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BIOCHEMISTRY
The study of chemical constituents of living organisms.
Organic Molecules - Materials that are formed in the metabolism of living things.
The wide range of Organic compounds in living organisms may be conventionally divided into 5 major
groups:
1
Carbohydrates
2
Lipids (Fats)
3
Amino Acids and Proteins
4
Nucleotides and Nucleic Acids
5
Group of complex organic molecules including Porphyrins (eg Haemaglobin, Chlorophyll)
CARBOHYDRATES
Defn: Containing Carbon, Hydrogen and Oxygen. Where the ration of H : O is 2 : 1 as in H2O (water)
General Formula
CnH2nOn or C(h2O)n where n = whole No
There are a few exceptions eg Pentose (5C) sugars in DNA has a molecular formula C 5H10O4, also Chitin
has N as well as C,H,O.
Simple classification of C/H
Mono
Simple
Oligo (mainly Di)
Saccharides
(Sugar)
Carbohydrates
Poly
Complex ------ Carbohydrate derivatives eg Chitin, Pectic Acid
Biological Importance
1
2
Energy Source
Carbohydrates are principal respiratory substrates
Structural Compounds
eg Cellulose (CW of all plant cells)
Lignin
3
Storage Compounds
eg 1. Starch
(common plant storage never in animals)
Plants
2. Sucrose ( eg sugar cane, sugar beet)
3. Inulin
Animals - 4. Glycogen (eg mammalian liver
4
Glycoside Formation Wide variety of compounds/ functions eg colouration in flowers (see later )
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CLASSIFICATION
The basic sugar unit = the saccharide . The group is classified according to the No of units
1 sugar unit
2 sugar units
Many sugar units
=
=
=
Monosaccaride
Disaccharide
Polysaccharide
NB The Di and Tri saccharides are also called Oligosaccharides. DES (Oligo = ‘Few’)
Nomenclature (naming C/H) - commonly used is the suffix (ending) OSE to indicate a C/H ie:
Gulcose
Cellulose
Fructose
etc
C/H in more detail…….
A
Monosaccharides
General
There are the building blocks of other important C/H’s n in the general formula is 2-8. All
monosaccharides are:
a
b
c
d
e
Nomenclature
Sweet tasting
Soluble in water
Form crystals
Reducing sugars (see below)
Are subdivide according to C atom No
3C atom M/S = Triose sugars (occur in resp. glycolysis)
4C atom M/S = Tetrose sugars (photosynthesis)
5C atom M/S = Pentose sugars
6C atom M/S = Hexose sugars
7C atom M/S = Heptose suagars
Chemical Nature
Aldose sugars ~ process ALDEHYDE gp. (-CHO)
Monosaccharides
are either
Ketose sugars ~ process KETO gp. (-C=O)
These chemical groups affect fundamentally the Chemical properties of a C/H
eg
Aldose M/S = glucose
Ketose M/S = fructose
Reducing Sugar Properties (all M/S are reducing sugars). Both Aldose anmd Ketose M/S are capable of
REDUCING Cu III (Cuprous)  Cu II (Cuprous) in HOT, ALKALINE solution. When this reduction
occurs as Cu II is insoluble it PRECIPITATES  Brick Red/Orange Red ppt.
NB
Benedicts Solution - Alkaline solution of Copper Acetate (Fehling solution also produces
similar results)
NOTE
Polymerised C/H’s have a free -OH (Hydroxyl group) and -H group on C, to be reducing
sugars
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General Chemical Test for all C/H = Barfoeds test (see separate note practical file.
HEXOSE MONOSACCHARRIDES
Here n = 6  subs in general formula C6 H12 O6 = molecular formula
Structural Isomeration
There are however a number of different ways of arranging molecules (configurations) for C 6H12O6 ie 2
different structural versions of C6H12O6 are:
Fischer projections
CHO
CHO
HO
OH
HO
HO
HO
OH
OH
OH
CH2OH
CH2OH
2 More common sugars are:
CHO
OH
2
HO
CH2OH
=O
HO
3
4
OH
OH
5
OH
OH
OH2OH
(Aldose sugar) glucose
OH2OH
(Ketose sugar) fructose
The carbon atoms C2 C3 C4 C5 with 4 different groups attached are called asymetric carbon atoms allowing
24 different just 6 common.
