PRIMARY METABOLITES

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PRIMARY METABOLITES

• Sirintorn Pisutthanan
• 9 November 2006

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• ??????????? ???????????????????????????
• ?????????????????? ??????????????????
  ??????????????????
• ?????????????????????????????????????? ??????????
  (Organic compound)
• ?????????? ???? ????????????????
  ?????????????????? ?????????????? ?????????????
  ???? ???????????????

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????????????? Biological molecules

• 4 major classes of small biological molecules
  found in cells
• sugars
• fatty acids
• amino acids
• nucleotides

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Carbohydrates

• ??? ????????????????????????????????? ????????
  ???????????
• ????????????????????????????????????????
• ??????????????????????????????????????????,
  OH, ?????????????, -CHO ????????????, CO

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• Common monosaccharides in cells have 4, 5, or
  6 carbon atoms
• Common 5 and 6 carbons sugars usually exist as 5-
  or 6-membered ring structures in cells, with one
  oxygen atom in the ring.

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• Monosaccharides forming a five-sided ring, like
  ribose, are called furanoses.
• Those forming six-sided rings, like glucose, are
  called pyranoses.

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??????? carbohydrates

• 1. The basic form of carbohydrates are simple
  sugars or monosaccharides.
• ????????????? ??????????? ????????
• These simple sugars can combine with each other
  to form more complex carbohydrates.

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• Glucose, also called dextrose, is the most widely
  distributed sugar in the plant and animal
  kingdoms and it is the sugar present in blood as
  "blood sugar".

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• Fructose, also called levulose or "fruit sugar",
  is shown here in the chain and ring forms.
• Fructose and glucose are the main carbohydrate
  constituents of honey.

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• Many simple sugars can exist in a chain form or a
  ring form. The ring form is favored in aqueous
  solutions.

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• The mechanism of ring formation is similar for
  most sugars.
• The glucose ring form is created when the oxygen
  on carbon number 5 links with the carbon
  comprising the carbonyl group (carbon number 1)
  and transfers its hydrogen to the carbonyl oxygen
  to create a hydroxyl group.

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• 2. Carbohydrates consisting of two to ten simple
  sugars are called oligosaccharides or compound
  sugar

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• The combination of two simple sugars is a
  disaccharide.
• (two carbohydrates
• linked together
• ie. sucrose)

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Sucrose common table sugar glucose fructose
Lactose main sugar in milk galactose glucose
Maltose product of starch hydrolysis
glucose glucose
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trisaccharides

• Raffinose, melitose, found in beans, cabbage,
  brussels sprouts, and broccoli.
• Humans cannot digest this saccharide and it is
  fermented in the large intestine by gas-producing
  bacteria.

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trisaccharides Raffinose, melitose galactose
connected to sucrose via a 1a?6 glycosidic linkage
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• 3. and those with a larger number (more than 11
  simple sugars) are called polysaccharides.

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• Starch and Cellulose
• only differ in how the carbohydrates are linked
  together.
• Starch chain of a-glucose subunits

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Cellulose chain of b-glucose subunits
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starch and glycogen are polymers of alpha
glucose.
C1
C1
C1
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starch
C1
C1
C1
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Amylose, a form of starch, have alpha 1-4
glycosidic bonds
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Amylopectin, a form of starch and
glycogen have alpha 1-4 and alpha 1-6
glycosidic bonds.
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Starch hydrolysis

• Starches are transformed into many commercial
  products by hydrolysis.
• Dextrose Equivalent (DE) value which is related
  to the degree of hydrolysis.
• DE value of 100 corresponds to completely
  hydrolyzed starch, which is pure glucose
  (dextrose).

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• 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.
• 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.

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Relative sweetness of various carbohydrates

• fructose 173 invert sugar 120
• HFCS (42 fructose) 120 sucrose 100
• xylitol 100 glucose
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• high-DE corn syrup 70 sorbitol 55
• mannitol 50 regular corn syrup 40
• Galactose, maltose 32 lactose 15
  
• invert sugar is a mixture of glucose and
  fructose found in fruits.

