CARBOHYDRATES
hydrated carbon Cx(H2O)y
classified by
o the number of repeating units (monomers) monosaccharide, disaccharide, and polysaccharide
o the type of monomers of which they consist and the type of bonds between monomers
Monosaccharides (aldose, ketose)
a single monomer; Molecular formula of monosaccharides (CH2O)n
All carbons in a monosaccharide are bonded to a hydroxyl group (-OH) except for one which is bonded to a
carbonyl group (=O)
o Aldose = aldehyde sugar carbonyl group on an end carbon  CH(OH) CHO
o Ketose = ketone sugars carbonyl group on a interior carbon  CH(OH) C(O)  CH(OH)
Ring form
o Most common monosaccharides form rings in aqueous solutions
o Note how the ring and linear forms of a sugar interconvert; this interconversion goes on naturally in
biological systems even without the help of enzymes, but is frozen in place upon the formation of sugar
polymers such as dissacharides
Glucose (hexose = 6 carbons)
o Glucose is the most common monosaccharide
o Glucose is an aldose
Ä…-D-glucose ²-D-glucose
:
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Disaccharides
o Two monosaccharides connected by glycosidic linkage
o produced from a dehydration (condensation) reaction:
o Common disaccharides
Maltose = glucose + glucose (starch breakdown product)
Lactose = glucose + galactose
Sucrose = glucose + fructose (glucose + fruit sugar =  plant sugar )
o Used for transport and short term energy storage
require specific enzymes to break glycosidic linkages
Polysaccharides
o polymers of monosaccharides (>10 monomers)
o Polysaccharides typically serve as
carbon and energy storage molecules: starch (plants), glycogen (animals)
structural material: cellulose (plants), chitin (insects)
Energy Storage
Starch only glucose monomers connected by Ä… 1-4 linkages (more easily hydrolysed)
o Amylose = unbranched starch (only 1-4 linkages)
o Amylopectin = branched starch (found in plants)
o Glycogen = heavily branched starch (found in animals)
" Branches are 1-6 linkages; branched starches contain both 1-4 and 1-6 linkages, creating a
very large,  fluffy molecule
Structural Polysaccharides
Cellulose linear polymer of glucose, connected by ² 1-4 linkages (NOT easily hydrolysed)
o cell walls, wood
o Most organisms cannot digest (hydrolyze) cellulose; digestive tract microorganisms (cows, termites) and
many fungi can
Chitin
o Chitin is found in the exoskeletons of insects, spiders, and crustaceans and the cell walls of fungi
o Chitin is leathery in pure form but is hardened in most uses via the deposition of calcium carbonate
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