Download Biochemical Polymers

An Introduction
W.T. Winter
[email protected]
215 Jahn Lab; x6876
Overview
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Monosaccharides?
Oligosaccharides?
Polysaccharides
Glycoproteins and Proteoglycans
Carbohydrates Are Chiral
Molecules
Typically but not always
• L – amino acids
D
• D - sugars
Hence, these molecules
have a measurable optical
rotation, which depends
upon both the monomer
residues and their
conformation
L
Glyceraldehyde
Fisher Formulas
Next to last
carbon
determines
D or L
New carbon is added as C1
A Way to Explore Monosaccharides
• John Maser at Leeds has developed a
“Monosaccharide Browser” the site is
http://www.beechtreecommon.org/biochem
istry/monosaccharide/
Epimers Differ by Configuration at
One Chiral Center
D-glucose
C2 epimer
D-mannose
C3 epimer
D-allose
C4 epimer
D-galactose
C5 epimer
L-idose
Sugars Prefer To Be Cyclic
Hemiacetals and Cyclization Group
b-D-Glucose
• In nature, open chain
forms are rare.
• NMR has shown that
all 5 coexist with the
pyranose forms
occurring 99% of the
time, furanose about
0.5% each and a
trace of open chain
a and b are “anomers
and differ in
configuration at the
new chiral center
formed in the cycle
Pyranose Ring Shapes
Pyranose rings can form chair and boat
conformers
1C
4
4C
1
Sucrose
• 1-2 linked alpha
glucose, beta fructose
• Sources sugar cane
sugar beet
Polysaccharides
• Polysaccharides consist of sugar residues
linked into a polymer.
• Polysaccharides, unlike proteins or nucleic
acids, are not always linear in sequence
• The most abundant biomolecules in
nature-about 1012 tons of cellulose are
synthesized each year
• Functions: structural, food storage, cell
surfaces, extracellular matrices.
Polysaccharides May Be the Most
Diverse Biomolecules
From one 6 carbon
hexopyranose sugar
such as glucose, you
can make 11 different
disaccharides and 8
of those lead to
infinite polymers
From one amino acid or
nucleotide you can
make only a single
dimer.
CH2OH
CH2OH
o
o
OH
OH
OH
OH
OH
OH
a-D-Glucose
OH
OH
b-D-Glucose
Cellulose: Structural
polysaccharide from glucose
n ~ 5000-10000
Also found in some
bacteria, algae, fungi,
seed hairs, and
animals (tunicates or
sea squirts)
Microfibrils
of cellulose
Wood cell (fiber) cell walls
are made of cellulose +
lignin and hemicelluloses
Starch: a-D-Glucose polymer found
as an energy storage material in
foods
Unlike cellulose,
starch can be
metabolized by
humans.
Starches provide
the bulk of the
energy we obtain
from grains,
potatoes etc.
Amylose
Amylopectin
Extracellular Matrix: Hyaluronic acid
A regular copolymer of N-acetyl glucosamine and Glucuronic Acid (as a metal salt)
HA cont
Found in:
• synovial fluid (knee, shoulder )
• Vitreous humor (eye- used in
reconstructive eye surgery)
• Skin – small amounts in all connective
tissues
Connective Tissues- fibrous
proteins, polysaccharides, and
proteoglcans
Other Structural Polysaccharides
• Mannans – some algae
• Alginic acids – many algae
• Chitin- insects, crustaceans (shrimp shell),
fungi.