Download THE COLOUR OF BLOOD BLOOD TYPES THE SMELL OF BLOOD

THE CHEMISTRY OF BLOOD
Blood is a complex chemical mixture. The chemicals in it dictate its colour, and some also contribute to its characteristic, slightly metallic
odour. Here we take a look at some of these chemicals, as well as examining some of the differences that determine a person’s blood type.
THE COLOUR OF BLOOD
N
O2
O
OH
Blood type is determined by the presence of antigens.
Antigens are found on red blood cell surfaces; they can bind
to antibodies and stimulate an immune response. Antibodies
are proteins in blood plasma that help fight infection.
Haemoglobin is a protein found in
blood, built up of smaller sub-units
containing ‘haems’. These haems
contain iron, and their structure
gives our blood its red colour when
oxygenated. Deoxygenated blood is a
red colour – not blue!
N
Fe
N
BLOOD TYPES
N
O
OH
HAEM B
(oxygenated form)
Blood lost due to bleeding gradually
turns brown, as haemoglobin is oxidised
to methaemoglobin.
APPROXIMATE WORLDWIDE DISTRIBUTIONS OF BLOOD TYPES
Key
ANTIBODY
Usually only red blood cells are added in transfusions, so only blood antibodies of the person receiving blood are of concern.
TYPE A+
A+
THE SMELL OF BLOOD
ANTIGEN
31%
TYPE A-
A-
Rh
A
2.5%
A
TYPE AB+
5%
AB+
A
B
B
O
B+
TRANS-4,5-EPOXY-(E)-2-DECENAL
The compound that gives human blood its characteristic
metallic odour is trans-4,5-epoxy-(E)-2-decenal. The metallic
smell of metals and blood coming into contact with skin is
largely due to oct-1-en-3-one, produced due to the reaction
between oxidised skin lipids and the iron in haemoglobin.
C
15%
Rh
B
A
0.5%
AB-
B
A
B
Rh
TYPE B+
O
TYPE AB-
TYPE B-
1%
B-
B
TYPE O+
O+
A
42%
Rh
TYPE O-
3%
O-
A
A
B
B
The antibodies a blood type contains determines what
blood can be received in transfusions. Someone with blood
containing A antibodies cannot be given blood containing A
antigens. O can be given to all as it contain no A or B antigens.
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