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Stereo - Isomerism
As with structural isomerism  of the presence of asymmetric C atoms it is possible to have chemical
groups attached to the 4 central C atoms in different positions so that minor images result.
This is
 -D- glucose ( 
form is called TRANS form)
This is

-D-glucose (  form is called CIS form)
The  &  form is fundamentally important when the sugars enter into combination with other sugars
(polymerisation) to form molecules like starch and cellulose.
Polymerisation of
 - D - glucose
Polymerisation of  -D- glucose  starch
 cellulose
NOTE THE 5C RING FORM
= The PYRANOSE Ring
GLYCOSIDE FORMATION
A very important monosaccharide characteristic is the ability to form compounds called glycosides where
the OH group attached to 1C reacts with other groups (radicals or molecules) eg1 Phosphate Group 
Sugar Phosphates.
In more detail…..
1
Sugar Phosphates (Phosphate = PO2-4)
*
Glucose-1-phosphate is important in respiration see later.
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P = Phosphate
14
Other glycoside include:
a
b
Coloured compounds like ANTHOCYANINS ie RED  PURPLE compound eg beetroot juice.
ANTHOXANTHINS ie YELLOW CREAM eg Daffodil Petals.
Toxic compounds (plant protection compounds - natural anti fungicide eg Cyanophoric* glycosides
in cherry laurel, hawthorn (* give off -H HCN) Saponin glycoside eg digitalin (foxgloves).
Summary: Glycosides are
a
A protective, reducing herbivore attack and fungal attack - toxic glycosides
b
Play important part in pollination, coloured petals etc
c
Play an important part in dispersal, coloured trunks etc
2
Oligosaccharides
These include C-H’s which on hydrolysis yields a small No of saccharide units ie 2,3 or 4 sugar units.
a
Disaccharides These are a form of glycoside. The general
formulae is (CnH2nO+CnH2nOn) - H2O
*
Glycoside Nature
All Disaccharides are a form of glycoside as the 2nd sugar unit attaches (by
the OH group of sugar unit 1. see below:
Examples of D/S
1
Maltose (Malt sugar)
2
Cellobiose (not naturally occuring but the “monomer” of cellulose
3
Sucrose (cane sugar)
4
Lactose (milk sugar)
1
Maltose
Molecular formula C12H22O11 (ie n= 6 in the general formula)
formation - formed by CONDENSATION of 2 units of  -D-glucose
Linkage is 1:4
Eqn:
Hydrosis of Maltose
1
By boiling in solution (v.slow)
2
By boiling with dil HC1 (fairly rapid)
3
Enzymatic hydrosis via maltose (fastest)
NB
Maltose is usually synthesised by hydrolysis of starch
General Properties
1
Free OH and -H group attached to 1C  REDUCING SUGAR
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condensation) to
2
3
Maltose is the repeating unit (MONOMER) of Starch
Maltose (Milk Sugar) is produced in the “Malting” stage of brewing (1st step)
2
Sucrose
Molecular formula C12H22O11
Formation - formed by CONDENSATION of
phosphate)
Lineage
 -D-fructose and  -D-glucose (usually as a sugar
1:2
Eqn
Synthesis In PLANTS only. Made form glucose 1-P (glycoside) + fructose via enzyme SUCROSE
PHOSPHORYLASE.
Hydrolysis of Sucrose
1
2
Boil in solution with dil HC1 (fairly rapid)
Enzymatic hydrolysis via SUCRASE
General Properties
1
NON-REDUCING sugar ie no free OH and -H group on 1C
2
Important as (a) Main TRANSLOCATE in the phloem of higher plants (b)
carbohydrate in sugar beet and sugar cane.
