Carbohydrate

Lactose is a disaccharide found in milk. It consists of 

a   molecule   of D-galactose and   a   molecule   of D-

glucose bonded by beta-1-4 glycosidic linkage. It has 

a formula of C12H22O11.

A carbohydrate is   an organic   compound that 

consists   only   of carbon,hydrogen,   and oxygen, 

usually with a hydrogen:oxygen atom ratio of 2:1 (as 

in water);   in   other   words,   with   the   empirical 

formula Cm(H2O)n.   (Some   exceptions   exist;   for 

example, deoxyribose, a component of DNA, has the 

empirical   formula  C5H10O4.)   Carbohydrates   are  not 

technically hydrates of carbon. Structurally it is more 

accurate   to   view   them   as polyhydroxy 

aldehydes and ketones.

The term is most common in biochemistry, where it 

is   a   synonym   ofsaccharide.   The   carbohydrates 

(saccharides)   are   divided   into   four   chemical 

groupings: monosaccharides, disaccharides, oligosac

charides,   andpolysaccharides.   In   general,   the 

monosaccharides   and   disaccharides,   which   are 

smaller (lower molecular weight) carbohydrates, are 

commonly   referred   to   as sugars.[1] The 

word saccharide comes   from 

the Greekword σάκχαρον (sákkharon),   meaning 

"sugar".   While   the   scientific   nomenclature   of 

carbohydrates   is   complex,   the   names   of   the 

monosaccharides and disaccharides very often end 

in   the   suffix -ose.   For   example, blood   sugar is   the 

monosaccharide glucose,   table   sugar   is   the 

disaccharide sucrose,   and   milk   sugar   is   the 

disaccharide lactose (see illustration).

Carbohydrates   perform   numerous   roles   in   living 

organisms.   Polysaccharides   serve   for   the   storage 

of energy (e.g., starch and glycogen),   and   as 

structural   components   (e.g., cellulose in   plants 

and chitin in   arthropods).   The   5-carbon 

monosaccharide ribose is   an   important   component 

of coenzymes (e.g., ATP, FAD,   and NAD)   and   the 

backbone   of   the   genetic  molecule   known   as RNA. 

The   relateddeoxyribose is   a   component   of DNA. 

Saccharides and their derivatives include many other 

important biomolecules that   play   key   roles   in 

the immune   system, fertilization, 

preventing pathogenesis, blood   clotting, 

and development.[2]

In food science and  in many  informal  contexts,  the 

term   carbohydrate   often   means   any food that   is 

particularly   rich   in   the   complex 

carbohydrate starch (such   as cereals, bread, 

and pasta)   or   simple   carbohydrates,   such 

as sugar (found in candy, jams, and desserts).

[edit]Structure

Formerly   the   name   "carbohydrate"   was   used 

in chemistry for   any   compound   with   the   formula 

Cm (H2O) n.  Following this  definition,  some chemists 

considered formaldehyde (CH2O) to be the simplest 

carbohydrate,[3] while   others   claimed   that   title 

for glycolaldehyde.[4]Today   the   term   is   generally 

understood   in   the   biochemistry   sense,   which 

excludes compounds with only one or two carbons.

Natural   saccharides   are   generally   built   of   simple 

carbohydrates   called monosaccharides with   general 

formula (CH2O)n where n is three or more. A typical 

monosaccharide has the structure H-(CHOH)x(C=O)-

(CHOH)y-H,   that   is,   an aldehyde or ketone with 

many hydroxylgroups   added,   usually   one   on 

each carbon atom that is not part of the aldehyde or 

ketone functional   group.   Examples   of 

monosaccharides   are glucose, fructose, 

and glyceraldehydes.   However,   some   biological 

substances commonly called "monosaccharides" do 

not  conform to  this   formula  (e.g., uronic  acids and 

deoxy-sugars   such  as fucose),   and   there   are  many 

chemicals that do conform to this formula but are 

not   considered   to   be   monosaccharides   (e.g., 

formaldehyde CH2O and inositol (CH2O)6).[5]

The open-chain form   of   a   monosaccharide   often 

coexists   with   a closed   ring   form where 

the aldehyde/ketone carbonyl group   carbon   (C=O) 

and hydroxyl group   (-OH)   react   forming 

a hemiacetal with a new C-O-C bridge.

Monosaccharides can be linked together into what 

are   called polysaccharides (or oligosaccharides)   in  a 

large variety of  ways.  Many carbohydrates  contain 

one   or  more  modified  monosaccharide   units   that 

have had one or more groups replaced or removed. 

For example, deoxyribose, a component of DNA, is a 

modified   version   of ribose; chitin is   composed   of 

repeating units of N-acetyl glucosamine, a nitrogen-

containing form of glucose.

[edit]Monosaccharides

Monosaccharide

D-glucose is   an   aldohexose   with   the   formula 

(C·H2O)6. The red atoms highlight thealdehyde group, 

and   the   blue   atoms   highlight   theasymmetric 

centerfurthest from the aldehyde; because this -OH 

is on the right of theFischer projection, this  is  a D 

sugar.

Monosaccharides are the simplest carbohydrates in 

that   they   cannot   be hydrolyzed to   smaller 

carbohydrates. They are aldehydes or ketones with 

two or more hydroxyl groups. The general chemical 

formula of   an   unmodified   monosaccharide   is 

(C•H2O) n,   literally   a   "carbon   hydrate." 

Monosaccharides   are   important   fuel  molecules   as 

well as building blocks for nucleic acids. The smallest 

monosaccharides,   for   which   n   =   3,   are 

dihydroxyacetone and D- and L-glyceraldehydes.

[edit]Classification of monosaccharides

The α and β anomers of glucose. Note the position of 

the hydroxyl group (red or green) on the anomeric 

carbon relative to the CH2OH group bound to carbon 

5: they are either on the opposite sides (α), or the 

same side (β).

Monosaccharides   are   classified   according   to   three 

different   characteristics:   the   placement   of 

its carbonyl group,   the   number   ofcarbon atoms   it 

contains,  and  its chiral handedness.   If   the  carbonyl 

group   is   an aldehyde,   the   monosaccharide   is 

an aldose;   if   the   carbonyl   group   is   a ketone,   the 

monosaccharide  is  a ketose.  Monosaccharides  with 

three   carbon   atoms   are   called trioses,   those  with 

four are calledtetroses, five are called pentoses, six 

are hexoses,   and   so   on.[6] These   two   systems   of 

classification   are   often   combined.   For 

example, glucoseis   an aldohexose (a   six-carbon 

aldehyde), ribose is   an aldopentose (a   five-carbon 

aldehyde), and fructose is a ketohexose (a six-carbon 

ketone).

Each   carbon  atom bearing   a hydroxyl   group (-OH), 

with   the   exception   of   the   first   and   last   carbons, 

are asymmetric,   making   them stereo   centerswith 

two possible configurations each (R or S). Because of 

this asymmetry,  a number of isomers may exist  for 

any given monosaccharide formula. The aldohexose 

D-glucose, for example, has the formula (C·H2O) 6, of 

which   all   but   two   of   its   six   carbons   atoms   are 

stereogenic,   making   D-glucose   one   of   24 =   16 

possible stereoisomers.   In   the   case 

of glyceraldehydes, an aldotriose, there is one pair of 

possible   stereoisomers,   which 

are enantiomers and epimers. 1,   3-

dihydroxyacetone, the ketose corresponding to the 

aldose   glyceraldehydes,   is   a   symmetric   molecule 

with no stereo centers). The assignment of D or L is 

made according to the orientation of the asymmetric 

carbon   furthest   from   the   carbonyl   group:   in   a 

standard Fischer projection if the hydroxyl group is 

on the right the molecule is a D sugar, otherwise it is 

an L sugar. The "D-" and "L-" prefixes should not be 

confused   with   "d-"   or   "l-",   which   indicate   the 

direction that the sugarrotates plane polarized light. 

This usage of "d-" and "l-" is no longer followed in 

carbohydrate chemistry.[7]

[edit]Ring-straight chain isomerism

Glucose can exist   in  both a  straight-chain  and ring 

form.

