Carbohydrates
General molecular formula:
Cn H2n On
1 : 2
: 1
When we say macromolecules what does that mean?
It means huge molecular mass (hundreds or thousands of
units joined together to form one huge molecule)
What is a Monomer?
Is the individual unit of a long chain, that keeps repeating
e.g.: glucose
What is a Polymer?
Is a long chain of repeated units (monomers)
e.g.: Amylose
Monosaccharides
C6 H12 O6
α- glucose
6
5
1
4
3
2
α- glucose
β-glucose
6
5
1
4
3
2
β-glucose
What are the Functions (importance) of glucose?
1.
Through glycolysis and cellular respiration, glucose is
oxidized to eventually form CO2 and water yielding
energy mostly in the form of ATP.
C6H12O6 + 6 O2
2.
→ 6 CO
2
+ 6 H2O + Energy (ATP)
Enters in the formation of disaccharides (maltose,
lactose and sucrose), It is also the monomer in the
formation of starch, glycogen and chitin, as well as the
precursor of vitamin C.
Monosaccharides
Galactose
Is a monosaccharide hexose sugar, also called brain sugar.
Found in dairy products, in sugar beets and other gums.
Monosaccharides
Fructose
Is a monosaccharide hexose sugar (six carbon atoms).
Found in Honey, tree fruits, berries, melons, and some root
vegetables, such as beets, sweet potatoes, and onions.
Monosaccharides End
CH2OH
l
O
OH
l
l
OH
l
l
OH
l
OH
l
OH
Disaccharides
C12H22O11
Maltose
Found in barley (malt) and is used in the production of malt
drinks and brewing beer.
Disaccharides
Lactose
Found in milk and dairy products.
Disaccharides
Sucrose (α1-2 glycosidic linkage)
Table sugar is Found in sugar cane, sugar beets, and sugar
maple trees.
Disaccharides
Maltose = Glucose +
Glucose
Lactose =
Glucose + Galactose
Sucrose =
Glucose + Fructose
Disaccharides End
Polysaccharides
(C6H10O5)n + H2O
Amylose (straight chain, coiled) (H2O insoluble)
α1-4 glycosidic linkage
*The angle at which the α 1-4 glycosidic linkage
forms, results in the coiling of the polymers
Polysaccharides
Amylopectin (Branched) (H2O insoluble)
α1-4 glycosidic linkage (the main chain)
α1-6 glycosidic linkage (at the branch points)
Polysaccharides
Starch is a mixture of both Amylose and
Amylopectin (H2O insoluble)
i.e.: Amylose + Amylopectin = Starch
*plants store excess glucose as starch
in chloroplasts, amyloplasts and other plastids.
*Starch is found in plants like potatoes, rice,
wheat, and corn which constitute a major
source of starch in the human diet.
Polysaccharides
Glycogen (highly branched) (H2O insoluble)
α1-4 glycosidic linkage (the main chain)
α1-6 glycosidic linkage (at the branch points)
Glycogen has the same structure as amylopectin,
however it is more branched.
*Animals store excess glucose as glycogen
*Glycogen is broken back down into glucose when
energy is needed (a process called
glycogenolysis).
Polysaccharides
Cellulose (straight chain) (H2O insoluble)
β1-4 glycosidic linkage
*The hydroxyl groups at the 1-4 positions in β glucose
cause every other monomer to be inverted for the
glycosidic linkage to form, this results in the straightness
of the polymer, which allows hydroxyl groups of parallel
molecules to form many hydrogen bonds , producing tight
bundles called microfibriles.
Polysaccharides
Chitin (H2O insoluble)
Is a cellulose-like polymer, the monomer is a glucose
molecule to which a nitrogen-containing group is
attached to the second carbon atom.
*Chitin forms the exoskeleton of crustaceans, such
as crabs, lobsters and the cell wall of some fungi.
What are the main two functions of polysaccharides?
1. Energy storage:
 Starch is stored in the chloroplasts, amyloplasts and
other plastids of plants.
 Glycogen is stored in muscle cells and liver cells, and
enzymes in these tissues hydrolyze glycogen into single
glucose molecules that are used for energy.
2. Structural support:
 Cellulose microfibrils interlace and form a meshwork
that supports plant cells (the cell wall).
 Chitin forms the exoskeleton of crustaceans, such as
crabs, lobsters and the cell wall of some fungi.
The cellulose cell wall & the chitin exoskeleton
Cell wall
Exoskeleton
Polysaccharides End