Chapter 7 Recommended Work
• Within Chapter “Worked Examples” – take a look at those!
• End of Chapter Problems: 1, 2, 4, 8, 13, 14, 15, 19, 21, 26
• Of course, the Achieve Stuff…
Carbohydrates
• Carbohydrates are the most abundant biomolecules on earth
• More than half of all “organic” carbon is found in carbohydrates
• The majority contain Carbon, Hydrogen, and Oxygen in the ratio Cn(H2O)n
• We will discuss carbohydrates and glycoconjugates (things sugars are attached to)
• “Saccharides” = sugars. Most have a chiral center
• Monosaccharides (Glucose, for example)
• Disaccharides (Sucrose, for example)
• Oligosaccharides (a few)
• Polysaccharides (Many)
The Importance of Carbohydrates
Of course, not everything can breakdown all carbs. Why?
The Importance of Carbohydrates
The Importance of Carbohydrates
• “Saccharide” – (Greek) = sweet taste
• One of the characteristics of sugars is that they taste sweet
(some artificial sweeteners are AAs (aspartame) and taste
bitter to some people).
• Sweetness is a subjective interaction between a chemical
and taste receptors (proteins) in your mouth
• Sweet receptor is a GPCR (stay tuned) encoded by two genes
called TAS1R2 and TAS1R3
Stereochemistry matters!

Monosaccharides: Trioses
• The simplest carbohydrates (monosaccharides) are the Trioses
• They have three (3) carbons (name)
• They exist in two types: Aldoses and Ketoses
• Why are they named this way?
• Remember these!
- Aldose CHO / aldehydes
- Ketose C=O / Ketones
Glyceraldehyde = 3 carbon = aldotriose
Dihydroxyacetone = 3 carbon = ketotriose
Monosaccharides: Hexoses
• Hexoses
• They have six (6) carbons (name)
• They exist in two types: Aldoses and Ketoses
• Why are they named this way?
• Remember these!
• Glucose is a part of sucrose (table sugar)
• Fructose is a part of fruit sugar
• Most common monosaccharides
Monosaccharides: Pentoses
• Pentoses
• They have five (5) carbons (name)
• They exist in two types: Aldoses and Ketoses
• Why are they named this way?
• Remember these!
• D-ribose is found in RNA
• 2-Deoxy-D-ribose is found in DNA
OH
Stereochemistry of Monosaccharides
Need: CHIRALITY
Chirality  4 *different* substituents around the carbon
n chiral centers: 2n stereoisomers; 4 chiral centers = 16
In human = D
24
Aldoses with 3C or more; Ketoses with 4C or more
ARE CHIRAL (D,L system)
1. Enantiomers differ at all stereocenters, and are therefore
mirror images of each other (D- and L-glyceraldehyde)
2. Diastereomers are non-mirror image stereoisomers. They
occur when a compound has different configurations of
one or more (but not all) of the equivalent stereocenters.
(D-altrose and D-glucose)
Stereochemistry of Monosaccharides
• The stereoisomers of monosaccharides are classified as “D” or “L” based on the
configuration of the chiral carbon farthest from the carbonyl, with reference to D/L
glyceraldehyde
• In nature, most monosaccharides are “D” but there are some naturally occurring “L”
monosaccharides
1. Find the highest numbered
chiral carbon. Here, #2.
2. If the OH is on the right, D
3. If the OH is on the left, L
Stereochemistry of Monosaccharides
Enantiomers
Enantiomers – different configuration
at all chiral centers
Enantiomers
Diastereomers – different
configuration at not all chiral centers
Epimers – different configuration at
only one chiral center
Configuration change only at
C5
Configuration change only at
C5
L-sorbose is an epimer
(diastereomer) of D-Fructose
L-Idose is an epimer
(diastereomer) of D-glucose
Green box is
the chiral
center farthest
from the
carbonyl.
This is where
we determine
D vs L.
Try to identify
which are
diastereomers
and which are
epimers for
practice.
Know the
starred sugars.
How many
C’s?
Ald or Ket?
D-Aldoses
D-Ketoses
Know the starred
sugars. How many C’s?
Aldose or Ketose?
Monosaccharides
PREVIOUS TWO SLIDES
Sugars form Rings: The Cyclization of Sugar
An aldehyde and an alcohol
can react to form a
hemiacetal.
If another alcohol is available,
the reaction can happen again
to form an acetal.
This same theme can happen
with ketones.
This is important because
monosaccharides have
aldehyde groups (aldoses), or
ketone groups (ketoses), and
alcohols!
These groups can react with
themselves, in the same
molecule, and cyclize!
