Maintaining a Balance
Topic 9: Haemoglobin
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
DOT POINT
 Explain the adaptive advantages of haemoglobin
 Outline the need for oxygen in living cells and explain why
removal of carbon dioxide from cells is essential
The Structure of Haemoglobin
Haemoglobin is a protein made up of four polypeptide chains
(called globins) and each is bonded to a haem (iron containing)
group. Each haem is a red pigment molecule and the iron
necessary for haemoglobin formation is obtained from the diet.
extraordinarylight.blogspot.com
The Structure of Haemoglobin
Since small amounts of iron are lost from the body regularly in
waste products like urine and faeces, a regular supply of dietary
iron is necessary to maintain haemoglobin in red blood cells. A
lack of iron in the diet may lead to a condition known as anaemia,
where there are too few red blood cells or the blood cells that are
present are unable to carry sufficient oxygen.
drugline.org
The Adaptive Advantage
Haemoglobin has the adaptive advantage of being able to increase
the oxygen-carrying capacity of blood. Haemoglobin molecules
each contain four haem units, giving one haemoglobin molecule
the ability to bond with four oxygen molecules and so far more
oxygen can be carried in blood cells by haemoglobin (1000
million molecules of oxygen) than could be carried dissolved in
plasma.
hyperbaric-oxygen-info.com
The Adaptive Advantage
Haemoglobin has a further
adaptive advantage because its
ability to bind oxygen increases
once the first oxygen molecule
binds to it. The binding of each
oxygen molecule causes it to
change slightly in shape, making
it easier for every subsequent
oxygen molecule to bind to it.
science.cabot.ac.uk
The Adaptive Advantage
This increases the rate and efficiency of oxygen uptake. As a
result, a very small increase in the oxygen concentration in the
lungs can result in a large increase in the oxygen saturation of
blood. For example, during exercise, we breath more deeply and
rapidly, increasing the oxygen intake into the lungs and this
causes an increased uptake of oxygen by haemoglobin.
toptenplus.com
The Adaptive Advantage
Another adaptive advantage of haemoglobin is that its capacity to
release oxygen increases when carbon dioxide is present. It is
important for haemoglobin to combine with oxygen at
respiratory surfaces, but equally important for it to release the
oxygen.
web2.stmaryssen-h.schools.nsw.edu.au
The Adaptive Advantage
Metabolising cells release
carbon dioxide, which
combines with water to
form carbonic acid and this
lowers the pH.
Haemoglobin has the
adaptive advantage of a
reducing affinity for
oxygen at a lower pH and
so it releases the oxygen in
these tissues where it is
needed. This is known as
the Bohr Effect.
unm.edu
The Adaptive Advantage
In the tissues of the body, once the haemoglobin has released
oxygen, it has an increased ability to pick up carbon dioxide. In
the lungs, as haemoglobin binds to oxygen it releases the carbon
dioxide more easily.
wnthinktank.wordpress.com
The Adaptive Advantage
The fact that haemoglobin is
enclosed in a red blood cell is
also an advantage because if it
were simply dissolved in the
plasma, oxygen would upset
the osmotic balance of the
plasma.
beltina.org
Oxygen, CO₂ and Cell Function
Oxygen is necessary for cellular respiration, a process by which
cells obtain energy from glucose. Energy is needed for lifesustaining processes such as growth, repair of tissues, movement,
excretion and reproduction.
phschool.com
Oxygen, CO₂ and Cell Function
Although glucose and other food molecules are energy rich, the
energy stored in them must be converted into a form living cells
can use for metabolism. Oxygen combines with glucose in a
sequence of enzyme controlled steps during cellular respiration
to release chemical energy as ATP.
hyperphysics.phy-astr.gsu.edu
Oxygen, CO₂ and Cell Function
ATP is the form of chemical energy needed by living cells for
their metabolism. This is called the oxidation of glucose and it
takes place in all living cells.
163.16.28.248
Oxygen, CO₂ and Cell Function
Carbon dioxide is produced in cells as a waste product of
chemical respiration. It must be removed from cells to prevent a
change in pH in the cells, bloodstream and body.
pic2fly.com
Oxygen, CO₂ and Cell Function
When carbon dioxide reacts with water in cytoplasm of cells of
in the plasma of blood, it forms carbonic acid. A build-up of
carbonic acid is toxic as it lowers the pH of the cells and
bloodstream, affecting the homeostatic balance within an
organism.
bio1100.nicerweb.com
Oxygen, CO₂ and Cell Function
A low (acidic) pH would prevent enzymes from functioning
optimally and this affects cell functioning by reducing metabolic
efficiency in the body. Therefore the removal of carbon dioxide is
essential for the optimal functioning of enzymes.
cikgurozaini.blogspot.com
Activity/Homework
 Use ALARM to answer the following question:
-Explain why the presence of haemoglobin in the red blood
cells of mammals is an adaptive advantage.