Carbohydrates
Carbohydrate Linguistics
 ‘Carbo’ for carbon,
‘hydrate’ for water.
Empirical Formula is
(CH2O)n where n is the
number of carbon atoms
and is ≥ 3.
 Also called ‘saccharides’
after the Greek word for
sugar.
Carbohydrate Uses by the Body
 Used for:
 Cell to cell signaling
when attached to cell
membranes
 Building blocks for
larger molecules
 Energy source
Monosaccharide Chemistry
 AKA the ‘Simple Sugars’,
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mono- for 1 and saccharide
for sugar.
Carbohydrates are either
aldehydes or ketones
depending on which carbonyl
group they possess.
They can be classified based
on the number of carbon
atoms they have and the
suffix ‘-ose’
Hexoses have 6 Carbons…
The carbon atoms are
numbered. *
Common Monosaccharides
Structural Formulae
 Monosaccharides exist as
straight chain molecules,
however when there are
5 or more carbons, the
monosaccharide can also
form a ring structure,
when dissolved in water.
 Ring structures are
usually more conducive
to chemical
reactions/interactions.
Hexoses
 Glucose, Galactose and Fructose are all isomers of one another,
meaning they have the same chemical formula, but a different
structural formula (pages 29-30 in your textbook!).
 As with all isomers, these three sugars possess different
chemical and physical properties.
Ring Structure
 Sometimes there is more than
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one possible ring structure for a
monosaccharide.
The picture on the right is of the
two possible ring structures for
Glucose.
α-Glucose is the isomer of
glucose our body is able to use.
β-Glucose is an isomer of
glucose our body does not
recognize.
Notice the difference between
the two is the placement of the
hydroxyl group on carbon 1.
Monosaccharides and Diet
The body quickly breaks down simple carbohydrates to use as energy. Simple
carbohydrates are found naturally in foods such as fruits, milk, and milk products.
They also occur in processed and refined sugars such as candy, table sugar, syrups,
and soft drinks. The majority of carbohydrate intake should come from complex
carbohydrates (starches) and naturally occurring sugars rather than processed or
refined sugars.
Oligosaccharides
 These are what we call
sugars with 2 carbons
(‘disaccharides’) or 3
carbons
(‘trisaccharides’).
 They are formed in an
anabolic chemical
reaction known as a
dehydration synthesis
reaction.
Common Oligosaccharides
 Maltose is two α-glucose
molecules together…
found in beer.
 Sucrose which is an αglucose and a fructose
together… table sugar.
 Lactose which is an αglucose and a galactose
together… milk sugar.
Maltose formation
 The glycosidic linkage,
the bond between the
sugars, in maltose is
called an  1-4 glycosidic
linkage because it occurs
between carbon 1 of the
first glucose and carbon
4 of the second glucose.
Lactose Formation
 It is an  1-4 glycosidic linkage in lactose as well as the
linkage is between carbon 1 of the glucose and carbon 4
of the galactose.
Sucrose Formation
 The glycosidic linkage in sucrose is called an  1-2
glycosidic linkage because it occurs between carbon 1
of the glucose and carbon two of the fructose.
Polysaccharide Information
 AKA ‘Complex Carbohydrates’,
poly- many and saccharide for
sugar.
 These are hundreds to
thousands of monosaccharides
held together by glycosidic
linkages.
 Some are straight chained,
others are branched, while some
have side groups attached.
 Primarily used as carbohydrate
storage, long-term energy
source. Some are also used for
structural support of the
cell/organism.
Starch
 It is the primary carbohydrate
storage of plants.
 It is composed of two types of
polysaccharides:
 Amylose which is a straight
chain of α-glucose molecules in
α 1-4 glycosidic linkages and
Amylopectin which has a main
chain of α-glucose in α 1-4
glycosidic linkages and branches
of α-glucose off the main chain
in α 1-6 linkages at the branch
points.
AMYLOSE
AMYLOPECTIN
Starch
 Starch is insoluble in water due
to the angles of the glycosidic
linkages. It is stored primarily in
chloroplasts and some fruit of
plants.
 Humans are able to break these
glycosidic linkages to get at the
energy in Starch.
AMYLOSE
AMYLOPECTIN
Glycogen
 It is the long term energy
storage molecule in
animals. Any glucose we
do not use as energy gets
stored as glycogen.
 It is very similar to
Amylopectin, but with
more branching.
 Glycogen is stored in the
liver and our muscles.
Cellulose
 Cellulose is found in
plant cell walls. It is
used for structural
support.
 It is a straight chain of
β-glucose held
together by β 1-4
glycosidic linkages.
Every second glucose
molecule is inverted
(upsidedown).
Cellulose
 Cellulose does not branch
or coil. Cellulose chains
pack close together
because hydrogen bonds
form between the hydroxyl
groups of an inverted
glucose and the hydroxyl
group of a normal glucose.
Cellulose
 We cannot digest cellulose,
as the enzymes in our body
only are able to hydrolyze
 1-4 glycosidic linkages,
but cellulose is an
important part of our diet
because it clears out our
digestive tract (fibre!).
Chitin
 Chitin is the material that makes up the exoskeletons of many
arthropods. It is similar to cellulose however its monomers are
glucose with a nitrogen group attached to the second carbon.
 Again due to the β-glucose, we cannot break it down for energy.
 Chitin is used in contact lenses and biodegradable stitches.
Polysaccharides and Diet
Complex carbohydrate foods provide vitamins, minerals, and fiber that are important to the health
of an individual. The majority of carbohydrates should come from complex carbohydrates (starches)
and naturally occurring sugars, rather than processed or refined sugars, which do not have the
vitamins, minerals, and fiber found in complex and natural carbohydrates. Refined sugars are often
called "empty calories" because they have little to no nutritional value.