Sugars form Rings: The Cyclization of Sugar
• Cyclization takes place as a result of interaction between the functional groups of
distant carbons
• Between C-1 and C-5
To form a cyclic hemiacetal in aldohexoses
Fisher
• Between C-2 and C-5
To form a cyclic hemiketal in ketohexoses
Haworth
Sugars form Rings: The Cyclization of Sugar
• The carbonyl carbon becomes a new chiral center called the anomeric carbon
• Therefore, cyclic forms possess anomeric carbons, and the cyclic α and β forms are
anomers of each other
Tips:
For D-sugars: CH2OH  up
α  OH down
β  OH up
For L-sugars: CH2OH  down
α  OH up
β  OH down
Mutarotation:
Interconversion of
anomers in aqueous
solution.
For all:
α: OH opp. CH2OH
β: OH same side CH2OH
Anomers
Pyranoses and Furanoses
Furan = Five
Some Important Hexose Derivatives
Don’t memorize all of
these.
You’ll be seeing these
a few times in the
future.
Remember:
N-acetyl-β-Dglucosamine
(bacterial cell walls,
and other things)
Sugars as Reducing Agents
Many sugars (including
glucose) are reducing agents!
The carbonyl (aldehyde or
ketone) can be oxidized
For example, the linear form
of D-glucose can participate
in REDOX reactions.
An example of this is an older
way of testing blood glucose.
Fehling’s Reaction
What is a hemiacetal?
A hemiacetal, when opened up, forms an aldehyde,
which can be oxidized
Find the carbon, see what is attached to it
If hemiacetal: “reducing end”
If not, not reducing
Measuring [Blood glucose]
Turns blood “brown”
Oxidizes glucose
Measure the color
change
Another way to measure [Blood glc]
Measuring something
different…
Glucose reacts with
Hemoglobin to form “glycated
hemoglobin (GHB)”
A.K.A. “A1c”
Gives a broader picture of your
“glucose habits”
From Monosaccharides to Disaccharides (and more!)
• Monosaccharides can form di- and poly-saccharides through glycosidic bonds!
• Two sugar molecules can be joined via a glycosidic bond between an anomeric
carbon and a hydroxyl carbon
Disaccharides: Glycosidic Bonds
These glycosidic bonds are numbered
The numbers (ex: 14) refer to the carbons involved in the bond. 1 is the anomeric
carbon. 5/6 is the CH2OH carbon.
Multiple linkages are possible between the same monosaccharides.
Enzymes are specific for these linkages.
Humans cannot digest most β-glycosidic bonds.
For all:
α: OH opp. CH2OH
β: OH same side CH2OH
Other Disaccharides
Polysaccharides!
• “Poly” (many) “saccharide” (sugar)
• Polysaccharides are carbohydrates made up of many sugars bound together
• Major Functions: Storage, Structure, Recognition (cell-cell recognition)
• Starch and Glycogen are storage (energy) molecules
• Chitin and Cellulose are structural molecules
• Cell surface polysaccharides are recognition molecules
• Nomenclature: Homopolysaccharide vs. Heteropolysaccharide
• These are also known as “glycans”
Polysaccharides!
In nature, most
carbohydrates exist
as polysaccharides
Homo/Hetero
Linear/Branched
Glucose is usually
tied up in a large
polysaccharide
Polysaccharides – Why?
Polysaccharides – Why?
If Glc was free…
[Glc] inside the
cell is less than
outside.
Cell
Glc tends to move
into the cell.
Blood
Cell
[Glc] inside the
cell is greater
than outside.
Glc cannot move
into the cell.
Storage Homopolysaccharides – Starch (큰 당)
• Starch (in plants) is composed of two polysaccharides:
• Amylose: unbranched glucose polymer (α14 linkage)
• Amylopectin (also glucose): linear parts (α14 linkage)
• Branches out every 24-30 residues (glucoses) using α16 linkages
Starch granules are thought to be clusters
of amylose and amylopectin
Double helical structures can form
Non-reducing end glucose sugars are
removed sequentially.
Storage Homopolysaccharides – Starch (Glycogen)
• Main storage polysaccharide in animals
• Greatest abundance in liver and muscle cells
• Similar in structure to amylopectin, but with more branch points
• Unbranched glucose polymer (α14 linkage)
• Branches out every 8-12 residues (glucoses)
using α16 linkages
• It is more compact. Why?
Glycogen
Why Branching?
Glycogen
Structural Homopolysaccharides – Cellulose
• Cellulose is the primary structural component of plant cells
• Most abundant polysaccharide in nature
• Unbranched: 10,000-15,000 glucose monomers
• β-(1-4)-linked glucose (previous polymers were α glucoses); water-insoluble, tough
• Starch was a tightly coiled helix, cellulose is a straight chain
• Wood (50% cellulose), Paper (90%), Cotton (90%)
How is Cellulose so Strong?
