Bio molecules
1. Carbohydrates
2. Protein and enzymes
3. Lipids
4. Nucleic acids
Carbohydrates
• Most abundant class of
biological molecules on Earth
• Originally produced through
CO2 fixation during
photosynthesis
General characteristics
• the term carbohydrate is derived from the french:
hydrate de carbone
• compounds composed of C, H, and O
• empirical formula - CH2O)n when n = 5 then
C5H10O5
• not all carbohydrates have this empirical formula:
deoxysugars, aminosugars
• carbohydrates are the most abundant compounds
found in nature (cellulose: 100 billion tons annually)
General characteristics
• Most carbohydrates are found naturally in bound
form rather than as simple sugars
• Polysaccharides (starch, cellulose, inulin, gums)
• Glycoproteins and proteoglycans (hormones, blood
group substances, antibodies)
• Glycolipids (cerebrosides, gangliosides)
• Glycosides- sugar is bound to another functional
group via a glycosidic bond eg. Saponin, coumarin
• Mucopolysaccharides (hyaluronic acid)
• Nucleic acids
Roles of Carbohydrates
• Energy storage (glycogen,starch)
• Structural components (cellulose,chitin)
• Cellular recognition
• Carbohydrate derivatives include DNA, RNA,
co-factors, glycoproteins, glycolipids
Carbohydrates
• Monosaccharides (simple sugars) – glucose,
fructose
• Disacharides - ,sucrose, lactose
• Trisaccahride – trehalose, raffinose
• Oligosaccharides = - usually 2 to 10
• Polysaccharides are polymers of the simple
sugars – starch, cellulose, glycogen
Monosaccharides
• Aldoses and ketoses
• Empirical formula = (CH2O)n
Aldoses
O
ketoses
H
C
CH2OH
H
C*
OH
HO
C*
H
H
C*
OH
CH2OH
D-ribose
C
O
HO
C*
H
H
C*
OH
CH2OH
D-ribulose
Aldoses
ketoses
Monosaccharides are chiral
• Number of possible
steroisomers = 2n (n = the
number of chiral carbons)
O
H
C
CH2OH
H
C*
OH
HO
C*
H
H
C*
H
C*
C
O
HO
C*
H
OH
H
C*
OH
OH
H
C*
OH
CH2OH
D-glucose
CH2OH
D-fructose
Stereochemistry
Enantiomers
O
H
O
C
O
H
C
HO
C*
H
H
C*
OH
HO
C*
HO
C*
Epimers
Diastereomers
O
H
C
C
C*
OH
HO
C*
H
H
C*
OH
HO
C*
H
HO
C*
H
HO
C*
H
H
C*
OH
H
C*
OH
HO
H
H
C*
OH
H
C*
OH
H
CH2OH
L-glucose
D-glucose
O
H
C
H
CH2OH
O
H
H
C
H
C*
OH
HO
C*
H
H
HO
C*
H
HO
C*
H
C*
H
H
C*
OH
H
C*
OH
C*
OH
H
C*
OH
H
C*
OH
CH2OH
CH2OH
D-mannose
D-galactose
CH2OH
D-glucose
CH2OH
D-mannose
•Enantiomers = mirror images
•Diastereomers - Pairs of isomers that have opposite
configurations at one or more chiral centers but are
NOT mirror images are
•Epimers = Two sugars that differ in configuration at
only one chiral center
Enantiomers and epimers
H
H
H
H
C
O
H
C
OH
H
C
OH
CH2OH
C
O
C
O
C
O
HO
C
H
HO
C
H
OH
C
H
HO
C
H
HO
C
H
OH
C
H
H
C
OH
HO
C
H
H
C
OH
H
C
OH
CH2OH
these two aldotetroses are enantiomers.
They are stereoisomers that are mirror
images of each other
CH2OH
CH2OH
these two aldohexoses are C-4 epimers.
they differ only in the position of the
hydroxyl group on one asymmetric carbon
(carbon 4)