The  aldehyde  or   ketone   group  of   a   straight-chain 

monosaccharide will react reversibly with a hydroxyl 

group   on   a   different   carbon   atom   to   form 

a hemiacetal or hemiketal,   forming 

aheterocyclic ring  with   an   oxygen   bridge   between 

two carbon atoms. Rings with five and six atoms are 

called furanose and pyranose forms,   respectively, 

and exist in equilibrium with the straight-chain form.[8]

During   the  conversion   from straight-chain   form to 

the   cyclic   form,   the   carbon   atom   containing   the 

carbonyl   oxygen,   called   the anomeric   carbon, 

becomes   a   stereogenic   center   with   two   possible 

configurations: The oxygen atom may take a position 

either  above  or  below  the  plane  of   the   ring.   The 

resulting   possible   pair   of   stereoisomers   is 

called anomers.   In   the α anomer,   the   -OH 

substituent   on   the   anomeric   carbon   rests   on   the 

opposite side (trans) of the ring from the CH2OH side 

branch.  The  alternative   form,   in  which   the  CH2OH 

substituent  and  the  anomeric  hydroxyl  are  on   the 

same side (cis) of the plane of the ring, is called the β

anomer.

[edit]Use in living organisms

Monosaccharides   are   the   major   source   of   fuel 

for metabolism, being used both as an energy source 

(glucose  being   the  most   important   in  nature)  and 

in biosynthesis.   When   monosaccharides   are   not 

immediately  needed by  many  cells   they  are  often 

converted   to   more   space-efficient   forms, 

often polysaccharides.   In   many   animals,   including 

humans, this storage form is glycogen, especially in 

liver and muscle cells. In plants, starch is used for the 

same purpose.

[edit]Disaccharides

Sucrose,   also   known   as   table sugar,   is   a   common 

disaccharide.   It   is   composed   of   two 

monosaccharides: D-glucose (left)   and D-

fructose(right).

Main article: Disaccharide

Two   joined   monosaccharides   are   called 

a disaccharide and   these   are   the   simplest 

polysaccharides.   Examples 

include sucrose and lactose.   They  are   composed  of 

two   monosaccharide   units   bound   together   by 

a covalent bond known as a glycosidic linkageformed 

via  a dehydration   reaction,   resulting   in   the   loss  of 

a hydrogen atom   from   one   monosaccharide   and 

a hydroxyl   group from   the   other.   The formula of 

unmodified   disaccharides   is   C12H22O11.   Although 

there are numerous kinds of disaccharides, a handful 

of disaccharides are particularly notable.

Sucrose, pictured to the right, is the most abundant 

disaccharide,   and   the   main   form   in   which 

carbohydrates   are   transported   in plants.   It   is 

composed   of   one D-glucosemolecule   and   one D-

fructose molecule.   The systematic   name for 

sucrose, O-α-D-glucopyranosyl-(1→2)-D-

fructofuranoside, indicates four things:

Its monosaccharides: glucose and fructose

Their   ring   types:   glucose   is   a pyranose,   and 

fructose is a furanose

How they  are   linked  together:   the  oxygen on 

carbon number 1 (C1) of α-D-glucose is linked to 

the C2 of D-fructose.

The -oside suffix   indicates   that   the anomeric 

carbon of both monosaccharides participates in 

the glycosidic bond.

Lactose,   a   disaccharide   composed   of   one D-

galactose molecule   and   one D-glucose molecule, 

occurs  naturally   in  mammalian milk.  Thesystematic 

name for lactose is O-β-D-galactopyranosyl-(1→4)-D-

glucopyranose.   Other   notable   disaccharides 

include maltose (two   D-glucoses   linked   α-1,4)   and 

cellulobiose   (two   D-glucoses   linked   β-1,4). 

disaccharides can be classified into two types.They 

are reducing and non-reducing disaccahrides  if   the 

functional group is present in bonding with another 

sugar   unit   it   is   called   a   reducing   disaccharide   or 

biose.

[edit]Nutrition

Grain products: rich sources of carbohydrates

Foods  high   in   carbohydrate   include   fruits,   sweets, 

soft  drinks,   breads,   pastas,   beans,   potatoes,   bran, 

rice,   and   cereals.   Carbohydrates   are   a   common 

source  of  energy   in   living  organisms;  however,  no 

carbohydrate is an essential nutrient in humans.[9]

Carbohydrates are not necessary building blocks of 

other  molecules,   and   the   body   can   obtain   all   its 

energy   from   protein   and   fats.[10][11] The   brain   and 

neurons  generally  cannot  burn   fat   for  energy,  but 

use   glucose   or ketones.   Humans   can   synthesize 

some   glucose   (in   a   set   of   processes   known 

as gluconeogenesis) from specific amino acids, from 

the glycerolbackbone   in triglycerides and   in   some 

cases   from   fatty   acids.   Carbohydrate   and   protein 

contain 4 kilocalories per gram, while fats contain 9 

kilocalories per gram. In the case of protein, this is 

somewhat misleading as only some amino acids are 

usable for fuel.

Organisms  typically   cannot  metabolize  all   types  of 

carbohydrate   to   yield   energy.  Glucose   is   a   nearly 

universal   and   accessible   source   of   calories.  Many 

organisms   also   have   the   ability   to   metabolize 

other monosaccharides and Disaccharides,   though 

glucose is preferred. InEscherichia coli, for example, 

the lac operon will express enzymes for the digestion 

of lactose when it is present, but if both lactose and 

glucose   are   present   the lac operon   is   repressed, 

resulting   in   the   glucose   being   used   first 

(see: Diauxie). Polysaccharides are   also   common 

sources of energy. Many organisms can easily break 

down   starches   into   glucose,   however,   most 

organisms   cannot   metabolize   cellulose   or   other 

polysaccharides   like chitinand arabinoxylans.   These 

carbohydrates   types   can  be  metabolized  by   some 

bacteria   and   protists. Ruminants and termites,   for 

example,   use  microorganisms   to   process cellulose. 

Even though these complex carbohydrates are not 

very digestible, they may comprise important dietary 

elements   for   humans.   Called   dietary   fiber,   these 

carbohydrates   enhance   digestion   among   other 

benefits.[12]

Based on  the  effects  on   risk  of  heart  disease  and 

obesity,[13] the Institute   of   Medicine recommends 

that American and Canadian adults get between 45–

65%   of dietary   energy from   carbohydrates.[14] The Food and Agriculture Organization and World 

Health Organizationjointly recommend that national 

dietary   guidelines   set   a   goal   of   55–75%   of   total 

energy   from carbohydrates,   but  only   10%  directly 

from sugars (their term for simple carbohydrates).[15]

[edit]Classification

Historically   nutritionists   have   classified 

carbohydrates   as   either   simple   or   complex. 

However, the exact delineation of these categories is 

ambiguous.   Today,   simple   carbohydrate   typically 

refers   to monosaccharides and disaccharides and 

complex   carbohydrate 

meanspolysaccharides (and oligosaccharides). 

However,   the   term complex carbohydrate was  first 

used in slightly different context in the U.S. Senate 

Select   Committee   on   Nutrition   and   Human 

Needs publication Dietary Goals for the United

States (1977).   In   this  work,   complex   carbohydrate 

were defined as "fruit, vegetables and whole-grains".[16] Some nutritionists  use complex carbohydrate to 

refer to any sort of digestible saccharide present in a 

whole food, where fiber, vitamins and minerals are 

also found (as opposed to processed carbohydrates, 

which provide calories but few other nutrients).

Some   simple   carbohydrates   (e.g.   fructose)   are 

digested   very   slowly,   while   some   complex 

carbohydrates   (starches),   especially   if   processed, 

raise blood sugar rapidly. The speed of digestion is 

determined by a variety of factors  including which 

other   nutrients   are   consumed   with   the 

carbohydrate, how the food is prepared, individual 

differences in metabolism, and the chemistry of the 

carbohydrate.

The USDA's Dietary Guidelines for Americans

2010 call   for   moderate-   to   high-carbohydrate 

consumption from a balanced diet that includes six 

one-ounce servings of grain foods each day, at least 

half   from  whole   grain   sources   and   the   rest   from 

enriched.[17]

The glycemic   index   (GI) and glycemic   load concepts 

have been developed to characterize food behavior 

during   human   digestion.   They   rank   carbohydrate-

rich foods based on the rapidity and magnitude of 

their effect on blood glucose levels. Glycemic index is 

a measure of how quickly food glucose is absorbed, 

while   glycemic   load   is   a   measure   of   the   total 

absorbable   glucose   in   foods.   The insulin   index is   a 

similar, more recent classification method that ranks 

foods based on their effects on blood insulin levels, 

which are caused by glucose (or  starch)  and some 

amino acids in food.

