3. Lecture Objectives
1: Describe the structural features of monosaccharides.
2: Draw the straight-chain and ring structural formulas of
glucose and fructose.
3: Describe the condensation of monosaccharides to form
disaccharides and polysaccharides.
4: List the major functions of carbohydrates in the human
body.
5: Compare the structural properties of starch and cellulose,
and explain why humans can digest starch but not
cellulose.
6: State what is meant by the term dietary fibre.
7: Describe the importance of a diet high in dietary fibre.
4. • Monosaccharides have an empirical formula
of CH2O
– Many isomers
• Ex: Glucose and fructose have same molecular formula
but have different structures
Glucose
Objective
B.3.1
Describe the structural features of
monosaccharides
5. • Made up of covalent bonds
• Contain one carbonyl group (C=O)
• Contain at least two hydroxyl groups (-OH)
• Ex. Glucose, fructose, and galactose
Objective
B.3.1
Describe the structural features of
monosaccharides
6. Objective
B.3.2
Glucose: Straight-Chain Formula
• 6-carbon backbone
• Carbons 1 and 5 are connected by
Oxygen
• Each carbon is bonded to a
hydroxide (except for the 5th)
– Carbon 1 has a hydroxide on top
– Carbon 3 has a hydroxide on the left
– Carbons 2, 4, and 6 have
hydroxides on the right
• All other bonds are occupied with
Hydrogen
Draw the straight-chain and
ring structural formulas of glucose
and fructose
7. Objective
B.3.2
Glucose: Ring-Structure Formula
• Should be familiar (biology class)
• Hexagon-shape with 5 Carbons
and Oxygen in the top right
corner
• Each carbon bound to 1
hydrogen and 1 hydroxide
– Hydrogen is on top, hydroxide
is on bottom (except Carbon 3)
– Carbon 5 has another carbon(6)
instead of a hydroxide
– Carbon 6 has 2 hydrogens and
1 hydroxide
Draw the straight-chain and
ring structural formulas of glucose
and fructose
The ring-structure forms when
glucose is dissolved in water
and undergoes and internal
reaction
8. Alpha (α) vs. Beta (β)
•Alpha (α) structure has the
hydroxide group on the bottom
bonded with carbon 1 in the ring
structure. (AB)
•Beta (β) structure has the OH
group on the top bonded to carbon
1 in ring structure. (BT)
•The alpha- and beta- variations only occur in
the ring structure
Objective
B.3.2
Draw the straight-chain and
ring structural formulas of glucose
and fructose
9. Objective
B.3.2
Fructose: Straight-Chain
Formula
• 6-carbon backbone
• Carbon 1 and Carbon 6 both
have two hydrogens and 1
hydroxide
• Carbon 2 has one single
Oxygen
• Carbons 3, 4, and 5 all have
one hydrogen, one hydroxide
– Carbon 3 is flipped
(hydroxide on the left)
Draw the straight-chain and
ring structural formulas of glucose
and fructose
C
C
C
C
CH2OH
OH
H
OH
H
H
HO
OH
H
C
glucose
C
C
C
C
CH2OH
OH
H
OH
H
H
HO
fructose
O H
O CH2OH
10. Objective
B.3.2
Fructose: Ring-Structure Formula
• Pentagon-shape with Oxygen at the
top center and 4 other Carbons
• Two bottom Carbons have
one hydrogen and one
hydroxide
• The two side Carbons have
one hydroxide and another
carbon
• Hanging carbons have two
hydrogens and one
hydroxide
Draw the straight-chain and
ring structural formulas of glucose
and fructose
The ring-structure forms when
fructose is dissolved in water
and undergoes and internal
reaction
11. Objective
B.3.2
Draw the straight-chain and
ring structural formulas of glucose
and fructose
Alpha (α) vs. Beta (β)
•Similar to the Alpha and Beta
structures of glucose
•ARB (Alpha (α): on the right of
C2 for straight-chain, on the
bottom for ring structure)
•BLT (Beta (β): on the left of C2
for straight-chain, on the top for
ring structure)
•Note that the fructose
variations occur at C2, and not C1.
12. Objective
B.3.3
• Monosaccharides can join together and form a
disaccharide through condensation (dehydration
synthesis)
• Hydroxyl (-OH) groups of monosaccharides (or
disaccharides)
• Maltose Example (glucose + glucose)
– C6H12O6 + C6H12O6 C12H22O11 + H2O
– Hydrogen from one glucose –OH group and OH from
another glucose’s –OH group are lost as water
– Remaining oxygen up bridges the monomers forming a
disaccharide
– 14 linkage utilizing covalent bond (glycosidic bond)
Describe the condensation of
monosaccharides to form
disaccharides and polysaccharides.
