Download Carbohydrate Structure

Biological Molecules
Sugars, polysaccharides, lipids and fats
by Athene Donald
Slide 1: Carbohydrates and lipids each represent an enormous family of
molecules with some common characteristics. However, small and subtle
differences in the placement of an additional group can make a vast difference to
their biological properties. (Copyright Athene Donald.)
3a (left) Linear form and Fischer projection in
which the two side groups at C1 are reversed.
2b (above) Haworth projection showing the
two isomers of D-glucopyranose.
Slide 2: Basic carbohydrate structure. (From Coultate T.P. 1999 Food: the
Chemistry of its Components, 2nd edn, Springer, reproduced by permission of the
Royal Society of Chemistry.)
lactose
sucrose
Slide 3: Disaccharides. (From Coultate T.P. 1999 Food: the Chemistry of its
Components, 2nd edn, Springer, reproduced by permission of the Royal Society
of Chemistry.)
Slide 4: Polysaccharides. (From Coultate T.P. 1999 Food: the Chemistry of its
Components, 2nd edn, Springer, reproduced by permission of the Royal Society
of Chemistry.)
Slide 5: Cellulose and starch.
The helical packing through the wall thickness leads to arcs being seen
in cross-sectional images (e.g. in the transmission electron microscopy).
Slide 6: Helical packing in the plant cell wall. (From Neville, A.C.1993 Biology of
Fibrous Composites Cambridge University Press, reproduced by permission of
Cambridge University Press.)
• C6H12O6 + 6O2  6CO2 +6H2O aerobic conditions
DG = –2881 kJ/mol
• Anaerobic respiration (respiration when oxygen supply is
limited) proceeds via glycolysis, in which glucose is broken
down to pyruvate in a series of stages involving ATP
(discussed elsewhere).
• In plants, the end-product in this process of anaerobic
respiration is alcohol, while in many animal cells and bacteria
the end-product is lactate.
Slide 7: Glucose metabolism.
• This is a hierarchical model.
• One can see how different architectures and compositions of the constituent
molecules may affect the details of the packing.
• The amylopectin molecules are aligned radially.
Slide 8: Model for the starch granule.
Schematic of the structure of the
collagen triple helix.
Crosslink formation between
collagen chains. Crosslinking
increases with age, causing
skin to lose elasticity, for
instance.
Slide 9: Collagen. (Left-hand image from Ross-Murphy S.B. (ed) 1994 Physical
Techniques for the Study of Food Biopolymers, chapter 3 Blackie Academic,
Alan Clarke Figure 23, reproduced with permission of Springer Science +
Business Media B.V. Right-hand image from Coultate T.P. 1999 Food: the
Chemistry of its Components, 2nd edn, Springer, Figure 5.11 reproduced by
permission of the Royal Society of Chemistry.)
Slide 10: Structures of fats and lipids.
UNSATURATED
Oleic CH3(CH2)7CH=CH(CH2)7COOH
Linoleic CH3(CH2)4(CH=CHCH2)2(CH2)6COOH
Linolenic CH3CH2(CH=CHCH2)3(CH2)6COOH
Arachidonic CH3(CH2)4(CH=CHCH2)4(CH2)2COOH
Slide 11: Examples of fatty acids.
SATURATED
Lauric CH3(CH2)10COOH
Palmitic CH3(CH2)14COOH
Stearic CH3(CH2)16COOH
Triglycerides are formed by the
addition of three fatty acid
chains to glycerol.
Slide 12: Triglycerides.
The fatty acid chains can be
wholly saturated or can
contain some unsaturated
chains, thereby introducing
kinks into the tails.