 Glucose

Glucose is by far the most common carbohydrate and classified as a monosaccharide, an aldose, a hexose, and is a reducing sugar. It is also known as dextrose, because it is dextrorotatory (meaning that as an optical isomer is rotates plane polarized light to the right and also an origin for the D designation.

Glucose is also called blood sugar as it circulates in the blood at a concentration of 65-110 mg/dL (or 65-110 mg/100 ml) of blood.

Glucose is initially synthesized by chlorophyll in plants using carbon dioxide from the air and sunlight as an energy source. Glucose is further converted to starch for storage.

Click for larger image 

Ring Structure for Glucose:

Up until now we have been presenting the structure of glucose as a chain. In reality, an aqueous sugar solution contains only 0.02% of the glucose in the chain form, the majority of the structure is in the cyclic chair form.Since carbohydrates contain both alcohol and aldehyde or ketone functional groups, the straight-chain form is easily converted into the chair form - hemiacetal ring structure. Due to the tetrahedral geometry of carbons that ultimately make a 6 membered stable ring , the -OH on carbon #5 is converted into the ether linkage to close the ring with carbon #1. This makes a 6 member ring - five carbons and one oxygen.

Steps in the ring closure (hemiacetal synthesis):1. The electrons on the alcohol oxygen are used to bond the carbon #1 to make an ether (red oxygen atom).2. The hydrogen (green) is transferred to the carbonyl oxygen (green) to make a new alcohol group (green).

The chair structures are always written with the orientation depicted on the left to avoid confusion.

Hemiacetal Functional Group:

Carbon # 1 is now called the anomeric carbon and is the center of a hemiacetal functional group. A carbon that has both an ether oxygen and an alcohol group is a hemiacetal.

Open graphic of hemiacetal in a new window

Click for larger image 

 

Compare Alpha and Beta Glucose in the Chair Structures:

The position of the -OH group on the anomeric carbon (#1) is an important distinction for carbohydrate chemistry.

The Beta position is defined as the -OH being on the same side of the ring as the C # 6. In the chair structure this results in a horizontal projection.

The Alpha position is defined as the -OH being on the opposite side of the ring as the C # 6. In the chair structure this results in a downward projection.

The alpha and beta label is not applied to any other carbon - only the anomeric carbon, in this case # 1.

Compare Alpha and Beta Glucose- Chime in new window 

Compare Alpha and Beta Glucose in the Haworth Structures:

Open graphic of Haworth Structures in a new window

The Beta position is defined as the -OH being on the same side of the ring as the C # 6. In the Haworth structure this results in an upward projection.

The Alpha position is defined as the -OH being on the opposite side of the ring as the C # 6. In the Haworth structure this also results in a downward projection.

 Galactose

Galactose is more commonly found in the disaccharide, lactose or milk sugar. It is found as the monosaccharide in peas.

Galactose is classified as a monosaccharide, an aldose, a hexose, and is a reducing sugar.

Galactosemia - Genetic Enzyme Deficiency:

One baby out of every 18,000 is born with a genetic defect of not being able to utilize galactose. Since galactose is in milk as part of lactose, it will build up in the blood and urine. Undiagnosed it may lead to mental retardation, failure to grow, formation of cataracts, and in sever cases death by liver damage. The disorder is caused by a deficiency in one or more enzymes required to metabolize galactose.

The treatment for the disorder is to use a formula based upon the sugar sucrose rather than milk with lactose. The galactose free diet is critical only in infancy, since with maturation another enzyme is developed that can metabolize galactose.

Click for larger image 

Ring Structure for Galactose:

The chair form of galactose follows the same pattern as that for glucose.

Open graphic of glucose in a new window

Hemiacetal Functional Group:

The anomeric carbon is the center of a hemiacetal functional group. A carbon that has both an ether oxygen and an alcohol group is a hemiacetal.

Open graphic of hemiacetal in a new window

Which carbon in the structure on the left is the anomeric carbon?

Then check the answer from the drop down menu.

Compare Alpha and Beta Galactose in the Chair form (left graphic):

The Beta position is defined as the -OH being on the same side of the ring as the C # 6. In the chair structure this results in a horizontal projection,(Haworth - an upwards projection).

The Alpha position is defined as the -OH being on the opposite side of the ring as the C # 6. In the chair and Haworth structure this results in a downward projection.

Click for larger image 

 

Compare Glucose and Galactose in the Chair Structures:

The position of the -OH group on the carbon (#4) is the only distinction between glucose and galactose.

Glucose is defined as the -OH on C # 4 in a horizontal projection in the chair form, (down in the Haworth structure).

Galactose is defined as the -OH on C # 4 in a upward projection in the chair form,(also upward in the Haworth structure).

Both glucose and galactose may be either alpha or beta on the anomeric carbon, so this is not distinctive between them

Carbon # 1

 Fructose

Fructose is more commonly found together with glucose and sucrose in honey and fruit juices. Fructose, along with glucose are the monosaccharides found in disaccharide, sucrose.

Fructose is classified as a monosaccharide, the most important ketose sugar, a hexose, and is a reducing sugar.

An older common name for fructose is levulose, after its levorotatory property of rotating plane polarized light to the left (in contrast to glucose which is dextrorotatory).

Bees gather nectar from flowers which contains sucrose. They then use an enzyme to hydrolyze or break apart the sucrose into its component parts of glucose and fructose.

High Fructose Corn Syrup

Click for larger image 

Ring Structure for Fructose:

The chair form of fructose follows a similar pattern as that for glucose with a few exceptions. Since fructose has a ketone functional group, the ring closure occurs at carbon # 2. See the graphic on the left.

In the case of fructose a five membered ring is formed. The -OH on carbon #5 is converted into the ether linkage to close the ring with carbon #2. This makes a 5 member ring - four carbons and one oxygen.

Steps in the ring closure (hemiketal synthesis):1. The electrons on the alcohol oxygen are used to bond the carbon #2 to make an ether (red oxygen atom).2. The hydrogen (green) is transferred to the carbonyl oxygen (green) to make a new alcohol group (green).

The ring structure is written with the orientation depicted on the left for the monosaccharide and is consistent with

the way the glucose is depicted.

Hemiketal Functional Group:

The anomeric carbon is the center of a hemiketal functional group. A carbon that has both an ether oxygen and an alcohol group (and is attached to two other carbons is a hemiketal.

Open graphic of hemiacetal/hemiketal in a new window

Which carbon in the structure on the left is the anomeric carbon?Then check the answer from the drop down menu.

Compare Alpha and Beta Fructose:

The Beta position is defined as the -OH being on the same side of the ring as the C # 6. In the ring structure this results in a upwards projection for the -OH on carbon # 2.

The Alpha position is defined as the -OH being on the opposite side of the ring as the C # 6. In the ring structure this results in a downward projection for the -OH on carbon # 2.

The alpha and beta label is not applied to any other carbon - only the anomeric carbon, in this case # 2.

Open graphic of Alpha/Beta Fructose in a new window

Compare Alpha and Beta Fructose - Chime in new window

Carbon # 2

Click for larger image 

 

Compare Glucose and Fructose in the Chair Structures:

The six member ring and the position of the -OH group on the carbon (#4) identifies glucose from the -OH on C # 4 in a down projection in the Haworth structure).

Fructose is recognized by having a five member ring and having six carbons, a hexose.

Both glucose and fructose may be either alpha or beta on the anomeric carbon, so this is not distinctive between them

 Maltose

Maltose is made from two glucose units:

Maltose or malt sugar is the least common disaccharide in nature. It is present in germinating grain, in a small proportion in corn syrup, and forms on the partial hydrolysis of starch. It is a reducing sugar.

The two glucose units are joined by an acetal oxygen bridge in the alpha orientation. To recognize glucose look for the down or horizontal projection of the -OH on carbon # 4. See details on the galactose page towards the bottom.

Malted Barley:

Beer is made from four basic building blocks: water, malted barley, and hops.

Barley, a basic cereal grain, is low in gluten, and is not particularly good for milling into flour for use in products such as bread. Barley is the preferred grain to make beer. The barley grains must be "malted" before they can be used in the

brewing process.

Malting is a process of bringing grain to the point of its highest possible starch content by allowing it to begin to sprout roots and take the first step to becoming a photosynthesizing plant.

