Dissociation of oxyhaemoglobin (OCR A-level PE)

This detailed lesson describes how oxygen is transported by haemoglobin and explains how the dissociation of oxyhaemoglobin changes with increases in carbon dioxide (Bohr shift). The informative PowerPoint and accompanying resources have been designed to cover the final point of the cardiovascular and respiratory systems section of the OCR A-level PE specification.

The lesson begins by using a quiz round from the game show POINTLESS to engage students and to introduce haemotology as the study of diseases related to blood. This includes haemoglobin and students will be reminded that this is the protein that is found in the red blood cells of humans. They will learn that it is a protein consisting of four polypeptide chains with a haem group on each chain and that it is this haem molecule which has a high affinity for oxygen to enable oxyhaemoglobin to be formed. Moving forwards, students will plot an oxyhaemoglobin dissociation curve. The understanding of the changes in saturation can be poorly understood so a step-by-step method with simple questions to discuss is used to ensure that the fundamentals are embedded. Ultimately, students will understand that haemoglobin becomes fully saturated at the high partial pressures of oxygen at the alveoli at the lungs, before transporting it to the cells of the working muscles where it dissociates to release the oxygen at the lower partial pressures there.

A quick quiz competition, called SPORTS SCIENCE, is used to challenge their knowledge of the names of famous sports people to identify the surname of the scientist, Christian Bohr. They are told that this effect describes how an increase in the concentration of a substance affects the dissociation curve and are encouraged to predict what this substance might be. By shifting the curve to the right, students will learn that the affinity of haemoglobin is reduced. The curve is used to show how the saturation of haemoglobin is less at low partial pressures of oxygen when there is increased carbon dioxide concentration before they are challenged to summarise the effect on the dissociation before applying all of their knowledge to a final sporting situation.

The final task has been differentiated 2 ways so that students of differing abilities are able to access the work