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glycogen
have alpha 1-4 and alpha 1-6 glycosidic bonds.
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Cellulose

• a polymer of ß-D-Glucose, is oriented with -CH2OH
  groups alternating above and below the plane of
  the cellulose molecule thus producing long,
  unbranched chains.

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• Partially nitrated cellulose, known as pyroxylin,
  is used in the manufacture of collodion,
  plastics, lacquers, and nail polish.

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Chitin

• an unbranched polymer of N-Acetyl-D-glucosamine.
• a derivative of cellulose, in which the hydroxyl
  groups of the second carbon of each glucose unit
  have been replaced with acetamido
  (-NH(CO)CH3) groups.

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chitin is a polymer of N-acetyl
glucosamine the cuticular exoseleten of
arthropods
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Inulin polymers consisting of fructose units that
typically have a terminal glucose
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Sugar Alcohols

• are the hydrogenated forms of the aldoses or
  ketoses. For example,
• glucitol, also known as sorbitol, has the same
  linear structure as the chain form
• of glucose, but the aldehyde
• group is replaced with
• a -CH2OH group.

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• Other common sugar alcohols include the
  monosaccharides erythritol and xylitol
• Sugar alcohols have about half the calories of
  sugars and are frequently used in low-calorie or
  "sugar-free" products.

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• Xylitol, which has the hydroxyl groups oriented
  like xylose, is a very common ingredient in
  "sugar-free" candies and gums because it is
  approximately as sweet as sucrose, but contains
  40 less food energy.

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Amino sugars

• or aminosaccharides replace
• a hydroxyl group with
• an amino (-NH2) group.
• Glucosamine is an amino sugar used to treat
  cartilage damage and reduce the pain and
  progression of arthritis.

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Uronic acids

• have a carboxyl group (-COOH) on the carbon that
  is not part of the ring.
• Their names retain the root of
• the monosaccharides, For example,
• the structure of glucuronic acid corresponds to
  glucose.

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• Many saccharide structures differ only in the
  orientation of the hydroxyl groups (-OH).
• This slight structural difference makes a big
  difference in
• the biochemical properties,
• organoleptic properties (e.g., taste), and
• in the physical properties such as melting point
  and Specific Rotation.

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Aldose Ketose

• A chain-form monosaccharide that has a carbonyl
  group (CO) on an end carbon forming an aldehyde
  group (-CHO) is classified as an aldose.
• When the carbonyl group is on an inner atom
  forming a ketone, it is classified as a ketose.

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• in the acyclic form, The critical centers are
  marked in the diagrams with .

D-glucose an aldose an aldohexose
D-fructose a ketose  a ketohexose
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• The anomeric center is important to the
  reactivity of carbohydrates because it is the
  site at which ring opening occurs, becoming the
  carbonyl group, the important functional group.

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• The anomeric carbon or the anomeric center
• can be recognised by looking for the C that
• is attached to two O atoms by single bonds.

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• In the cyclic form, find the anomeric center ()
  and look at the substituents. If one is an H, it
  is an aldose.

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Epimers

• Structures that have opposite configurations of a
  hydroxyl group at only one position, such as
  glucose and mannose.

mannose
glucose
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Anomers

• The rearrangement produces
• alpha glucose when the hydroxyl group (-OH) is on
  the opposite side of the methyl (-CH2OH)
  group, or
• beta glucose when the -OH group is on the same
  side as the -CH2OH group.

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a-D-glucose, b-D-glucose
the beta (b) form -OH group from the 1st carbon
atom going up
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the alpha (a) form, -OH points down
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enantiomers

• Compounds that are mirror images of each other
  but are not identical, comparable to left and
  right shoes.
• Different configurations have different chemical
  and biological properties.

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D-form, L-form

• Carbohydrates are defined as either D- or L- by
  comparing the stereochemistry at the chirality
  center next to the CH2OH group.

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• at the chirality center next to CH2OH
• L-glyceraldehyde has the -OH group on the left
• and D-glyceraldehyde the hydroxyl group on the
  right

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• Key - D-form, L-form ??????????
• Chiral carbon ????????????? CH2OH group