At the point when the maximum starch content is reached, the seed growth is stopped by heating the grain to a temperature that stops growth but allows an important natural enzyme diastase to remain active. Barley, once "malted" is very high in the type of starches that an enzyme called diastase (found naturally on the surface of the grain, just under the husk) can convert starch quite easily into the disaccharide called Maltose. This sugar is then fermented or metabolized by the yeasts to create carbon dioxide and ethyl alcohol.

Adapted from: Beer Basics

 

Acetal Functional Group:

Carbon # 1 (red on left) is called the anomeric carbon and is the center of an acetal functional group. A carbon that has two ether oxygens attached is an acetal.

The Alpha position is defined as the ether oxygen being on the opposite side of the ring as the C # 6. In the chair structure this results in a downward projection. This is the same definition as the -OH in a hemiacetal.

Open graphic of hemiacetal in a new window

Maltose - Chime in new window

Hydrolysis of Starch:

In the hydrolysis of any di- or poly saccharide, a water molecule helps to break the acetal bond as shown in red. The acetal bond is broken, the H from the water is added to the oxygen on one glucose.

The -OH is then added to the carbon on the other glucose. In this case the diastase enzyme is very specific and cuts the starch chain in units of two glucose which happens to be maltose.

 Lactose

Lactose is made from galactose and glucose units:

Lactose or milk sugar occurs in the milk of mammals - 4-6% in cow's milk and 5-8% in human milk. It is also a by product in the the manufacture of cheese.

The galactose and glucose units are joined by an acetal oxygen bridge in thebeta orientation. To recognize galactose look for the upward projection of the -OH on carbon # 4. See details on the galactose page towards the bottom.

Lactose intolerance:

Lactose intolerance is the inability to digest significant amounts of lactose, the predominant sugar of milk. This inability results from a shortage of the enzyme lactase, which is normally produced by the cells that line the small intestine. Lactase breaks down the lactose, milk sugar, into glucose and galactose that can then be absorbed into the bloodstream. When there is not

enough lactase to digest the amount of lactose consumed, produce some uncomfortable symptoms. Some adults have low levels of lactase. This leads to lactose intolerance. The ingested lactose is not absorbed in the small intestine, but instead is fermented by bacteria in the large intestine, producing uncomfortable volumes of carbon dioxide gas. While not all persons deficient in lactase have symptoms, those who do are considered to be lactose intolerant.

Common symptoms include nausea, cramps, bloating, gas, and diarrhea, which begin about 30 minutes to 2 hours after eating or drinking foods containing lactose. The severity of symptoms varies depending on the amount of lactose each individual can tolerate.

Fortunately, lactose intolerance is relatively easy to treat by controlling the diet. No cure or treatment exists to improve the body's ability to produce lactase. Young children with lactase deficiency should not eat any foods containing lactose. Most older children and adults need not avoid lactose completely, but individuals differ in the amounts and types of foods they can handle. Dietary control of lactose intolerance depends on each person's learning through trial and error how much lactose he or she can handle.

Adapted from: Lactose Intolerance

Open graphic of hydrolysis of lactose in a new window

 

Acetal Functional Group:

Carbon # 1 (red on left) is called the anomeric carbon and is the center of an acetal functional group. A carbon that has two ether oxygens attached is an acetal.

The Beta position is defined as the ether oxygen being on the same side of the ring as the C # 6. In the chair structure this results in a horizontal or up projection. This is the same definition as the -OH in a hemiacetal.

Open graphic of hemiacetal in a new window

Lactose - Chime in new window

Compare Lactose and Maltose Acetals:

The position of the oxygen in the acetal on the anomeric carbon (#1) is an important distinction for disaccharide chemistry.

Lactose has a beta acetal. The Beta position is defined as the oxygen in the acetal being on the same side of the ring as the C # 6. In the chair structure this results in a horizontal projection.

Maltose has an alpha acetal. The Alpha position is defined as the oxygen in the acetal being on the opposite side of the ring as the C # 6. In the chair structure this results in a downward projection.

The alpha and beta acetal label is not applied to any other carbon - only the anomeric carbon of the left monosaccharide, in this case # 1 (red).

 

Recognize galactose and glucose:

To further identify lactose and maltose, identify the presence of galactose in lactose in the left most structure by the upward -OH on the carbon # 4.

Identify glucose in maltose in the left most structure by the horizontal -OH on the carbon # 4.

Sucrose is made from glucose and fructose units:

Sucrose or table sugar is obtained from sugar cane or sugar beets.

The glucose and fructose units are joined by an acetal oxygen bridge in thealpha orientation. The structure is easy to recognize because it contains the six member ring of glucose and the five member ring of fructose.

To recognize glucose look for the horizontal projection of the -OH on carbon # 4. See details on the galactose page towards the bottom.

The alpha acetal is is really part of a double acetal, since the two monosaccharides are joined at the hemiacetal of glucose and the hemiketal of the fructose. There are no hemiacetals remaining in the sucrose and therefore sucrose is a non-reducing sugar.

Sugar and Tooth Decay

Sugar Processing:

Sugar or more specifically sucrose is a carbohydrate that occurs naturally in every fruit and vegetable. It is the major product of photosynthesis, the process by which plants transform the sun's energy into food. Sugar occurs in greatest quantities in sugar cane and sugar beets from which it is separated for commercial use.

In the first stage of processing the

natural sugar stored in the cane stalk or beet root is separated from the rest of the plant material by physical methods. For sugar cane, this is accomplished by: a) pressing the cane to extract the juice containing the sugar b) boiling the juice until it begins to thicken and sugar begins to crystallize c) spinning the sugar crystals in a centrifuge to remove the syrup, producing raw sugar; the raw sugar still contains many impuritiesd) shipping the raw sugar to a refinery where it is washed and filtered to remove remaining non-sugar ingredients and color e) crystallizing, drying and packaging the refined sugar.

Beet sugar processing is similar, but it is done in one continuous process without the raw sugar stage. The sugar beets are washed, sliced and soaked in hot water to separate the sugar-containing juice from the beet fiber. The sugar-laden juice is purified, filtered, concentrated and dried in a series of steps similar to cane sugar processing.

Adapted from: Sugar Facts

 

Acetal Functional Group:

Carbon # 1 (red on left) is called the anomeric carbon and is the center of an acetal functional group. A carbon that has two ether oxygens attached is an acetal.

The Alpha position is defined as the ether oxygen being on the opposite side of the ring as the C # 6. In the chair structure this results in a down projection. This is the same definition as the -OH in a hemiacetal.

A second acetal grouping is defined by the green atoms. This result because the the formation reaction of the disaccharide is between the hemiacetal of glucose and the hemiketal of the fructose.

Open graphic of hemiacetal in a new window

Sucrose - Chime in new window

Invert Sugar:

When sucrose is hydrolyzed it forms a 1:1 mixture of glucose and fructose. This mixture is the main ingredient in honey. It is called invert sugar because the angle of the specific rotation of the plain polarized light changes from a positive to a negative value due to the presence of the optical isomers of the mixture of glucose and fructose sugars. 

Hydrolysis of Sucrose:

In the hydrolysis of any di- or poly saccharide, a water molecule helps to break the acetal bond as shown in red. The acetal bond is broken, the H from the water is added to the oxygen on the glucose.

The -OH is then added to the carbon on the fructose.

 

Click for larger image 

 StarchPolysaccharides are carbohydrate polymers consisting of tens to hundreds to several thousand monosaccharide units. All of the common polysaccharides contain glucose as the monosaccharide unit. Polysaccharides are synthesized by plants, animals, and humans to be stored for food, structural support, or metabolized for energy.

Starch can be separated into two fractions--amylose and amylopectin. Natural starches are mixtures of amylose (10-20%) and amylopectin (80-90%).

Amylose forms a colloidal dispersion

in hot water whereas amylopectin is completely insoluble. The structure of amylose consists of long polymer chains of glucose units connected by an alpha acetal linkage. The graphic on the left shows a very small portion of an amylose chain. All of the monomer units are alpha -D-glucose, and all the alpha acetal links connect C # 1 of one glucose to C # 4 of the next glucose.

Starch - Amylose - Chime in new window

Acetal Functional Group:

Carbon # 1 is called the anomeric carbon and is the center of an acetal functional group. A carbon that has two ether oxygens attached is an acetal.

