All B3 Objectives
B.3.1: Describe the structural features of monosaccharides.
B.3.2: Draw the straight-chain and ring structural formulas of
glucose and fructose.
B.3.3: Describe the condensation of monosaccharides to form
disaccharides and polysaccharides.
B.3.4: List the major functions of carbohydrates in the human
body.
B.3.5: Compare the structural properties of starch and
cellulose, and explain why humans can digest starch but
not cellulose.
B.3.6: State what is meant by the term dietary fibre.
B.3.7: Describe the importance of a diet high in dietary fibre.
Objective
B.3.1
Describe the structural features of
monosaccharides
• 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
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.3.2
Draw the straight-chain and
ring structural formulas of glucose
and fructose
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
Objective
B.3.2
Draw the straight-chain and
ring structural formulas of glucose
and fructose
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
The ring-structure forms when
glucose is dissolved in water
and undergoes and internal
reaction
Objective
B.3.2
Draw the straight-chain and
ring structural formulas of glucose
and fructose
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
Fructose: Straight-Chain
Formula
• 6-carbon backbone
• Carbon 1 and Carbon 6 both
O
H
have two hydrogens and 1
C
hydroxide
H C OH
• Carbon 2 has one single
HO C H
Oxygen
H C OH
• Carbons 3, 4, and 5 all have H C OH
one hydrogen, one hydroxide
CH2OH
– Carbon 3 is flipped
glucose
(hydroxide on the left)
O
CH2OH
C
HO C H
H C OH
H C OH
CH2OH
fructose
Objective
B.3.2
Draw the straight-chain and
ring structural formulas of glucose
and fructose
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
The ring-structure forms when
hydrogens and one
fructose is dissolved in water
and undergoes and internal
hydroxide
reaction
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.
Objective
B.3.3
Describe the condensation of
monosaccharides to form
disaccharides and polysaccharides.
• 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
– 14 linkage utilizing covalent bond (glycosidic bond)
Objective
B.3.3
Describe the condensation of
monosaccharides to form
disaccharides and polysaccharides.
H
H
glucose
glucose
+ H2O
maltose
Objective
B.3.3
Describe the condensation of
monosaccharides to form
disaccharides and polysaccharides.
• Monosaccharide examples:
– Glucose, Fructose, Galactose
• Disaccharide examples:
– Lactose, Maltose, Sucrose
• Polysaccharide examples:
– Starch, Glycogen, Cellulose
Objective
B.3.3
Describe the condensation of
monosaccharides to form
disaccharides and polysaccharides.
• Disaccharide Structures:
– Lactose (in milk)
• 1 beta-glucose + 1 beta-galactose
– Maltose (starch digestion product)
• 2 alpha-glucose
– Sucrose (canesugar, common in food)
• 1 alpha-glucose + 1 beta-fructose
Sucrose
Objective
B.3.4
List the major functions of
carbohydrates in the human body
• Major functions:
–Energy Source
–Energy Storage
–Important for Other Molecules
Objective
B.3.4
List the major functions of
carbohydrates in the human body
• 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
http://www.individualsole.com/wp-content/uploads/2010/05/SpSu10_Running_02035_ipod-540x360.jpg
Objective
B.3.4
List the major functions of
carbohydrates in the human body
http://drpinna.com/wp-content/uploads/2010/08/glucose.gif
Objective
B.3.4
List the major functions of
carbohydrates in the human body
• 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
http://findstorageauctionriches.com/IMAGES/self-storage-units.jpg
Objective
B.3.4
List the major functions of
carbohydrates in the human body
http://themedicalbiochemistrypage.org/images/glycogen.jpg
Objective
B.3.4
List the major functions of
carbohydrates in the human body
• 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)
Ascorbic Acid (Vitamin C)
http://upload.wikimedia.org/wikipedia/commons/8/81/Ascorbic_acid_structure.png
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
Objective
B.3.5
Compare the structural properties of starch
and cellulose, and explain why humans can
digest starch but not cellulose.
– 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.
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.
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.3.6
State what is meant by the term
dietary fibre.
• 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
Objective
B.3.7
Describe the importance of a diet
high in dietary fiber.
• 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
References
• http://www.elmhurst.edu/~chm/vchembook/540carbohy
drates.html
• http://ibchem.com/IB/ibnotes/brief/pdf/optB.pdf
• http://www.chem.purdue.edu/courses/chm333/Fall%202
009/Lectures/Fall%202009%20Lecture%2028.pdf
• http://www.mansfield.ohiostate.edu/~sabedon/biol1025.htm
• http://www.3dchem.com/molecules.asp?ID=423
• http://www.edinformatics.com/math_science/science_of
_cooking/glucose.htm
• http://www.elmhurst.edu/~chm/vchembook/547cellulos
e.html