Carbohydrates
► One
of the most common organic materials on
Earth
► They are:
 A source of energy
 building material
 cell surface markers for cell-to-cell
communication and identification
 Made of carbon, hydrogen and oxygen in ratio 1:2:1.
(CH2O)

Includes sugars, starch, glycogen, and cellulose.
Monosaccharide
simplest carbohydrates
Carbonyl group
(Mono – one , saccharide – sugar)
► Have the common formula (CH2O)n
► Simple sugars ( e.g. glucose C6H12O6)
► Nearly all organisms use glucose
as a source of energy
 Possess carbonyl group (functional group composed of a
carbon atom double-bonded to an oxygen atom : C=O )
 Named by the number of carbon atoms: three carbon
sugars are called trioses, five carbon sugars pentoses, and
six carbon sugars are hexoses. (See Handout)
►
► Disaccharide
– A double sugar formed by
joining two monosaccharides by dehydration
synthesis.
► Oligosaccharide – monosaccharide
polymers containing three to ten simple
sugars attached to one another by covalent
bonds called glycosidic linkages.
► Polysaccharide
–Long chain of repeating
sugar units formed by joining simple sugars
by dehydration synthesis (e.g. cellulose,
chitin, glycogen)
► Starch
– a polysaccharide formed from the
alpha glucose units. It is the main food
storage compound in plants. Glycogen is
the form of carbohydrate storage in
animals.
Isomers
► chemicals
that have the same chemical
formula but a different arrangement of
molecules
► E.g. glucose, galactose and fructose are
isomers because they have the same
molecular formula C6H12O6 but different
structural arrangements.
► Isomers possess different shapes and
different physical and chemical properties.
Isomers
►
propanol: it has the formula C3H8O (or C3H7OH)
and occurs as two isomers: propan-1-ol (n-propyl
alcohol; I) and propan-2-ol (isopropyl alcohol; II)
► Questions
P. 34 # 2 , 3 , 4
► Handout Questions