The Alpha position is defined as the ether oxygen being on the opposite side of the ring as the C # 6. In the chair structure this results in a downward projection. This is the same definition as the -OH in a hemiacetal.

Open graphic of hemiacetal in a new window

Click for larger image 

Starch Coil or Spiral Structure:

As a result of the bond angles in the alpha acetal linkage, amylose actually forms a spiral much like a coiled spring.

Amylose is responsible for the formation of a deep bluecolor in the presence of iodine. The iodine molecule slips inside of the amylose coil.

 

Starch Coil - Chime in new window

Click for larger image 

Amylopectin:

The graphic on the left shows very small portion of an amylopectin-type structure showing two branch points [drawn closer together than they should be]. The acetal linkages are alpha connecting C # 1 of one glucose to C # 4 of the next glucose.

The branches are formed by linking C # 1 to a C # 6 through an acetal linkages. Amylopectin has 12-20 glucose units between the branches. Natural starches are mixtures of amylose and amylopectin.

In glycogen, the branches occur at intervals of 8-10 glucose units, while in amylopectin the branches are separated by 10-12 glucose units.

 CellulosePolysaccharides are carbohydrate polymers consisting of tens to hundreds to several thousand monosaccharide units. All of the common polysaccharides contain glucose as the monosaccharide unit. Polysaccharides are synthesized by plants, animals, and humans to be stored for food, structural support, or metabolized for energy.

Cellulose:

The major component in the rigid cell walls in plants is cellulose. Cellulose is a linear polysaccharide polymer with many glucose monosaccharide units. The acetal linkage is beta which makes it different from starch. This peculiar difference in acetal linkages results in a major difference in digestibility in humans. Humans are unable to digest cellulose because the appropriate enzymes to breakdown the beta acetal linkages are lacking. (More on enzyme digestion in a later chapter.) Undigestible cellulose is the fiber which aids in the smooth working of the intestinal tract.

Animals such as cows, horses, sheep, goats, and termites have symbiotic bacteria in the intestinal tract. These symbiotic bacteria possess the necessary enzymes to digest cellulose in the GI tract. They have the required enzymes for the breakdown or hydrolysis of the cellulose; the animals do not, not even termites, have the correct enzymes. No vertebrate can digest cellulose directly.

Even though we cannot digest cellulose, we find many uses for it including: Wood for building; paper products; cotton, linen, and rayon for clothes; nitrocellulose for explosives; cellulose acetate for films.

The structure of cellulose consists of long polymer chains of glucose units connected by a beta acetal linkage. The graphic on the left shows a very small portion of a cellulose chain. All of the monomer units are beta-D-glucose, and all the beta acetal links connect C # 1 of one glucose to C # 4 of the next glucose.

Cellulose - Chime in new window

Acetal Functional Group:

Carbon # 1 is called the anomeric carbon and is the center of an acetal functional group. A carbon that has two ether oxygens attached is an acetal.

The Beta position is defined as the ether oxygen being on the same side of the ring as the C # 6. In the chair structure this results in a horizontal or up projection. This is the same definition as the -OH in a hemiacetal.

Open graphic of hemiacetal in a new window

Compare Cellulose and Starch Structures:

Cellulose: Beta glucose is the monomer unit in cellulose. As a result of the bond angles in the beta acetal linkage, cellulose is mostly a linear chain.

Starch: Alpha glucose is the monomer unit in starch. As a result of the bond angles in the alpha acetal linkage, starch-amylose actually forms a spiral much like a coiled spring.

 

Compare Starch and Cellulose - Chime in new window

Fiber in the Diet:

Dietary fiber is the component in food not broken down by digestive enzymes and secretions of the gastrointestinal tract. This fiber includes hemicelluloses, pectins, gums, mucilages, cellulose, (all carbohydrates) and lignin, the only non-carbohydrate component of dietary fiber.

High fiber diets cause increased stool size and may help prevent or cure constipation. Cereal fiber, especially bran, is most effective at increasing stool size while pectin has little effect. Lignin can be constipating.

Fiber may protect against the development of colon cancer, for populations consuming high fiber diets have a low incidence of this disease. The slow transit time (between eating and elimination) associated with a low fiber intake would allow more time for carcinogens present in the colon to initiate cancer. But constipated people do not have a higher incidence of colon cancer than fast eliminators, so fiber's role in colon cancer remains unclear.

Dietary fiber may limit cholesterol absorption by binding bile acids. High fiber diets lower serum cholesterol and may prevent cardiovascular disease. Some fibers, such as pectin and rolled oats, are more effective than others, such as wheat, at lowering serum cholesterol.

Dietary fiber is found only in plant foods such as fruits, vegetables, nuts, and grains. Whole wheat bread contains more fiber than white bread and apples contain more fiber than apple juice, which shows that processing food generally removes fiber.

Click for larger image 

 GlycogenPolysaccharides are carbohydrate polymers consisting of tens to hundreds to several thousand monosaccharide units. All of the common polysaccharides contain glucose as the monosaccharide unit. Polysaccharides are synthesized by plants, animals, and humans to be stored for food, structural support, or metabolized for energy.

 

Glycogen:

Glycogen is the storage form of glucose in animals and humans which is analogous to the starch in plants. Glycogen is synthesized and stored mainly in the liver and the muscles. Structurally, glycogen is very similar to amylopectin with alpha acetal linkages, however, it has even more branching and more glucose units are present than in amylopectin. Various samples of glycogen have been measured at 1,700-600,000 units of glucose.

The structure of glycogen consists of long polymer chains of glucose units connected by an alpha acetal linkage. The graphic on the left shows a very small portion of a glycogen chain. All of the monomer units are alpha-D-glucose, and all the alpha acetal links connect C # 1 of one glucose to C # 4 of the next glucose.

The branches are formed by linking C # 1 to a C # 6 through an acetal linkages. In glycogen, the branches occur at intervals of 8-10 glucose units, while in amylopectin the branches are separated by 12-20 glucose units.

Glycogen - Chime in new window

Acetal Functional Group:

Carbon # 1 is called the anomeric carbon and is the center of an acetal functional group. A carbon that has

two ether oxygens attached is an acetal.

The Alpha position is defined as the ether oxygen being on the opposite side of the ring as the C # 6. In the chair structure this results in a downward projection. This is the same definition as the -OH in a hemiacetal.

Open graphic of hemiacetal in a new window

Starch vs. Glycogen:

Plants make starch and cellulose through the photosynthesis processes. Animals and human in turn eat plant materials and products. Digestion is a process of hydrolysis where the starch is broken ultimately into the various monosaccharides. A major product is of course glucose which can be used immediately for metabolism to make energy. The glucose that is not used immediately is converted in the liver and muscles into glycogen for storage by the process of glycogenesis. Any glucose in excess of the needs for energy and storage as glycogen is converted to fat.

 Ribose

Ribose and its related compound, deoxyribose, are the building blocks of the backbone chains in nucleic acids, better known as DNA and RNA. Ribose is used in RNA and deoxyribose is used in DNA. The deoxy- designation refers to the lack of an alcohol, -OH, group as will be shown in detail further down.

Ribose and deoxyribose are classified as monosaccharides, aldoses, pentoses, and are reducing sugars.

Click for larger image 

Ring Structure for Ribose:

The chair form of ribose follows a similar pattern as that for glucose with one exception. Since ribose has an aldehyde functional group, the ring closure occurs at carbon # 1, which is the same as glucose. See the graphic on the left.

The exception is that ribose is a pentose, five carbons. Therefore a five membered ring is formed. The -OH on carbon #4 is converted into the ether linkage to close the ring with carbon #1. This makes a 5 member ring - four carbons and one oxygen. 

Steps in the ring closure (hemiacetal synthesis):1. The electrons on the alcohol oxygen are used to bond the carbon #1 to make an ether (red oxygen atom).2. The hydrogen (green) is transferred to the carbonyl oxygen (green) to make a new alcohol group (green).

The chair structures are always written with the orientation depicted on the left to avoid confusion.

Hemiacetal Functional Group:

Carbon # 1 is now called the anomeric carbon and is the center of a hemiacetal functional group. A carbon that has both an ether oxygen and an alcohol group is a hemiacetal.

Open graphic of hemiacetal in a new window

Click for larger image  

 

Compare Ribose and Deoxyribose Structures:

The presence or absence of the -OH group on carbon (#2) is an important distinction between ribose and deoxyribose. Ribose has an alcohol at carbon # 2, while deoxyribose does not have the alcohol group. See red -OH and H in the structures on the left.

