Draw and label the structure of an
amino acid.
Objectives
Outcomes
Outline the structures of proteins.
3: Represent the 4 structures of
proteins.
5: Explain the structures of proteins.
7: Analyse the importance of the
structures of proteins in biology.
Key terms: protein, primary, secondary, tertiary, quaternary.
Outcomes
3: Represent the
4 structures of
proteins.
5: Explain the
structures of
proteins.
7: Analyse the
importance of
the structures of
proteins in
biology.
Key terms: hydrolysis, amino acid, peptide linkage, primary, secondary,
tertiary, quaternary
Task
Outcomes
Based on your knowledge of how
other biological molecules have
undergone condensation
reactions draw two amino acids
bonded together.
3: Represent the 4 structures of
proteins.
5: Explain the structures of proteins.
7: Analyse the importance of the
structures of proteins in biology.
Key terms: protein, primary, secondary, tertiary, quaternary.
Outcomes
3: Represent the
4 structures of
proteins.
5: Explain the
structures of
proteins.
7: Analyse the
importance of
the structures of
proteins in
biology.
Key terms: hydrolysis, amino acid, peptide linkage, primary, secondary,
tertiary, quaternary
Task
Outcomes
Setting up protein
chromatography
3: Represent the 4 structures of
proteins.
5: Explain the structures of proteins.
7: Analyse the importance of the
structures of proteins in biology.
Key terms: protein, primary, secondary, tertiary, quaternary.
Task
Outcomes
Use the resources available to
build up a sheet with models of
different protein structures.
3: Represent the 4 structures of
proteins.
Include types of bond,
interactions and examples of
each type.
5: Explain the structures of proteins.
7: Analyse the importance of the
structures of proteins in biology.
Key terms: protein, primary, secondary, tertiary, quaternary.
The 4 structures of proteins
Primary structure:
Long line of
amino acids
Secondary structure
• Form weak bonds
and twists to form a 3D
structure – alpha helix
Secondary structure
Secondary structure
• The amino acids in the primary structure can bond together
to form :
• a) An alpha helix
b) a beta pleat
• The bonds involved are hydrogen bonds
• Large proteins will have regions containing both structures
Tertiary structure
Tertiary structure
• Disulfide bond – fairly
strong.
• Ionic bonds – weaker than
above and formed
between carboxyl and
amino groups.
• Hydrogen bonds –
numerous – easily broken
Quaternary structure
• Number of
polypeptide chains in
tertiary structure.
• Non protein groups
too – like haem
(prosthetic groups)
Task
Outcomes
Model the structures of proteins.
Give examples and explain the
bonds present in each type of
structure.
3: Represent the 4 structures of
proteins.
5: Explain the structures of proteins.
7: Analyse the importance of the
structures of proteins in biology.
Key terms: protein, primary, secondary, tertiary, quaternary.
Protein structure
Bonds in proteins
The 3D shape of a protein is maintained by several types of bond, including:
hydrogen bonds:
involved in all levels of structure.
hydrophobic interactions:
between non-polar sections of
the protein.
disulfide bonds: one of the strongest
and most important type of bond in
proteins. Occur between two
cysteine amino acids.
Types of protein
There are two different types of protein and they
are different shapes. The shape of a protein
molecule is related to its function.
• Globular proteins – these are round, compact and
easily soluble so they can be transported in fluids.
Examples are haemoglobin and enzymes.
• Fibrous proteins – these are tough and ropeshaped. They tend to be found in connective
tissues such as tendons. Collagen is an example
of a fibrous protein.
Fibrous proteins
Fibrous proteins are formed from parallel polypeptide chains held together by
cross-links. These form long, rope-like fibres, with high tensile strength and are
generally insoluble in water.
collagen – the main component of
connective tissue such as
ligaments, tendons, cartilage.
keratin – the main component of
hard structures such as hair,
nails, claws and hooves.
silk – forms spiders’ webs and silkworms’ cocoons.
Globular proteins
Globular proteins usually have a spherical shape caused by tightly folded
polypeptide chains.
The chains are usually folded so that hydrophobic groups are on the inside, while
the hydrophilic groups are on the outside. This makes many globular proteins
soluble in water.
transport proteins – such as
haemoglobin, myoglobin and those
embedded in membranes.
enzymes – such as lipase and DNA
polymerase.
hormones – such as oestrogen and
insulin.
Protein bonds
The four structural levels in proteins are held together by
different bonds:
• Peptide bonds (primary)
• Hydrogen bonds (secondary and tertiary)
• Ionic bonds (tertiary)
• Disulphide bonds (tertiary)
• Hydrophobic and hydrophilic interactions (tertiary)
Quaternary structure depends on the tertiary structure of
the individual polypeptides, and so is influenced by all
these bond types.
Write about the following, in the
context of tertiary structure:
a)
b)
c)
d)
e)
Hydrogen bonds
Ionic bonds
Van der Waals
Disulphide bridges
Hydrophilic and hydrophobic
regions
Outcomes
3: Represent the 4 structures of
proteins.
5: Explain the structures of proteins.
7: Analyse the importance of the
structures of proteins in biology.
Key terms: protein, primary, secondary, tertiary, quaternary.
Task
Outcomes
Retrieve chromatography results.
3: Represent the 4 structures of
proteins.
5: Explain the structures of proteins.
7: Analyse the importance of the
structures of proteins in biology.
Key terms: protein, primary, secondary, tertiary, quaternary.
‘Outline the production of a
dipeptide by a condensation
reaction. Include the structure of
a generalized dipeptide in your
answer.’
(Total 5 marks)
Outcomes
3: Represent the 4 structures of
proteins.
5: Explain the structures of proteins.
7: Analyse the importance of the
structures of proteins in biology.
Key terms: protein, primary, secondary, tertiary, quaternary.
Outcomes
3: Represent the
4 structures of
proteins.
5: Explain the
structures of
proteins.
7: Analyse the
importance of
the structures of
proteins in
biology.
Key terms: hydrolysis, amino acid, peptide linkage, primary, secondary,
tertiary, quaternary