Maintaining a Balance Topic 9: Haemoglobin Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis There’s a lot of writing in this lecture however there are only 14 slides!

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 life- sustaining 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.