The Beta position is defined as the -OH being on the same side of the ring as the C # 6. In the ring structure this results in a upward projection.

The Alpha position is defined as the -OH being on the opposite side of the ring as the C # 6. In the ring structure this results in a downward projection.

The alpha and beta label is not applied to any other carbon - only the anomeric carbon, in this case # 1.

Dextrose

Dextrose, commonly called glucose, d-glucose, or blood sugar, occurs naturally in food, and is moderately sweet. It is a monosaccharide (basic unit of carbohydrates, C6H1206) and has a high glycemic index (digested carbohydrates ability to raise blood glucose levels, also called Gl) ranking at 100.

Amylopectin is a polysaccharide with a varying structure; It is composed of linearly linked alpha 1,4 linked glucose units (coiled into tubular sections) with occasional alpha 1-6 glycosidic bonds which provide branching points. Each amylopectin molecule may contain 100,000-200,000 glucose units, and each branch is about 20 or 30 glucose units in length, so that these molecules are bushy and nearly spherical in shape. 

The many exposed ends can have more glucose units added to them by enzyme action for storage 

purposes or removed from them for use in respiration. 

Amylopectin is one fraction of starch (typicaly 80-90%), the other fraction being amylose (10-20%). Glycogen ("animal starch"), found in the liver and muscles, is effectively similar in structure to amylopectin, but it has shorter branches: 8-12 glucose units. 

This simple model - specifically prepared for this website by the Sweet program - shows 84 glucose units. The 1-4 linked sections can be seen to coil into a helical shape, and the 1-6 linkage forms a helical branch away from the main section.

Starch

Starch is the major form of stored carbohydrate in plants.   Starch   is   composed   of   a   mixture   of   two substances: amylose,   an   essentially   linear polysaccharide, and amylopectin,  a highly branched 

polysaccharide.  Both   forms of  starch are  polymers of α-D-Glucose.   Natural   starches   contain   10-20% amylose and 80-90% amylopectin. Amylose forms a colloidal   dispersion   in   hot  water   (which   helps   to thicken gravies) whereas amylopectin is completely insoluble.

Amylose molecules consist typically of 200 to 20,000 glucose units  which form a helix as a result of the bond angles between the glucose units. 

Amylose

Amylopectin differs from amylose in being highly branched. Short side chains of about   30   glucose  units   are   attached  with 1α→6 linkages approximately every twenty to   thirty   glucose   units   along   the   chain. Amylopectin molecules  may contain  up to two million glucose units.

Amylopectin

The side branching chains are clustered together within the amylopectin molecule

Starches   are   transformed   into   many   commercial products   by   hydrolysis   using   acids   or   enzymes   as catalysts. Hydrolysis is a chemical reaction in which water   is  used   to  break   long  polysaccharide  chains into smaller chains or into simple carbohydrates. The resulting   products   are   assigned   a   Dextrose 

Equivalent (DE) value which is related to the degree of   hydrolysis.   A   DE   value   of   100   corresponds   to completely hydrolyzed starch, which is pure glucose (dextrose). Dextrinsare   a   group   of   low-molecular-weight carbohydrates produced by the hydrolysis of starch.   Dextrins   are   mixtures   of   polymers   of   D-glucose  units   linked  by  1α→4 or   1α→6 glycosidic bonds. Maltodextrin is   partially   hydrolyzed   starch that   is   not   sweet   and   has   a   DE   value   less than 20. Syrups, such as corn syrup made from corn starch, have DE values from 20 to 91.   Commercial dextrose has DE values   from 92 to 99. Corn syrup solids,   which   may   be   labeled   as soluble corn fiber or resistant maltodextrin,   are   mildly   sweet semi-crystalline   or   powdery   amorphous   products with DEs from 20 to 36 made by drying corn syrup in a vacuum or in spray driers. Resistant maltodextrin or   soluble   corn  fiber  are  not  broken  down  in   the digestive system, but they are partially fermented by colonic  bacteria   thus providing only  2 Calories  per gram   instead   of   the   4   Calories   per   gram   in   corn syrup. High Fructose Corn Syrup (HFCS), commonly used to sweeten soft drinks, is made by treating corn syrup   with   enzymes   to   convert   a   portion   of   the glucose   into   fructose.   Commercial   HFCS   contains from   42%   to   55%   fructose,   with   the   remaining percentage being mainly glucose. There is an effort underway   to   rename   High   Fructose   Corn   Syrup as Corn Sugar because   of   the   negative   public perception   that   HFCS   contributes   to obesity. Modified starch is   starch   that   has   been changed   by   mechanical   processes   or   chemical treatments   to   stabilize   starch   gels  made  with  hot water.   Without   modification,   gelled   starch-water mixtures   lose  viscosity  or  become  rubbery  after  a few   hours. Hydrogenated glucose syrup (HGS)   is produced   by   hydrolyzing   starch,   and   then hydrogenating the resulting syrup to produce sugar alcohols   like   maltitol   and   sorbitol,   along   with hydrogenated   oligo-   and polysaccharides. Polydextrose (poly-D-glucose)   is   a synthetic, highly-branched polymer with many types of   glycosidic   linkages   created  by  heating  dextrose with   an   acid   catalyst   and   purifying   the   resulting water-soluble   polymer.   Polydextrose   is   used   as   a bulking agent because it is tasteless and is similar to fiber   in   terms   of   its   resistance   to   digestion.   The name resistant starch is   applied   to   dietary   starch that   is   not   degraded   in   the   stomach   and   small intestine, but is fermented by microflora in the large intestine.

Relative sweetness of various carbohydrates

fructose 173invert sugar* 120HFCS (42% fructose) 120sucrose 100xylitol 100tagatose 92glucose 74high-DE corn syrup 70sorbitol 55

mannitol 50trehalose 45regular corn syrup 40galactose 32maltose 32lactose 15

Amylose is a linear polymer made up of D-glucose units.

This polysaccharide is one of the two components 

of starch, making up approximately 20-30% of the 

structure. The other component is amylopectin, 

which makes up 70-80% of the structure.[1]

Because of its tightly packed structure, amylose is 

more resistant to digestion than other starch 

molecules and is therefore an important form 

of resistant starch, which has been found to be an 

effective prebiotic.[2]

[edit]Structure

Amylose is made up of α(1→4) bound glucose 

molecules. The carbon atoms on glucose are 

numbered, starting at the aldehyde (C=O) carbon, 

so, in amylose, the 1-carbon on one glucose 

molecule is linked to the 4-carbon on the next 

glucose molecule (α(1→4) bonds).[3] The structural 

formula of amylose is pictured at right. The number 

of repeated glucose subunits (n) is usually in the 

range of 300 to 3000, but can be many thousands.

There are three main forms of amylose chains can 

take. It can exist in a disordered amorphous 

conformation or two different helical forms. It can 

bind with itself in a double helix(A or B form), or it 

can bind with another hydrophobic guest molecule 

such as iodine, a fatty acid, or an aromatic 

compound. This is known as the V form and is 

how amylopectin binds to amylose to form starch. 

Within this group, there are many different 

variations. Each is notated with V and then a 

subscript indicating the number of glucose units per 

turn. The most common is the V6 form, which has six 

glucose units a turn. V8 and possibly V7 forms exist 

as well. These provide an even larger space for the 

guest molecule to bind.[4]

This linear structure can have some rotation around 

the phi and psi angles, but, for the most part, bound 

glucose ring oxygens lie on one side of the structure. 

The α(1→4) structure promotes the formation of 

a helix structure, making it possible for hydrogen 

bonds form between the oxygen atoms bound at 2-

carbon of one glucose molecule and the 3-carbon of 

the next glucose molecule.[5]

[edit]Physical properties

Unlike amylopectin, amylose is insoluble in water.[6] It also reduces the crystallinity of amylopectin and 

how easily water can infiltrate the starch.[7] The 

higher the amylose content, the less expansion 

potential and the lower the gel strength for the same 

starch concentration. This can be countered partially 

by increasing the granule size.[8]

Fiber X-ray diffraction analysis coupled with 

computer-based structure refinement has found A-, 

B-, and C- polymorphs of amylose. Each form 

corresponds to either the A-, the B-, or the C- starch 

forms. A- and B- structures have different helical 

crystal structures and water contents, whereas the 

C- structure is a mixture of A- and B- unit cells, 

resulting in an intermediate packing density 

between the two forms.[9]

[edit]Function

Amylose is important in plant energy storage. It is 

less readily digested than amylopectin; however, 

because it is more linear than amylopectin, it takes 

up less space. As a result, it is the preferred starch 

for storage in plants. It makes up about 30% of the 

stored starch in plants, though the specific 

percentage varies by species. The digestive enzyme 

α-amylase is responsible for the breakdown of the 

starch molecule into maltotriose and maltose, which 

can be used as sources of energy.

