Carbohydrates
Structures and Functions
Carbohydrates
• Named so because many have formula Cn(H2O)n
• Produced from CO2 and H2O via photosynthesis in plants
• Range from as small as glyceraldehyde (Mw = 90 g/mol) to as large as
amylopectin (Mw > 200,000,000 g/mol)
• Fulfill a variety of functions including:
– energy source and energy storage
– structural component of cell walls and exoskeletons
– informational molecules in cell-cell signaling
• Can be covalently linked with proteins to form glycoproteins
and proteoglycans
Size classes of carbohydrates
• Monosaccharides (simple sugars): one polyhydroxy aldehyde or
ketone unit.
– D-glucose: the most abundant monosaccharide in nature
– Monosaccharides of 4C or more tend to have cyclic structures
• Disaccharides: two monosaccharide units joined together by a
glycosidic linkage (e.g. sucrose)
- All common mono- and di-saccharides have names ending with the
suffix “-ose”
• Oligosaccharides: a few monosaccharide units covalently joined
by glycosidic bonds (in cells, most oligosaccharides are joined to
non-sugar molecule)
• Polysaccharides: sugar polymers consisting of >20 monosaccharide
units
, Monosaccharides Aldoses
• Functional group:
aldoses and ketoses
- An aldose contains an aldehyde functionality
- A ketose contains a ketone functionality
• Carbon backbone:
- 3C → triose
- 4C → tetrose
- 5C → pentose
- 6C → hexose
- 7C → heptose
Monosaccharides: Stereochemistry
• All monosaccharides (except dihydroxyacetone) are chiral compounds,
with at least one chiral carbon
• A chiral (asymmetric) carbon is a carbon atom that is attached to four
different types of atoms or groups of atoms
Structures and Functions
Carbohydrates
• Named so because many have formula Cn(H2O)n
• Produced from CO2 and H2O via photosynthesis in plants
• Range from as small as glyceraldehyde (Mw = 90 g/mol) to as large as
amylopectin (Mw > 200,000,000 g/mol)
• Fulfill a variety of functions including:
– energy source and energy storage
– structural component of cell walls and exoskeletons
– informational molecules in cell-cell signaling
• Can be covalently linked with proteins to form glycoproteins
and proteoglycans
Size classes of carbohydrates
• Monosaccharides (simple sugars): one polyhydroxy aldehyde or
ketone unit.
– D-glucose: the most abundant monosaccharide in nature
– Monosaccharides of 4C or more tend to have cyclic structures
• Disaccharides: two monosaccharide units joined together by a
glycosidic linkage (e.g. sucrose)
- All common mono- and di-saccharides have names ending with the
suffix “-ose”
• Oligosaccharides: a few monosaccharide units covalently joined
by glycosidic bonds (in cells, most oligosaccharides are joined to
non-sugar molecule)
• Polysaccharides: sugar polymers consisting of >20 monosaccharide
units
, Monosaccharides Aldoses
• Functional group:
aldoses and ketoses
- An aldose contains an aldehyde functionality
- A ketose contains a ketone functionality
• Carbon backbone:
- 3C → triose
- 4C → tetrose
- 5C → pentose
- 6C → hexose
- 7C → heptose
Monosaccharides: Stereochemistry
• All monosaccharides (except dihydroxyacetone) are chiral compounds,
with at least one chiral carbon
• A chiral (asymmetric) carbon is a carbon atom that is attached to four
different types of atoms or groups of atoms