β-(1-4)-linked glucoses allow for the
formation of hydrogen bonds
Most animals do have the α-amylase enzyme to digest amylose (starch)
Structural Homopolysaccharides - Chitin
(KY-tin)
(Told you on slide #20 to remember this one)
Arthropods (crustaceans - subphylum)
Structural Heteropolysaccharides - Peptidoglycan
• Peptidoglycans: rigid component of bacterial cell walls
• Alternating monosaccharides (repeating disaccharides)
• Peptide-cross-linked linear polysaccharides
• Penicillin and related antibiotics block synthesis
Repeating Disaccharide
Amino acid
Structural Heteropolysaccharides – Glycosaminoglycans (GAGs)
• Repeating disaccharides (…ABABAB…) with an amino side-group
• No cross-links
• Components of the gel-like extracellular matrix (ground substance – connective)
• Highly polar molecules  attract water  lubricant/shock absorbers
• Examples: hyaluronan, chondroitin sulfate, keratan sulfate, heparin
Structural Heteropolysaccharides – Glycosaminoglycans (GAGs)
Viscous lubricants in
synovial fluid (joints);
vitreous humor
Glycoconjugates
• Information carriers, consisting of “anchors” embedded in the cell membrane, plus
oligo- or polysaccharides (floating outside of the cell membrane – into the ECM)
Glycoconjugates - Proteoglycans
• Core protein + glycosaminoglycans
• Found of the cell surface or in extracellular matrix
• 1 or more glycosaminoglycan chain(s) covalently bound to a core protein
• The glycosaminoglycan is often the main site of biological activity
Proteoglycan Aggregates
ECM component
Absorbs/release large
amounts of water
(polarity)
Functions as “shock
absorber”
Glycoproteins
• Glycoproteins: proteins covalently linked to carbohydrates through N- or O-linkages
• Protein + 1 or more oligosaccharide(s)
• Carb components are smaller/more structurally diverse than in proteoglycans
• Cell surface/ECM
• Hormones, Immunoglobulins (IGs)
O-Linkage:
Between hydroxyl groups
of serine or threonine and
N-acetylgalactosamine
N-Linkage:
Between asparagine and
N-acetylglucosamine
Glycolipids and Lipopolysaccharides
(components of cell membranes)
• Glyco(sphingo)lipids (사람)
• Oligosaccharides covalently bound to lipids via a
glycosidic linkage
• On the outer surface of plasma membranes
• Often binding sites for proteins (antigens, blood group
determinants)
• Lipopolysaccharides (LPS) – 세균
• Dominant surface feature of gram-negative bacteria (E. coli,
Salmonella enterica)
• Endotoxin (released when bacteria dies 
inflammatory/immune response)
• Prime targets of antibodies
Glycolipids – Blood Groups
O antigen oligo is the core.
This is a glycosphingolipid.
Type O gene does not produce an
enzyme  nothing added
Type A glycosyltransferase adds Nacetylgalactoseamine to the core.
(Type A gene codes for this enzyme)
Type B glycosyltransferase adds
galactose to the core. (Type A gene
codes for this enzyme)
Carbohydrates and Informational Molecules
Lectins
• Proteins that specifically and strongly bind carbohydrates (usually attached)
• Found in all organisms.
• Serve a wide variety of cell-cell recognition, signaling, and adhesion processes
(CAMs)
• Human selectins mediate the inflammatory response (RA, asthma, psoriasis, MS,
transplant rejection) – and are therefore potential drug targets
• P-selectins on endothelial cells and oligosaccharides on leukocytes
Lectins and Viral Infections
• The cell membrane is covered in glycoproteins. Some proteins are “decorated” with a
carbohydrate called neuraminic acid (sialic acid). Neu5Ac is typical. – 사람 세포
• Influenza has a receptor-binding membrane fusion glycoprotein (lectin) called
Hemagglutinin (HA) and it binds to sialic acid attached glycoproteins
• AND a neuraminidase (NA) which clips sialic acid off of the glycoprotein
Neuraminidase Inhibitors – Oseltamivir (Tamiflu)
Competitive Inhibitor!
Lectins and Human Health
Linked to all kinds of
cancer, ulcers,
inflammation, etc.
Pharmacological tools: PTx
blocks Gi  can’t turn off AC
(cAMP)
CTx leaves AC on (cAMP)
 Sodium and water out 
diarrhea (death?)
Lectin Mechanisms