Amylose is also an important thickener, water 

binder, emulsion stabilizer, and gelling agent in both 

industrial and food-based contexts. Loose helical 

amylose chains have a hydrophobic interior that can 

bind to hydrophobic molecules such 

as lipids and aromatic compounds. The one problem 

with this is that, when it crystallizes or associates, it 

can lose some stability, often releasing water in the 

process (syneresis). When amylose concentration is 

increased, gel stickiness decreases but gel firmness 

increases. When other things 

including amylopectin bind to amylose, 

the viscosity can be affected, but incorporating κ-

carrageenan, alginate, xanthan gum, or low-

molecular-weight sugars can reduce the loss in 

stability. The ability to bind water can add substance 

to food, possibly serving as a fat replacement.[10] For 

example, amylose is responsible for causing white 

sauce to thicken, but, upon cooling, some separation 

between the solid and the water will occur.

In a laboratory setting, it can act as a 

marker. Iodine molecules fit neatly inside the helical 

structure of amylose, binding with the starch 

polymer that absorbs certain known wavelengths of 

light. Hence, a common test is the iodine test for 

starch. Mix starch with a small amount of yellow 

iodine solution. In the presence of amylose, a blue-

black color will be observed. The intensity of the 

color can be tested with a colorimeter, using a red 

filter to discern the concentration of starch present 

in the solution. It is also possible to use starch as an 

indicator in titrations involving iodine reduction.[11] It 

is also used in amylose magnetic beads and resin to 

separate maltose-binding protein   [12]   

[edit]Recent studies

High-amylose varieties of rice, the less sticky long-

grain rice, have a much lower glycemic load, which 

could be beneficial for diabetics.

Researchers have identified the gene granular 

binding starch synthase, or GBSS, in potatoes. It is 

responsible for encoding for the enzyme that directs 

amylase starch production. If it is inhibited, amylose 

production will also be interrupted.[13

What is Amylose?Amylose is a group of carbohydrate chains that includes dextrin and cellulose. The term carbohydrate simply means carbon, hydrogen and oxygen and refers to whole grains, legumes, fruits and vegetables. Dextrin aids in the breakdown of starch during digestion. Cellulose is the fibrous form of the molecule that aids in the transport of starch during digestion. The amylose molecule provides a high fiber source with a low glycemic index. The more amylose present, the lower the glycemic index. Diabetics may benefit from a diet high in amylose because of the slower insulin response, which prevents quick spikes in glucose levels. Research is being conducted on the benefits of a high amylose diet

in the prevention of colon cancer and heart disease.Whole GrainsWhole-grain foods have a significant amount of amylose and include wheat, wild rice, rye, barley, oats, bulgur, corn, millet, quinoa, amaranth, barley, buckwheat, sorghum and triticale, a hybrid between wheat and rye. The U.S. Food and Drug Administration recommends that food products labeled "whole grain" should include an intact grain that has not had the endosperm, germ or bran removed. Breads, cereals and certain pastas labeled "whole grain" may have a higher amylose content than foods simply labeled "wheat," such as in wheat bread. Regular white rice and pastas are not high in amylose and do not have a low glycemic index.LegumesLegumes refer to dried beans, lentils and peas and are an abundant source of amylose. Black-eyed peas, lentils, black, garbanzo, chili, great northern and kidney beans are some of the many dried beans and peas available. Dried legumes can be soaked and boiled for use on salads or in soups. Some beans can be mashed and used as spreads and dips such as hummus.Other Foods

Bananas have a high amylose content. Certain root vegetables are also high in amylose, such as sweet potatoes, radishes and parsnips. White potatoes do not have many of the complex chains of the amylose molecule and are not considered a low glycemic index food. Amylose or resistant starch in powder form is available to help boost fiber in smoothies and baked goods.

Galactomannan

Galactomannans are polysaccharides consisting of a mannose backbone with galactose side groups. The mannopyranose units are linked with 1β→4 linkages to  which   galactopyranose  units   are   attached  with 1α→6   linkages.   Galactomannans   are   present   in several vegetable gums that are used to increase the viscosity   of   food   products.   These   are   the approximate ratios of mannose to galactose for the following gums:

Fenugreek gum, mannose:galactose 1:1 Guar gum, mannose:galactose 2:1 Tara gum, mannose:galactose 3:1 Locust   bean   gum or Carob   gum, 

mannose:galactose 4:1

Guar   is   a   legume   that   has   been   traditionally cultivated as livestock feed. Guar gum is also known by   the  namecyamopsis tetragonoloba which   is   the Latin   taxonomy   for   the   guar   bean   or   cluster bean. Guar   gum is   the   ground   endosperm   of   the seeds. Approximately 85% of guar gum is guaran, a water   soluble   polysaccharide   consisting   of   linear chains   of  mannose  with   1β→4   linkages   to  which galactose   units   are   attached  with   1α→6   linkages. The ratio of mannose to galactose is 2:1. Guar gum has five to eight times the thickening power of starch and has many uses in the pharmaceutical industry, as a food stabilizer, and as a source of dietary fiber.

Guaran is the principal polysaccharide in guar gum. 

Arabinoxylan

Arabinoxylans are polysaccharides found in the bran of grasses and grains such as wheat, rye, and barley. Arabinoxylans  consist  of  a  xylan  backbone  with  L-arabinofuranose   (L-arabinose   in   its   5-atom   ring form)   attached   randomly   by   1α→2   and/or   1α→3 

linkages   to   the  xylose  units   throughout   the  chain. Since   xylose   and   arabinose   are   both   pentoses, arabinoxylans   are   usually   classified   as   pentosans. Arabinoxylans are important in the baking industry. The arabinose units bind water and produce viscous compounds that affect the consistency of dough, the retention   of   gas   bubbles   from   fermentation   in gluten-starch  films,  and  the  final   texture  of  baked products.

Arabinoxylan

Chitin

Chitin   is   an   unbranched   polymer   of   N-Acetyl-D-glucosamine. It is found in fungi and is the principal component   of   arthropod   and   lower   animal exoskeletons, e.g., insect, crab, and shrimp shells. It may   be   regarded   as   a   derivative   of   cellulose,   in which the hydroxyl groups of the second carbon of each   glucose   unit   have   been   replaced   with acetamido (-NH(C=O)CH3) groups.

Chitin

Fucoidan is a sulfated polysaccharide (MW: 

average 20,000) found mainly in various species 

of brown algae and brown seaweed such 

as mozuku, kombu, limu moui, bladderwrack, wakam

e, and hijiki (variant forms of fucoidan have also been 

found in animal species, including the sea cucumber). 

Fucoidan is used as an ingredient in some dietary 

supplement products.

[edit]Research

There at least two distinct forms of fucoidan: F-

fucoidan, which is >95% composed of 

sulfated esters of fucose, and U-fucoidan, which is 

approximately 20% glucuronic acid.

The physiological and biochemical effects of fucoidan 

have been examined in several small-scale in 

vitro and animal studies. F-fucoidan was reported to 

inhibit hyperplasia in rabbits [1] and 

induce apoptosis in isolated human lymphoma cell 

lines in vitro.[2]. It has been hypothesized that these 

two effects may involve a common mechanism, but 

the evidence is inconsistent and no mechanism for 

the putative induction of apoptosis by fucoidan has 

been identified.[3] A study in rats indicated that pre-

treatment with fucoidan increases mortality 

subsequent to meningitis infection.[4] In a clinical 

study, orally-ingested Undaria-derived-fucoidan was 

reported to produce a small increase in the total 

number of CD34+ cells, and a more pronounced 

increase in the proportion of CD34+ cells that 

expressedCXCR4. The authors of the study 

hypothesized that the ability of fucoidan to mobilize 

hematopoetic cells with high levels of CXCR4 

expression could be clinically valuable.[5]

Mannan is a plant polysaccharide that is 

a polymer of the sugar mannose.[1]

Detection of mannan leads to lysis in the mannan-

binding lectin pathway.It is generally found in yeast, 

bacteria and plants. Plant mannans have β(1-4) 

linkages. It is a form of storage polysaccharide. Ivory 

nut is composed of mannan.

