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BIOCHEMISTRY
© 2007 Paul Billiet ODWS
CARBON
Tetravalent  4 different bonds  variety
 isomerism
 Forms long chains (polymers) 
macromolecules and ring structures
 Tetrahedral structure  3-D variation 
optical isomerism
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© 2007 Paul Billiet ODWS
Organic compounds
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Compounds containing carbon found in living
organisms
Not including carbonates, hydrogen carbonates,
CO2 or CO
Often based upon a skeleton of carbon
An infinite variety possible
Evolution has chosen a few for use in living
organisms
There are four principal groups: sugars, fatty
acids, amino acids and nucleotides
© 2007 Paul Billiet ODWS
CARBOHYDRATES (CH2O)n
Organization: Monosaccharides,
Disaccharides, Polysaccharides
Monosaccharides
 5C pentoses (eg ribose, deoxyribose)
 6C hexoses (eg glucose, fructose, galactose)
CH2OH
O
H
C
C
H
CH2OH
OH
H
H
C
C
OH
OH
© 2007 Paul Billiet ODWS
C
H
RIBOSE
GLUCOSE
C
O
H
OH
H
C
C
H
OH
OH
H
C
OH
Glycoside linkage to form
disaccharides
The two sugars are joined by condensation
and may be broken by hydrolysis
CH2OH
CH2OH
H
C
C
H
OH
H
C
C
H
OH
OH
© 2007 Paul Billiet ODWS
O
H
H
C
O
C
C
H
OH
H
C
C
H
OH
OH
OH
H
C
OH
A disaccharide
CH2OH
CH2OH
H
C
C
H
OH
H
C
H
OH
H
H
C
O
C
C
H
OH
H
C
C
C
OH
H
OH
O
O
+ H2O
© 2007 Paul Billiet ODWS
H
C
OH
Different monosaccharides can
be used
sucrose = glucose + fructose
 lactose = glucose + galactose
 maltose = glucose + glucose
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© 2007 Paul Billiet ODWS
Polysaccharides
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Macromolecules
Common ones based upon glucose
Branched polysaccharides
 Amylose & amylopectin (starches) are
synthesised in plants.
 Glycogen is synthesised in animals, more
highly branched than starches = more compact
Unbranched polysaccharides
 Cellulose in plant cell walls
© 2007 Paul Billiet ODWS
CARBOHYDRATE FUNCTIONS
Sugars (mono and disaccharides) small molecules
soluble in water:
 Maintenance of osmotic balance (e.g. salts in blood
plasma, plant cell turgidity);
 transport of energy reserves (e.g. glucose in blood or
sucrose in sap);
 energy substrate (respiration and photosynthesis);
 energy store (sugar cane);
 flavouring (fruits); reward (nectar);
 precursors (building blocks) of polysaccharides,
nucleotides and amino acids
© 2007 Paul Billiet ODWS
CARBOHYDRATE FUNCTIONS
Polysaccharides Large molecules
insoluble in water:
 Osmotically inactive carbohydrate storage,
(seeds, roots, chloroplasts);
 Structural (cellulose in plants)
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© 2007 Paul Billiet ODWS
LIPIDS C, H, O
More hydrogen (more reduced) than
carbohydrates.
 Insoluble in water, soluble in organic
solvents (alcohols, acetone, chloroform
etc)
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© 2007 Paul Billiet ODWS
Fatty acids: carboxylic acid + long
hydrocarbon chain
A saturated fatty acid
Carboxylic acid
O
CH3
Hydrocarbon chain
C
OH
An unsaturated fatty acid
O
CH3
C
OH
© 2007 Paul Billiet ODWS
Saturated fatty acids
Unsaturated fatty acids
no double bonds
one or more double bonds
abundant in fats
abundant in oils
more reduced
less reduced
more energy
less energy
high melting point
low melting point
© 2007 Paul Billiet ODWS
Fats and Oils
fatty acids + glycerol (1, 2 or 3 = mono , di
or triglycerides)
O
CH
C
OH HO - CH2
O
3
CH
3
C
OH HO - CH
HO – CH2
© 2007 Paul Billiet ODWS
Condensation
reactions
Two fatty acids joining glycerol
= A diglyceride
O
CH3
C
O - CH3
O
CH3
C
O - CH
HO - CH3
© 2007 Paul Billiet ODWS
+
2H20
Phospholipids
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in lipoprotein membranes (plasma,
nuclear, mitochondrial etc.)
© 2007 Paul Billiet ODWS
Other lipids
Steroids: multiple ring structures (e.g. cholesterol)
 Functions: cell membrane structure, digestion
(help to emulsify fats), hormones (testosterone
etc), vitamins (e.g. Vitamin D), poisons
Waxes: long chain alcohol + fatty acids
 Water proof coating to leaves, fur feathers,
insect exoskeletons.
 Used by bees to construct their honey combs.
© 2007 Paul Billiet ODWS
LIPID FUNCTIONS IN GENERAL
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STRUCTURAL: biological membranes (phospholipids,
steroids, glycolipids), cushioning (fat deposits round the
kidneys)
ELECTRICAL INSULATION: myelin sheath round axons
THERMAL INSULATION: subcutaneous fat deposits.
WATER PROOFING: waxes and oils
ENERGY STORE AND SUBSTRATE: very condensed
form of energy (37 kJ g-1) used by animals and seeds.
HORMONES: steroids
VITAMINS: precursor to Vit D
BUOYANCY: oil droplets in plankton
© 2007 Paul Billiet ODWS
AMINO ACIDS & PROTEINS: C, H, O, N, S
cysteine
arginine
methionine
phenylalaline
aspartic acid
© 2007 Paul Billiet ODWS
Amino acids

amino group, carboxyl group,
hydrogen and a variable side group
(residue) each joined to a central carbon
atom
R
H2N-C-COOH
H
© 2007 Paul Billiet ODWS
Types of amino acids
Amino end and carboxyl end can be
ionised NH3+ and COO- to give acidic and
basic characteristics
 At pH 7 both groups are ionised.
 The residues are side chains which give
the individual properties to the amino acid
(acidic, basic, neutral and nonpolar)
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© 2007 Paul Billiet ODWS
Functions of amino acids
Protein synthesis, energy reserve,
hormones (thyroxin)
 20 different amino acids used in protein
synthesis though others do occur in
nature.
 Essential amino acids cannot be
synthesised by the organism and must
form part of their diet
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© 2007 Paul Billiet ODWS
The peptide bond
Carboxyl group + amino group form a
strong covalent bond releasing water in to
process water = a condensation reaction
(the reverse is hydrolysis)
 Amino acids join together in a long chain:
N terminal end to C terminal end = a
polypeptide
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© 2007 Paul Billiet ODWS
H
N
H
R
O
C
C-OH
H
N
H
R
O
C
C-OH
H
H
Condensation
reaction
A dipeptide is formed
H
N
H
R
O H
R
O
C
C N
C
C-OH
H
H
The peptide bond
© 2007 Paul Billiet ODWS
+ H2O