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GCSE level organic chemistry exam
revision notes: Part
11C.
Comparing
natural polymers including proteins, DNA,
wood, silk, starch, cellulose
(key
revision points at the end of the page)
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Dr Phil Brown PhD:
Doc Brown's chemistry exam revision notes on
oil products &
organic chemistry - comparing types of polymers,
suitable for students of UK GCSE Science level
AQA, Edexcel, OCR, WJEC and CCEA GCSE chemistry
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[page updated Mar 16th 2026 *]
Sub-index extra
section son polymers
11A
Comparing
themoplastics, thermosets and fibres
11B
Synthetic
condensation polymers like Nylon and Terylene - basic structure, properties and
uses
11C.
Examples of natural polymers, their structure, function and uses
e.g. starch, proteins, DNA
(this page)
11D.
An exercise in choosing a plastic for a particular
use
INDEX of ALL my synthetic polymer-plastic pages revision notes
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GCSE level m/c QUIZ on oil products & organic chemistry
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11C. Examples of
NATURAL POLYMERS,
their structure, function and uses
Overlaps with Part 12
(re-think?)
- Note that silk and cotton fibres (strong
fibres for fabrics), rubber (for tyres and elastic objects) are very
useful natural materials that have been harvested for many years from
the natural world.
-
Silk has been used as a
clothing and decorative fabric for thousands of years, and, like sheep's
wool, is essentially a protein polymer material.
-
Rubber has been used for
centuries as a natural elastic polymer, but it has been replaced by
synthetic polymers like neoprene.
-
Wood is an extremely useful construction
material, and is mainly a polymer mixture of cellulose (a natural polymer of
glucose) and lignin (with a strong rigid cross-linked polymer structure
giving wood more strength and hardness).
- The valuable crop of
cotton (for
fabrics) also has a molecular structure based on cellulose, in fact it is
the purest form of cellulose that occurs naturally and forms strong
useful fibres.
-
Starch,
cellulose and sugars are all carbohydrate
molecules
- Sugars are small molecules, but starch and
cellulose are natural
condensation polymers of sugars based on the condensation
polymerisation of small sugar molecules like glucose.
- Starch and sugars are used in the food industry,
starch being a polymer based on sugar.
- See
also
Natural molecules - carbohydrates
- sugars - starch, DNA for more details
-
Amino acids have two functional groups from
which peptides and proteins are made.
- This involves a condensation polymerisation in
the biochemistry of living systems.
- The carboxylic acid group -COOH and
the amino or amine group -NH2
- The simplest one is aminoethanoic acid (glycine)
H2N-CH2-COOH
- Proteins are naturally occurring polymers
based on amino acids.
- Amino acids can undergo condensation
polymerisation via the two functional groups to form peptides,
and all sorts of combinations of amino acids produce the huge variety of
proteins found in living systems.
-
 For glycine the condensation polymerisation to
give a glycine peptide can be shown as ..
- n H2N-CH2-COOH
===> -(NH-CH2-COO-)n- + 2n H2O
- where n is a very large number, with the
elimination of 2n water molecules, one from each link at either end of
the glycine monomer molecule.
- The equation illustrates the structure if only
one amino acid is used, in reality, proteins are very complex using a
variety of around 20 different amino acids, each with its own unique
structure, leading to lots of different proteins with their own unique
structure. Think of all the different tissues in your own body!
- For more details see
Amino acids,
proteins, polypeptides, enzymes and chromatography for more
details.
-
DNA (deoxyribonucleic acid)
- DNA is a very large molecule essential for life
and the basis of genetic chemistry in living systems.
- In a cells biochemistry the DNA encodes genetic
instructions for the development and functioning of all living organisms
and viruses.
- Most DNA molecules are two polymer chains made
from four different monomers called nucleotides.
- Two strands of the DNA molecule are coiled
together in the form of a double helix.
