Carbohydrates
WJEC GCE BIOLOGY
Carbohydrates
2.6
2.6
Carbohydrates
Carbohydrates are made from CARBON,
HYDROGEN and OXYGEN
They STORE ENERGY in plants and animals
Plant cell walls depend on the structural role
of some carbohydrates
Carbohydrates
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CARBOHYDRATES
MONOSACCHARIDES
DISACCHARIDES
POLYSACCHARIDES
Monosaccharides
Monosaccharides are small organic molecules used as bulding blocks for more
complex carbohydrates. Click each of the blue boxes to work through the slide.
General Formula
(CH2O)n
Carbohydrates
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So, when
n=3
When n=5
What does the ‘n’ stand
for?
Number of Carbon atoms
TRIOSE, e.g. glyceraldehyde -
In metabolic reactions
When n=6
PENTOSE, e.g. ribose –
HEXOSE, e.g. glucose -
formation of nucleic acid
main source of energy
next
Isomerism in Glucose C6H12O6
Alpha-glucose
CH2OH
Oxygen
Hydrogen
Carbon
Hydroxide (OH)
beta-glucose
Carbohydrates
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CH2OH
Show structural change
Carbohydrates
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Optical Isomerism in Glucose
Optical Isomerism in Glucose
Carbohydrates
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Mirror
Disaccharides
Disaccharides form when two monosaccharide units join forming a
glycosidic bond, by a condensation reaction.
A disaccharide can be made
from two of the same
monosaccharide molecule or
from two different ones.
The combination of
monosaccharides determines
which disaccharide is formed.
Carbohydrates
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MONOSACCHARIDES
DISACCHARIDE
GLUCOSE
GLUCOSE
WATER
SUCROSE
MALTOSE
GALACTOSE
FRUCTOSE
GLUCOSE
LACTOSE
Forming Disaccharides
Glucose
CH2OH
CH2OH
CH2OH
H
C
OH
C
O
H
OH
H
C
C
H
OH
H
H
C
C
OH
OH
C
O
H
OH
H
C
C
C
H
OH
H
OH
Maltose
CH2OH
Carbohydrates
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H
C
OH
C
CH2OH
O
H
OH
H
C
C
H
OH
H
H
C
C
OH
OOH
H
H
Glycosidic
Bond
C
O
H
OH
H
C
C
C
H
OH
H
OH
This is a CONDENSATION
reaction, where a water
molecule is lost.
Polysaccharides
Polysaccharides are large complex molecules known as
POLYMERS.
What is
polymerisation ?
Carbohydrates
Polysaccharides
Polymerisation is the process of
bonding many MONOMERS by
condensation reactions to form one
large molecule.
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What is a
monomer?
Click the
bubble for
the answer
Monomers are the individual
monosaccharides which join
to form the polysaccharide.
Monomer
STARCH
CELLULOSE
GLYCOGEN
α Glucose
β Glucose
α Glucose
Return to isomerism of glucose
Glycosidic bond
1-4
1-4
1-6
Next
Carbohydrates
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Alpha vs Beta Glucose
Forming polysaccharides
Glucose
CH2OH
H
C
OH
C
CH2OH
O
H
OH
H
C
C
H
OH
H
H
C
OH
H
C
O
OH
H
C
CH2OH
O
H
OH
H
C
C
H
OH
H
H
C
OH
H
C
O
OH
H
C
CH2OH
O
H
OH
H
C
C
H
OH
H
H
C
OH
H
C
O
OH
H
C
O
H
OH
H
C
C
C
H
OH
H
Carbohydrates
WJEC GCE BIOLOGY
In this example, 3 condensation reactions have produced 3 water
molecules to produce the polysaccharide.
A HYDROLYSIS reaction (addition of water) reverses the reaction
and splits the polysaccharide releasing 3 monosaccharide
molecules.
OH
Carbohydrates
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You can give this
question a go, in
order to prove your
understanding:
You can give this
question a go, in
order to prove your
understanding:
Monomer
Maltose
Carbohydrates
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A water molecule
C1 and C4
These two forms of glucose are (stereo)isomers, because they contain the
same atoms, but they differ in the arrangement of their atoms in space
Beta glucose