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Haemoglobin
Use the paper, scissors and glue provided to
build a model of a protein.
10 minutes!
Protein structure
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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.
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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.
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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.
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Haemoglobin
Haemoglobin is a protein making up 95% of the dry mass
of a red blood cell. It is the means of transport of oxygen
around the body.
Haemoglobin is made up of four polypeptide chains, each
bound to one haem group.
Each haem group can
combine with one oxygen
molecule, so that one
molecule of haemoglobin
can combine with a
maximum of four oxygen
molecules. This forms
oxyhaemoglobin.
polypeptide chain
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Independent learning
Try to complete tasks 1-3 on the sheet.
15 minutes
If you finish early, get a textbook and start
reading about oxygen dissociation curves.
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How is oxygen concentration measured?
Oxygen binds to haemoglobin when oxygen is at a high
concentration, and dissociates from haemoglobin when
oxygen is at a low concentration.
The concentration of a gas in a mixture of gases can be
quantified in terms of its partial pressure. This is the
amount of pressure exerted by the gas relative to the total
pressure exerted by all the gases in the mixture.
Partial pressure is measured
in kilopascals (kPa) and is
written as PO2, PCO2, etc.
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The oxygen dissociation curve
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Factors affecting oxygen dissociation
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Foetal haemoglobin
The red blood cells in the foetal bloodstream contain a special
form of haemoglobin known as foetal haemoglobin.
This helps maximize
oxygen uptake from
the mother’s blood
stream, which has
already lost some of its
oxygen by the time it
reaches the placenta.
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foetal haemoglobin
100
90
80
70
60
50
40
30
20
10
0
oxyhaemoglobin
(% saturation)
Foetal haemoglobin
has a higher affinity
for oxygen than adult
haemoglobin.
adult
haemoglobin
0
2
4
6
8
10
12 14
oxygen
partial pressure (kPa)
© Boardworks Ltd 2008
What is myoglobin?
Myoglobin is a molecule with a similar structure to
haemoglobin, but with only one haem group.
This means
oxymyoglobin will only
dissociate when
oxygen levels are low.
It is found in muscle
cells, where it acts as
an oxygen reserve.
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myoglobin
100
90
80
70
60
50
40
30
20
10
0
oxyhaemoglobin
(% saturation)
Myoglobin has a very
high affinity for
oxygen, even at very
low partial pressures.
haemoglobin
0
2
4
6
8
10
12 14
oxygen
partial pressure (kPa)
© Boardworks Ltd 2008