Download Monosaccharides Technical Information

Technical Information - Carbohydrates 1
Monosaccharides
Hexose sugars (containing 6 carbon atoms)
CH2OH
COOH
O
H
Pentose sugars (containing 5 carbon atoms)
H
OH
H
H
OH
H
H
HO
OH
OH
H
OH
H
H
H
HO
HO
H
OH
H
H
OH
OH
H
OH
Glucuronic acid
Glucose
H
H
H
OH
H
O
OH
H
HO
H
O
HOCH2
O
Arabinose
Xylose
Disaccharides
Cellobiose
Galacturonic acid residue
CH2OH
O
H
H
O
O
O
O
H
COOH
COOH
CH2OH
H
OH
H
O
HO
OH
H
H
OH
H
H
Glucose
OH
H
H
OH
Glucose
H
O
H
OH
H
OH
H
H
OH
Glucuronic acid
Isomaltose
CH2OH
CH2OH
CH2OH
O
H
OH
Glucuronic acid
Maltose
H
O
H
H
H
H
O
O
H
H
H
H
OH
H
H
CH2
HO
OH
H
O
OH
H
HO
H
OH
H
O
O
H
H
H
OH
Glucose
H
OH
Glucose
H
H
OH
Glucose
HO
OH
H
H
OH
OH
Glucose
Trisaccharides
Isomaltotriose
CH2OH
O
H
H
H
CH2
HO
OH
H
O
O
H
H
H
H
CH2
OH
Glucose
HO
OH
H
O
O
H
H
H
H
OH
Glucose
HO
OH
H
H
OH
OH
Glucose
Berkshire Functional Foods, Special Foods Division, The University of Reading, UK
Carbohydrates 1
Technical Information - Carbohydrates 2
Polysaccharides
Starch
Naturally ocurring starch is a polymer of glucose arranged in one of two ways:
Amylose
an unbranched chain of glucose units usually 200-20,000 units long.
Amylopectin
a branched form of amylose (shown below). Short chains of about 30 glucose units
are attached to the amylose molecule every 20-30 units along the chain.
Some enzymes are capable of breaking the bonds forming the branches (α1-6 bonds) while
some enzymes break the bonds connecting glucose units within the amylose chain (α1-4 bonds).
CH2OH
CH2OH
CH2OH
O
H
H
H
OH
H
H
OH
O
O
H
H
O
H
H
H
O
OH
H
H
OH
H
OH
H
H
OH
O
α1-6 bond
α1-4 bond
CH2OH
H
O
CH2
CH2OH
O
CH2OH
O
O
H
H
H
O
OH
H
H
OH
H
H
H
H
O
OH
H
H
OH
CH2OH
O
H
H
O
OH
H
H
OH
O
H
H
OH
H
H
OH
H
H
O
H
O
OH
H
H
OH
Starch - repeating glucose units
Pectin
Pectin is a mixed group of polysaccharides. Each polysaccharide consists mainly of galacturonic acid
units. The -COOH group in a variable number of the units is altered (to a methyl ester) to form the
pectin molecule.
COOCH3
COOCH 3
COOH
H
H
H
O
OH
H
H
OH
O
H
H
O
H
OH
H
H
OH
O
H
H
O
H
COOCH3
COOCH 3
O
O
O
H
H
O
H
OH
H
H
OH
H
O
H
OH
H
H
OH
O
H
OH
H
H
OH
Pectin - repeating galacturonic acid units
Dextrins
Dextrins are polysaccharides formed by the incomplete breakdown of amylose and amylopectin of
starch. The resulting dextrin may or may not be branched, depending on the site of cleavage.
CH2OH
CH2OH
O
O
H
HO
H
H
OH
H
H
OH
O
O
HO
H
H
OH
H
H
OH
H
H
H
H
OH
O
H
H
OH
H
H
OH
CH2OH
O
O
H
OH
O
CH2
CH2OH
CH2OH
H
H
H
O
H
O
H
OH
H
H
OH
H
O
H
H
OH
H
H
OH
OH
Dextrins - repeating glucose units of varing length and branching
Berkshire Functional Foods, Special Foods Division, The University of Reading, UK
Carbohydrates 2
Technical Information - Carbohydrates 3
Dextran
Dextran is a polymer of the monosaccharide dextrose,
an optical isomer of glucose. It is a largely linear molecule,
although there is a limited degree of branching.