3
Cellobiose
Molecular formulae C12H22O11
Formation -
Formed by CONDENSATION of
Lineage
1:4
 -D-glucose
Eqn
Hydrosis of Cellobiose
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storage
1
2
Hot acid (very slow)
Enzymatic (cytase)
General Properties
1
2
3
Reducing sugar
Monomer - repeating units of cellulose
Does not occur naturally as the free sugar
4
LACTOSE
Molecular formulae C12H22 O11
Formation
- by CONDENSATION of 1 unit of
1 unit of  -D-glucose
Lineage
1:4
 -D galactose and
Eqn
Hydrolysis
1
2
Hot acid (very rapid)
Enzymatic
General Properties
1
2
REDUCING SUGAR
Forms 6% by dry weight of human milk
General Summary
1
2
3
4
May be reducing or non-reducing
Sweet tasting
Water soluble
Form crystals
POLYSACCHARIDES
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General Introduction
These are an important group of carbohydrates. Two main divisions:
a
b
Structural Polysaccharides eg Cellulose, Chitin, Lignin (wood)
Storage Polysaccharides eg Starch, Glycogen and Insulin
General Formula
(CnHzn-2 On-1)x
Where n = 4-6
x = 100’s (sometimes 1000’s)
Genral Properties of P/S
Sugar properties lost all are:
1
2
3
Non sweet tasting
Non truly soluble in H2O (form collodial sols not crystaloid sols)
Non Cyrstaline
Structural P/S
In these polysaccharides the sugar unit residues present in the  form the long chain molecules of the
polymer are straight, and cross-linkages between chains occur giving the material its strength.
A Cellulose
From general formula n=6 (C6H10O5) 100’s
Formation
the monomer is cellabiose which condense together in a 1:4 linkage.
Representation of a portion of celluboise molecule:
MACROSTRUCTURE
Each cellulose chain is thought to be at least 500 celluboise residues long and can be up to 5000.
H-bonding occurs between chains due to projecting OH groups forming a 3D lattice called a microfibril.
The long chain polymers of cellulose, may X-link due to H bonding between projecting -OH groups
creating a 3D lattice arrangement which has considerable mechanical strength, the lattice arrangement
creates a ‘bundle’ of cellulose polymers which is called a Microfibril.
In the primary and secondary cell walls of higher plants ,highly visible under the EM (usually heavy metal
shadowed), are the Microfibrils, often arranged with bundles of microfibrils = MICROFIBRILS (Ref see
handout - Cytology)
Diagram of a Microfibril of Cellulose
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Commercial Importance of Cellulose
See Roberts p68 (Old Roberts)
Synthesis
2 enzymes involved
 -D glucose
Cellobiose
Cytose
Cellobiose
Cellulose
Photosynthesis (or from storage P/S)
Hydrolysis
1
2
Hot acid hydrolysis (very slow)
Enzymatic enzyme cellulose
Cellulose
 ,D - glucose and F
NB
Cellulose is exclusive to the invertabrates (ie No Vertabrate makes cellulose) only larhe
invertabrates = snail (in UK) eg Cellulose secreted by protazoan Trichonympha found in the gut of termites.
Relation of trichonympha found in the gut of RUMINANTS (animals with Rumen - which acts as a
fermentation chamber in the gut)
Test for Cellulose
Zinc-chlor-iodide solution (SHULTZES SOLUTION) deep blue colour = the result
Hemicellulose
A mixed bag. Hemicelluloses are present in the Primary and Scenondary cell walls of the plants they fill in
the spaces between the cellulose microfibrils and the macrofibrils.
H Celluloses are polymers of (usually  -D) sugars, OTHER than glucose eg PENTOSE (5C) sugars
including - Xylose, Arabinose
HEXOSE (6C) sugars including - Galactose, Mannose
Hemicellulose molecules unlike cellulose may be branched.
Structural Carbohydrate - Derivatives
A derivative in this case is a molecule that has some C/H qualities but is not a C/H.
a
PECTIC COMPOUNDS
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Consist of Polymers of Sugar-acids, most common sugar acid is PECTIC ACID = a polymer of  D-galacturanic acid.
The Carboxyl (-COOH) or acid groups of pectic acid combine readily to form salts with divalent ions like
Ca2+ or Mg2+ - The Ca/Mg acting as X-links between polymers  very strong adhesive substances. Ca/Mg
Pectates = the substance of the middle lamalla in plant cells.
Diagram of Ca/Mg Pectate
b
CHITIN
Located in the exoskeletons of anthropods found in the cell walls of some fungi. Chitin is a
polymer of acetyl glucosmine - this is the acetyl derivative of the N containing amino-sugar
glucosamine. The linkages between monomers is 1:4
Lignin Tests
Chemical Test:
Macroscopic - acidified phloroglucinol  red colour indicates lignin.
Microscopic - amiline chloride/sulphate  yellow colour
indicates lignin.
c
LIGNIN (wood)
Closely related to the C/H’s but strictly speaking not a C/H.