- For more details see
DNA and RNA structure and Protein Synthesis gcse
biology revision notes
See also
A survey of the properties and
uses of a wide range of materials
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QUIZ on oil products & organic chemistry
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Key revision points
Summary
revision notes comparing natural polymers (silk, rubber, wood, cotton,
starch, cellulose, proteins, DNA) aligned with GCSE/IGCSE chemistry
specifications across AQA, Edexcel, OCR, WJEC, CCEA, and CIE.
What are Natural
Polymers?
- Definition:
Large molecules made of repeating monomers joined by covalent bonds.
- Formation:
Often via condensation polymerisation (loss of small
molecules like water).
- Examples:
Proteins, DNA, starch, cellulose, silk, rubber, cotton, wood.
Sources:
Comparative Table
of Natural Polymers
| Polymer |
Monomer Units |
Key Bonds/Structure |
Properties |
Uses |
| Silk |
Amino acids (protein) |
Peptide bonds, β-sheets |
Strong, flexible, lustrous |
Textiles, medical sutures |
| Rubber |
Isoprene units |
C=C bonds, cross-linked |
Elastic, waterproof |
Tyres, elastic bands |
| Wood |
Cellulose + lignin |
β-glucose chains + aromatic lignin |
Strong, rigid |
Construction, furniture |
| Cotton |
Cellulose (β-glucose) |
Long chains, hydrogen bonding |
Soft, absorbent |
Clothing, textiles |
| Starch |
α-glucose |
Amylose (helix), amylopectin
(branched) |
Insoluble, energy storage |
Food, biodegradable plastics |
| Cellulose |
β-glucose |
Straight chains, hydrogen bonds |
Strong fibres, insoluble |
Paper, textiles |
| Proteins |
Amino acids |
Peptide bonds, folding (α-helix,
β-sheet) |
Diverse functions |
Enzymes, structural tissues |
| DNA |
Nucleotides (A,T,C,G) |
Sugar-phosphate backbone, H-bonds |
Double helix, stores info |
Genetic material |
Key
Revision Points (Exam-Spec Aligned)
- Polymerisation types:
- Addition polymerisation:
synthetic polymers (polyethene).
- Condensation polymerisation:
natural polymers (proteins, DNA, starch, cellulose).
- Bonding:
- Proteins/DNA → peptide bonds &
hydrogen bonds.
- Carbohydrates → glycosidic bonds.
- Rubber → unsaturated C=C bonds allow
cross-linking.
- Structure → Properties → Uses:
- Silk:
ordered protein chains → strength & flexibility.
- Rubber:
flexible chains → elasticity.
- Cellulose:
hydrogen bonding → rigidity.
- DNA:
complementary base pairing → information storage.
- Environmental aspect:
Natural polymers are biodegradable, unlike many synthetic polymers.
Student Tips
- Link structure to use:
Always explain why a polymer’s structure makes it suitable for its
use (e.g., cellulose’s hydrogen bonding → strong fibres → paper).
- Compare natural versus synthetic:
Exams often ask to contrast biodegradability, bonding, and polymerisation
type.
- Use diagrams:
Draw simplified repeating units (e.g., glucose in starch versus cellulose).
- Terminology precision:
Know the difference between monomer, repeat unit,
polymerisation type.
Common
Misconceptions
- Thinking all polymers are synthetic
plastics – remember natural polymers are vital in biology.
- Confusing starch versus
cellulose: starch = α-glucose (energy storage), cellulose =
β-glucose (structural).
- Believing DNA is a protein – it’s a
nucleic acid polymer.
- Assuming rubber is fully synthetic –
natural rubber comes from latex (polyisoprene).
- Forgetting that silk/cotton are
natural fibres, not synthetic.
In summary:
Natural polymers are formed by condensation
polymerisation of biological monomers.
Their structures (amino acids, glucose,
nucleotides, isoprene) dictate properties like strength, elasticity, or
information storage, which in turn explain their uses.
Exams across all boards (AQA, Edexcel, OCR,
WJEC, CCEA, CIE) expect students to compare these polymers, link structure
to function, and avoid common misconceptions.
14-16
gcse organic chemistry, keywords and phrases: revision study notes for 14-16 school
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