 2 - 4 ounces of milk at one time (up to one-half cup). Larger (8 oz.) servings may to one-half cup). Larger (8 oz.) servings may cause problems for people with some cause problems for people with some amount of milk intolerance. amount of milk intolerance.

These milk products may be easier These milk products may be easier to digest:to digest:

Buttermilk and cheesesButtermilk and cheeses (they have less lactose (they have less lactose than milk)than milk)

Fermented milk productsFermented milk products, such as yogurt, such as yogurt Goat's milkGoat's milk (but drink it with meals, and make (but drink it with meals, and make

sure it is supplemented with essential amino acids sure it is supplemented with essential amino acids and vitamins if you give it to children)and vitamins if you give it to children)

Ice cream, milkshakes, and aged or hard Ice cream, milkshakes, and aged or hard cheesescheeses

Lactose-free milk and milk productsLactose-free milk and milk products Lactase-treated cow's milkLactase-treated cow's milk for older children for older children

and adultsand adults Soy formulasSoy formulas for infants younger than 2 years for infants younger than 2 years Soy or rice milkSoy or rice milk for toddlers for toddlers

Sucralose zero-calorie artificial sweetener

Approximately 600 times as sweet as sucrose

It is stable under heat and over a broad range of pH conditions

Belongs to a class of compounds known as organochlorides (or chlorocarbons). Some organochlorides, particularly those that accumulate in fatty tissues, are toxic to plants or animals, including humans.

Sucralose, however, is not known to be toxic in small quantities and is extremely insoluble in fat; it cannot accumulate in fat like chlorinated hydrocarbons.

In addition, sucralose does not break down or dechlorinate

Sucralose Some concern has been raised about

the effect of sucralose on the thymus.

 Two studies on rats, both of which found "a significant decrease in mean thymus weight" at high doses.

The sucralose dose which caused the effects was 3000 mg/kg/day for 28 days.

For a 150 lb (68.2 kg) human, this would mean an intake of nearly 205 grams of sucralose a day, which is equivalent to more than 17,200 individual Splenda packets/day for approximately one month

Important Polysaccharides:

Starch - energy reservoir in plants - made of two polysaccharides

Amylose -long unbranched glucose (1,4) with open reducing end large tight helical forms. Test by iodination..

Important Polysaccharides:Starch - energy reservoir in plants - made of two polysaccharides

– Amylose -long unbranched glucose (1,4) with open reducing end large tight helical forms. Test by iodination.

– Amylopectin - polymer of (1,4) and (1,6) branches. Not helical.

Glycogen - storage of carbohydrates in vertebrates greatest conc. in muscles and liver.

Similar to amylopectin with more branch points - takes up less space

CelluloseCellulose Linear glucan chains of Linear glucan chains of

unbranched (1-4)-unbranched (1-4)--linked--linked-D-glucose in which every D-glucose in which every other glucose residue is other glucose residue is rotated 180° with respect to rotated 180° with respect to its two neighbors and its two neighbors and contrasts with other glucan contrasts with other glucan polymers such as:polymers such as:

starch (1-4-starch (1-4--glucan) -glucan) callose (1-3-callose (1-3--glucan). -glucan).

CelluloseCellulose

This means that cellobiose, and not glucose, is the basic repeating This means that cellobiose, and not glucose, is the basic repeating unit of the cellulose molecule. Groups of 30 to 40 of these chains unit of the cellulose molecule. Groups of 30 to 40 of these chains laterally hydrogen-bond to form crystalline or para-crystalline laterally hydrogen-bond to form crystalline or para-crystalline microfibrils.microfibrils.

Chitin is a linear homopolysaccharide composed of N-Chitin is a linear homopolysaccharide composed of N-acetylglucosamine residues in acetylglucosamine residues in linkages. linkages.

Chitin differs chemically from cellulose only in the acetylated Chitin differs chemically from cellulose only in the acetylated amino substituent at carbon 2.amino substituent at carbon 2.

It forms extended fibers that are similar to those of cellulose, It forms extended fibers that are similar to those of cellulose, and is found principally in hard exoskeletons of arthropods.and is found principally in hard exoskeletons of arthropods.

Also occurs naturally in both parallel and antiparallel Also occurs naturally in both parallel and antiparallel stacking arrangements. stacking arrangements.

Chitin

Glycoproteins proteins that contain oligosaccharide chains covalently

attached to polypeptide side-chains.

The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. – In proteins that have segments extending extracellularly,

the extracellular segments are often glycosylated.

Glycoproteins are often important integral membrane proteins, where they play a role in cell-cell interactions.

Glycoproteins also occur in the cytosol, but their functions and the pathways producing these modifications in this compartment are less well-understood

Glycoproteins There are two types of

glycoproteins:

In N-glycosylation , the addition of sugar chains can happen at the amide nitrogen on the side chain of  asparagine.

In O-glycosylation, the addition of sugar chains can happen on the hydroxyl oxygen on the side chain of hydroxylysine, hydroxyproline, serine, or threonine.

asparagine

hydroxyproline

Glycoproteins The principal sugars found

in human glycoproteins

β-D-Glucose Glc β-D-Galactose Gal β-D-Mannose Man α-L-Fucose Fuc N-Acetylgalactosamine GalNAc N-Acetylglucosamine GlcNAc N-Acetylneuraminic acid

NeuNAc Xylose Xyl

Glycoproteins

examples of glycoproteins found in the body

Mucins secreted in the mucus of the respiratory

and digestive tracts. The sugars attached to mucins give them considerable water-holding capacity and also make them resistant to proteolysis by digestive enzymes.

In the immune system

white blood cell recognition molecules such as antibodies which interact directly with antigens

molecules of the major histocompatibility complex (or MHC), which are expressed on the surface of cells and interact with T cells as part of the adaptive immune response.

examples of glycoproteins found in the body glycoprotein IIb/IIIa

– an integrin found on platelets that is required for normal platelet aggregation and adherence to the endothelium.

The zona pellucida– which surrounds the oocyte, and is

important for sperm-egg interaction.

connective tissue. – These help bind together the fibers,

cells, and ground substance of connective tissue. They may also help components of the tissue bind to inorganic substances, such as calcium in bone.

Glycoprotein-41 (gp41) and glycoprotein-120 (gp120)

– HIV viral coat proteins.

examples of glycoproteins found in the body

Hormones that are glycoproteins include:

Follicle-stimulating hormone– Stimulates the follicle to

produce estrogen

Luteinizing hormone– Stimulates the corpus leuteum

to produce progesterone.

Thyroid-stimulating hormone

Human chorionic gonadotropin– maintains the corpus luteum and

allows the production of progesterone and estrogen until the placenta takes over this task

The End.

Any Questions?