Xylan (CAS number:9014-63-5) is a generic term used to describe a wide variety of highly 

complex polysaccharides that are found in plant cell 

walls and some algae. Xylans are polysaccharides 

made from units of xylose (a pentose sugar).

Xylan is found in the cell walls of some green algae, 

especially macrophytic siphonous   genera   , where it 

replaces cellulose. Similarly, it replaces the inner 

fibrillar cell-wall layer of cellulose in some red algae.

Xylan is one of the foremost anti-nutritional factors in 

common use feedstuff raw materials. Laminarin is a polysaccharide carbohydrate very much like starch, 

except it functions as an energy storage compound 

for Laminaria and other brown algae like kelp. These 

are large seaweeds of about thirty different genera. It 

grows in underwater kelp forests in clear shallow salt 

water and requires reasonably warm nutrient rich 

water.

Laminarin is clearly a high-energy carbohydrate. It is directly produced 

by photosynthesis in an algae that grows in long 

stalks at the rate of as much as 30 centimeters per 

day, up to 60 meters total. Laminarin is the nutrient-

rich part of kelp that feeds hundreds of sea animals. 

In addition, kelp is an important part of the Japanese 

diet and the diets of several other sea-dependent 

cultures.

Though we don't yet know much about laminarin, it 

has some very useful properties. It is rich in iodines 

and alkali, as well as calcium. Ash produced by kelp is 

used in soap and glass production, and laminarin can 

be used as a thickener in several industries, like ice 

cream, jelly, and toothpaste. Bladderwort is one form 

of kelp that is used in several health-food products to 

promote a healthy urinary tract, and it's probable 

that the laminarin is part of what produces its 

purported effects.

Chrysolaminarin is a linear polymer of β(1→3) and β(1→6) linked glucose units in a ratio of 

11:1.[1][2] It used to be known as leucosin. 

Chrysolaminarin is arguably one of the most common 

biopolymers in the world with cellulose being the 

other.

[edit]Function

Chrysolaminarin is a storage polysaccharide typically 

found in photosynthetic heterokonts. It is used as a 

carbohydrate food reserve by phytoplankton such 

as Bacillariophyta (similar to the use 

of laminarin by brown algae).[3]

Chrysolaminarin is stored inside the cells of these 

organisms dissolved in water and encapsuled 

in vacuoles whose refractive index increases with 

chrysolaminarin content. In 

addition, heterokont algae use oil as a storage 

compound. Besides energy reserve, oil helps the 

algae to control their buoyancy.[4]

Common Carbohydrates Name  Derivation of name and Source

Monosaccharides

 GlucoseFrom Greek word for sweet wine; grape sugar, blood sugar, dextrose.

 GalactoseGreek word for milk--"galact", found as a component of lactose in milk.

 Fructose

Latin word for fruit--"fructus", also known as levulose,found in fruits and honey; sweetest sugar.

 RiboseRibose and Deoxyribose are found in the backbone structure of RNA and DNA, respectively.

Disaccharides - contain two monosaccharides

  Sucrose

French word for sugar--"sucre", a disaccharide containingglucose and fructose; table sugar, cane sugar, beet sugar.

 LactoseLatin word for milk--"lact"; a disaccharide found in milk containing glucose and galactose.

 Maltose

French word for "malt"; a disaccharide containing two units of glucose; found in germinating grains, used to make beer.

Common Polysaccharides

 Carbohydrate - MiniTopics

MiniTopics:

Glucose - Blood Sugar Chemical Test

Galactose - Galactosemia - Genetic Enzyme Deficiency

Maltose - Beer and Malted Barley

Lactose - Lactose Intolerance

Sucrose - Sugar and Tooth Decay

Starch - Corn Syrup and High Fructose Corn Syrup

Starch - Starch-Iodine Test

Sweetness - Sweeteners   , Sweetness Scale, Sweet Receptor Site

Cellulose - Fiber in the Diet

 Name  Source

 Starch

Plants store glucose as the polysaccharide starch. The cereal grains (wheat, rice, corn, oats, barley) as well as tubers such as potatoes are rich in starch.

Cellulose

The major component in the rigid cell walls in plants is cellulose and is a linear polysaccharide polymer with many glucose monosaccharide units.

 Glycogen

This is the storage form of glucose in animals and humans which is analogous to the starch in plants. Glycogen is synthesized and stored mainly in the liver and the muscles.

 

Click for larger image

 Carbohydrates - IntroductionIntroduction:

General names for carbohydrates include sugars, starches, saccharides, and polysaccharides. The term saccharide is derived from the Latin word " sacchararum" from the sweet taste of sugars.

The name "carbohydrate" means a "hydrate of carbon." The name derives from the general formula of carbohydrate is Cx(H2O)y - x and y may or may not be equal and range in value from 3 to 12 or more. For example glucose is: C6(H2O)6 or is more commonly written, C6H12O6.

The chemistry of carbohydrates most closely resembles that of alcohol, aldehyde, and ketone functional groups. As a result, the modern definition of a CARBOHYDRATE is that the compounds are polyhydroxy aldehydes or ketones. The chemistry of carbohydrates is complicated by the fact that there is a functional group (alcohol) on almost every carbon. In addition, the carbohydrate may exist in either a straight chain or a ring structure. Ring structures incorporate two additional functional groups: the hemiacetal and acetal.

A major part of the carbon cycle occurs as carbon dioxide is converted to carbohydrates through photosynthesis. Carbohydrates are utilized by animals and humans in metabolism to

produce energy and other compounds.

Click for larger imageCarbohydrate Functions:

Carbohydrates are initially synthesized in plants from a complex series of reactions involving photosynthesis.

-Store energy in the form of starch (photosynthesis in plants) or glycogen (in animals and humans).

-Provide energy through metabolism pathways and cycles.

-Supply carbon for synthesis of other compounds.

-Form structural components in cells and tissues.

Photosynthesis is a complex series of reactions carried out by algae, phytoplankton, and the leaves in plants, which utilize the energy from the sun. The simplified version of this chemical reaction is to utilize carbon dioxide molecules from the air and water molecules and the energy from the sun to produce a simple sugar such as glucose and oxygen molecules as a by product. The simple sugars are then converted into other molecules such as starch, fats, proteins, enzymes, and DNA/RNA i.e. all of the other molecules in living plants. All of the "matter/stuff" of a plant ultimately is produced as a result of this photosynthesis reaction.

Click for larger image

Metabolism: 

Metabolism occurs in animals and humans after the ingestion of organic plant or animal foods. In the cells a series of complex reactions occurs with oxygen to convert for example glucose sugar into the products of carbon dioxide and water and ENERGY. This reaction is also carried out by bacteria in the decomposition/decay of waste materials on land and in the water. Combustion occurs when any organic material is reacted (burned) in the presence of oxygen to give off the products of carbon dioxide and water and ENERGY. The organic material can be any fossil fuel such as natural gas (methane), oil, or coal. Other organic materials that combust are wood, paper, plastics, and cloth. The whole purpose of both processes is to convert chemical energy into other forms of energy such as heat.

 Di-, Poly-Carbohydrates - IntroductionIntroduction:

General names for carbohydrates include sugars, starches, saccharides, and polysaccharides. The term saccharide is derived from the Latin word " sacchararum" from the sweet taste of sugars.

Monosaccharides contain one sugar unit such as glucose, galactose, fructose, etc.

Disaccharides contain two sugar units. In almost all cases one of the sugars is glucose, with the other sugar being galactose, fructose, or another glucose. Common disaccharides are maltose, lactose, and sucrose.

Polysaccharides contain many sugar units in long polymer chains of many repeating units. The most common sugar unit is glucose. Common poly saccharides are starch, glycogen, and cellulos

Disaccharide descriptions and componentsDisaccharide Description Component monosaccharides

sucrose common table sugar glucose 1α→2 fructose

maltose product of starch hydrolysis glucose 1α→4 glucose

trehalose found in fungi glucose 1α→1 glucose

lactose main sugar in milk galactose 1β→4 glucose

melibiose found in legumes galactose 1α→6 glucose