19. Objective
B.3.4
• Energy Source: Glucose
–Glucose is a monosaccharide which
helps provide the body with energy
–Glucose is oxidized in respiration to help
form ATP energy for the body to use
List the major functions of
carbohydrates in the human body
http://www.individualsole.com/wp-content/uploads/2010/05/SpSu10_Running_02035_ipod-540x360.jpg
20. Objective
B.3.4
List the major functions of
carbohydrates in the human body
http://drpinna.com/wp-content/uploads/2010/08/glucose.gif
21. Objective
B.3.4
• Energy Storage: Glycogen
– Energy, in animals, is stored in the
form of Glycogen (in the liver
muscles)
– Glycogen is formed through
Glycogenesis when there’s an
abundance of glucose in the body
– The polysaccharide Glycogen
breaks down through
Glycogenolysis when more energy
is needed
List the major functions of
carbohydrates in the human body
http://findstorageauctionriches.com/IMAGES/self-storage-units.jpg
22. Objective
B.3.4
List the major functions of
carbohydrates in the human body
http://themedicalbiochemistrypage.org/images/glycogen.jpg
23. Objective
B.3.4
• Carbs are Important for
Other Molecules!
– Carbs can be precursors to the formation of
other molecules
– EX. Glucose
– Glucose is needed to produce Vitamin C ,
proteins, and in forming disaccharides and
polysaccharides
– In Glycolysis, glucose undergoes
phosphorylation which allows it to be a
precursor
– Carbs are also involved in structure/support
in plants especially (EX. Cellulose which is
formed from glucose)
List the major functions of
carbohydrates in the human body
http://upload.wikimedia.org/wikipedia/commons/8/81/Ascorbic_acid_structure.png
Ascorbic Acid (Vitamin C)
24. Objective
B.3.5
Compare the structural properties of starch
and cellulose, and explain why humans can
digest starch but not cellulose.
•Cellulose and Starch are
both polymers of glucose
•The ring structure of
glucose has two orientations
• α- Glucose
•OH group on the carbon
1 and the CH2OH group
on the carbon 5 point in
opposite directions
•β - Glucose
• OH group and CH2OH
group point in the same
direction
25. – Starch
• Polysaccharide
– Created with a chain α- Glucose units
– Bridging O atom is on the opposite
side of the CH2OH group
• Serves as food storage in plants
– Corn, potatoes, wheat, and rice contain
starch
• Two forms of Starch
– Amylose
» Straight chain polymer between
the 1,4 carbons of the α- Glucose
units (unbranched)
– Amylopectin
» Branched structure that has both
α- 1,4 linkage and α- 1,6 linkage
– The two forms of starch allow it to be a
relatively compact spiral structure
stored as starch grains in plant cells.
Objective
B.3.5
Compare the structural properties of starch
and cellulose, and explain why humans can
digest starch but not cellulose.
26. • Cellulose
– Polysachharide
– Created with a unbranched chain β - Glucose units
– Bridging O atom is on the same side as the CH2OH group
– Β- 1,4 linkage
– forms uncoiled linear chains due to the “upside down”
alternating glucoses
– Hydrogen Bonds
– These form cables known as microfibrils which are rigid and
give support to plants and make wood a useful building material
Objective
B.3.5
Compare the structural properties of starch
and cellulose, and explain why humans can
digest starch but not cellulose.
27. • Enzymes that break down starch cannot always break down cellulose because
of their structural differences
• In humans, starch can be hydrolyzed to glucose and oxidized into energy
– Cellulose passes through the body unchanged
– Some animals and bacteria contain enzymes to digest cellulose as a food
source
– Cellulase breaks down the beta glycosidic bonds. Humans do not produce
this enzyme
Objective
B.3.5
Compare the structural properties of starch
and cellulose, and explain why humans can
digest starch but not cellulose.
28. Objective
B.3.6
• Dietary fibre is mainly plant material
– Characteristics:
• Can’t be hydrolysed (digested) by enzymes in the human
digestive tract
• may be digested by microflora in the gut
• Examples:
– Cellulose
– Hemicellulose
– Lignin
– Pectin
State what is meant by the term
dietary fibre.
29. Objective
B.3.7
• Dietary fiber passes through the body without being
changed or digested much.
• Aids the health of the large intestine by stimulating the
production of mucous and helping the other products
of digestion to pass out of the body more easily.
• Foods that are high in fiber: bran, dried herbs, spices,
and peppers, soy beans, dark chocolate, and nuts.
• Prevents:
– Constipation
– Obesity
– Crohn's disease
– Hemorrhoids
– Diabetes mellitus
Describe the importance of a diet
high in dietary fiber.
Editor's Notes
Both are hexose sugars with molecular formula C6H12O6
1st carbon of one glucose is covalently bonded to the 4th carbon of the other glucose
Condensation can be repeated with disaccharides to form polysaccharides
Condensation can be repeated with disaccharides to form polysaccharides