CH2
O
H
H
H
CH2
HO
OH
H
O
O
H
H
H
H
OH
HO
OH
H
H
OH
O
CH2
O
H
H
H
CH2
HO
OH
H
O
O
H
H
H
H
Dextran - repeating glucose (dextrose) units
CH2
OH
H
HO
O
O
H
H
H
H
CH2
OH
HO
OH
H
O
O
H
H
H
H
OH
HO
OH
H
H
OH
O
Xylans
HO
H
Xylans are a mixed group of polysaccharides.
Each molecule consists of xylose units with
branching of arabinose units.
OH
H
HOCH2
H
H
OH
H
O
H
O
H
OH
O
H
H
OH
H
H
H
H
OH
H
H
O
H
O
H
O
H
OH
H
H
OH
H
H
H
O
H
O
H
O
O
O
H
OH
H
H
O
O
H
H
OH
H
O
H
H
OH
H
Xylans - repeating xylose units with branching of arabinose side chains
Arabinans
Arabinans are a mixed group of polysaccharides. Each molecule consists mainly of arabinose units
which can be branched to varing degrees in one of two positions from the arabinose unit.
O
CH 2
H
H
H
HO
H
OH
O
CH 2
H
O
H
OH
H
H
CH 2
O
H
O
H
OH
HO
H
CH 2
O
H
H
O
H
OH
HO
H
CH 2
O
H
O
H
H
HO
O
H
H
O
Arabinans - repeating arabinose units of varing length and branching
OH
H
CH 2
Berkshire Functional Foods, Special Foods Division, The University of Reading, UK
H
H
HO
O
O
H
Carbohydrates 3
Technical Information - Carbohydrates 4
Cellulose
Cellulose is a polymer of glucose but unlike starch, it is not branched. Also, the -CH2OH groups of
the glucose units alternate above and below the plane of the molecule. The lack of branching allows
the long chains to lie close together to form rigid structures.
CH2OH
H
CH2OH
OH
H
O
H
OH
H
OH
OH
H
OH
O
H
H
H
H
H
O
H
O
H
H
O
OH
H
H
H
OH
H
H
O
H
H
O
OH
H
H
OH
H
O
O
H
CH2OH
O
O
H
CH2OH
OH
CH2OH
Cellulose - repeating glucose units
Hemicellulose
Hemicellulose is a polysaccharide made up of many different monosaccharide units. In contrast to
cellulose, hemicellulose has a random structure with little strength.
Monosaccharides that make up hemicellulose include:
Hexose sugars:
Pentose sugars:
glucose, galactose, mannose
arabinose and xylose
Of these, xylose is present in the largest amount.
β-Glucans
β-glucans consist of repeating glucose units, up to 250,000 units long. Like cellulose, the molecule
is not branched. Unlike cellulose, however, where bonding of each glucose unit occurs at the same
position, every three to four units the next glucose is attached at a different position.
H
OH
HO
O
H
H
H
CH2OH
O
CH2OH
H
OH
H
OH
H
O
OH
O
H
H
H
H
H
O
H
CH2OH
OH
H
H
OH
H
H
OH
O
H
OH
H
H
OH
H
O
H
O
CH2OH
O
H
H
O
CH2OH
O
H
β-Glucan - repeating glucose units
Technical Information - Proteins
Proteins
Proteins are composed of amino acid units. There are 20 different amino acids that occur most
commonly in proteins. Peptide bonds link amino acids to form peptide chains. When the peptide
chain is longer than 10 amino acids, the structure is termed a polypeptide. Proteins are considerably
larger and can be 20,000 amino acids in length.
A tripeptide is shown below. The R-group is different depending on the amino acid.
O
R2
H
O
C
C
N
C
+
H N H2
C
N
C
C
R1
H
O
R3
O
_
Peptides - repeating amino acid units
Berkshire Functional Foods, Special Foods Division, The University of Reading, UK
Carbohydrates 4 + Proteins