Lignin is the chemical term for wood - the principal strengthening material for the Zudary
cell wall in plant material. Lignin is a 3D polymer made up of Phenyl Propane residues.
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Occurance lignified plant tissue are :
a
b
Xylem vessels
Fibre cells eg sclerenchyma
collenchyma
Food Storage in C/H
In these polymers the sugar monomers are assembled in the alpha configuration. The linkages,
principally 1-4 are all on thje same side of chains, the chains are  not straight.
a
Starch
Molecular formula (C6H10O5)x where x = 300-1000
There mare two natural forms of starch 1 is Amylose starch (35% of starch is soluble) the other is
Amylopectin Starch.
Occurance:
1
1
2
3
Pea seeds = 100% Amylose Starch
Maize Seeds = 100% Amylopectin Starch
Most plants = mixture of both
Amylose (soluble starch)
Structure: This is a HELICALLY coited molecule which is made up of unbranched chain
of 300-1000  -D-glucose residues the linkage is 1:4 (sometimes the odd  -D-glucose
residue is present)
Representation of Amylose Molecule
The average Mr is approx 60,000
Chemical test for amylose:
Reagent = Iodine (I2) Potassium Iodide (KI) solution - deep blue/black colouration
amylose. + due to starch iodine complex.
Note: 1
2
3
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Amylose + water  Colloidal sol
Ideal storage/food reserve
a
b
c
d
AMYLOPECTIN
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+
indicates
No interference with cell
Insoluble
metabolism
Low OP
HEC (high energy compound)
Large molecules (can’t escape)
Structure
This is a 2D branched chain of  -D-glucose residues.
Linkages are 1:4 & 1:6.
Representation of Amylopectin molecule:
Starch Synthesis
Starch phosphorylase
glucose - 1 - P
Starch + X P1
(glycoside)
Starch Hydrolysis
Amylose - A
Amylopectin -B
1
2
3
A  Shorter chains  Maltose
B  Shorter chains (dextrins)
Boil A/B with oil HCI  dextrins  Maltose  glucose
Heating to 2000C
Enzymatic hydrolysis
In animals -2 step process:
Step One
Salivery AMYLASE Pancreatic AMYLASE
Amylase
Starch
(1 or 2)
Step Two
Maltose
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Maltose
Maltase (in pancreatic juice)
Glucose (  -D)
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In plants - enzyme complex - = DIASTASE completly hydrolyses starch
DIASTASE contains following enzymes
Amylase

Amylase

R
Enzyme
Maltase
 ) Amylase then Maltase in Diastase to
 -D-glucose (may be small amount of  -D glucose)
Hydrolysed by  (&
AMYLOSE
AMYLOPECTIN
Location of Starch
Found as granules in a large variety of plant cells in all parts of the plant but especially the:
a
b
c
Roots - Parenchuma cells of CORTEX
Endodermis (tissue) = Starch sheath in both roots & stems
Leaves - Mesophyll cells
More detailed location in plant cells:
1
2
3
Lencoplants = membrane bond organelles in starch
Chloroplants
Pyrenoids
Detail of starch grain
Rice Starch
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Potato
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Wheat
b
GLYCOGEN (Animal Starh)
Molecular Formula (C6H10O5)n where n = whole No  100’s
General
Glycogen is a polymer consisting of many  D glucose residues linked together 1:4 with branches via 1:6
linkages, the polymer is 2D resembling Amylopectin - principal difference is that the branches are 2x as
numerous. Each chain length is 18  -D-glucose residues long.
representation of glycogen
Function
Glycogen is the main storage C/H in animals.
Location in Mammals
1
2
3
Liver Cells (hepatocytes)
Muscle Cells
Brain Cells
Hormonal role in Homeostatic blood sugar regulation:
Insulin  cells of islets*
Glucose
Glycogen
(in liver cells)
Glucagon  cells if islets
(in solution in
blood plasma)
* Cells of the islets of Langerthan in the pancreas.
c
INULIN
This storage C/H is common in a group of plants known as the Compostae which includes: Dandelion,
Sunflower, Dalia and Artichokes.
General
The monomer is  -D-fructose linkages are 1:2 and a glucose residue is usually found at the end of the
chains which are straight and unbranched.
Representation of Inlulin Molecule
Note: Never found in animals
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