Oxygen dissociation curve of haemoglobin.

1. Oxygen dissociation curve of haemoglobin. Objectives: -Understand what is shown by the oxygen dissociation curve. -Be able to describe and explain the significance of the S-shaped curve. -Understand the Bohr effect -Be able to interpret other oxygen dissociation curves.

2. Haemoglobin recap - protein molecule • contains 4 Fe2+ ions. Each of these is capable of binding to 1 molecule of O2. • Found in red blood cells. Remember that there will be many molecules of haem in one red blood cell. • Haemoglobin varies between species.

3. From the alveoli- oxygen diffuses into the blood and is then picked up by the haemoglobin the in the red blood cell. Into the cells- haemoglobin gives up the oxygen. It then diffuses from the blood into the tissue fluid and into the cell.

4. In body tissues. There is a ______ concentration of oxygen in body tissues = low partial pressure. Haemoglobin has a low % saturation. This means that _________ will dissociate from the ____________ and will enter the _______ % saturation of haemoglobin with oxygen In the lungs. There is a ______ concentration of oxygen in the lungs = high partial pressure. Haemoglobin has a high % saturation at this partial pressure. . This means that _________ will be picked up by the ____________ in order for it to be transported through the blood. Partial pressure of oxygen (ppO2)

5. At high/low partial pressures, the haemoglobin has a high/low affinity for oxygen. This means that haemoglobin picks up oxygen more easily/ gives oxygen up more easily The curve is shifted to the left/right.

6. Your tasks… • Start by answering questions on the Bohr shift (you need to know about this). Mark your own answers. If you do not understand look through your text book or ask me. When correct/understand move on to… • Foetal haemoglobin and myoglobin. When correct/understand move on to… • Llamas and mice

7. Bohr Shift 1. Blood in the lungs contains a lower concentration of carbon dioxide (the carbon dioxide has just diffused back into the alveoli). The curve shifts to the left and the haemoglobin has a higher affinity for oxygen. It is at full saturation at a lower partial pressures. The haemoglobin picks up oxygen from the alveoli. 2. Blood in the tissues contains a higher concentration of carbon dioxide (from respiring tissues). The curve shifts to the right and the haemoglobin has a lower affinity for oxygen. It lets go of the oxygen very easily. The haemoglobin gives up the oxygen to the respiring tissues.

8. Bohr shift. Questions In the body, where would you find a low concentration of carbon dioxide? What affect does a low concentration of CO2 have on haemoglobin's affinity for oxygen? What implication does this change in affinity have? Why is this beneficial? In the body, where would you find a high concentration of carbon dioxide? What affect does a high concentration of CO2 have on haemoglobin's affinity for oxygen? What implication does this change in affinity have? Why is this beneficial? Bohr shift. Answers In blood around the lungs (alveoli). Give the haemoglobin a higher affinity for oxygen. Oxygen is picked up by the haemoglobin from the lungs. It can then be transported to respiring tissues. In the blood surrounding respiring tissues. Lowers haemoglobins affinity for oxygen. Oxygen is given up by the haemoglobin. This is beneficial as it is given to the respiring tissues.

9. Foetal haemoglobin and myoglobin Foetal haemoglobin. The oxygen dissociation curve for foetal haemoglobin is shifted to the left. Explain why this is beneficial for the foetus. 2. Myoglobin is a protein that is used to store oxygen in muscle cells. Explain how the oxygen dissociation curve of myoglobin helps it to carry out its function.

10. Foetal haemoglobin and myoglobin.Answers Foetal haemoglobin. The oxygen dissociation curve for foetal haemoglobin is shifted to the left. Explain why this is beneficial for the foetus. Oxygen from the mothers blood diffuses into the foetus blood at the placenta. This means that there is a relatively low concentration of oxygen in the foetus blood. The curve of foetal haemoglobin is shifted to the left. Foetal haemoglobin has a higher affinity for oxygen at lower partial pressures. This means that it will pick up oxygen easily in the placenta. 2. Myoglobin is a protein that is used to store oxygen in muscle cells. Explain how the oxygen dissociation curve of myoglobin helps it to carry out its function. The curve of myoglobin is shifted greatly to the left. This means that it has a higher affinity for oxygen at lower partial pressures. This allows it to act as a store-it will only give up oxygen when the concentration in the muscle gets very low.

11. Llama Human Small mammals or birds Llamas and Mice % saturation of haemoglobin partial pressure of O2 (mmHg)

12. Llamas and Mice Questions • The oxygen dissociation curve of llama haemoglobin is shifted to the left. What does this tell you about the haemoglobins affinity for oxygen at lower partial pressures? • With this curve, where would you expect a llama to live (you may know this already) and why. • Small mammals and birds have a very high metabolic rate meaning that they respire very rapidly. How does the shift to the right help them with this? Llamas and Mice Answers • The haemoglobin has a higher affinity for oxygen at lower partial pressures. • The llama lives at high altitude where there is a lower availability of oxygen. This shift in the curve means that oxygen can be picked up more easily in the lungs. • Curve is shifted to the right. This means that haemoglobin has a lower affinity for oxygen and therefore gives up oxygen more easily to the surrounding tissues.