Adaptations for Transport GCE BIOLOGY BY2 Adaptations for Transport Next
The haem part of the molecule contains iron. Click on the magnifying glass to enlarge this image of the haemoglobin molecule + The haem part of the molecule contains iron. Each molecule has four haem groups and each one of these can bind with an oxygen molecule. Hb + 4O2 HbO8 Next
Oxygen Dissociation Curve Click the numbered sections on the graph for an explanation of what happens at each stage Oxygen Dissociation Curve Saturation of Haemoglobin / % Partial Pressure of Oxygen/ kPa 2 4 6 8 10 12 20 40 60 80 100 5 4 ? 3 Haemoglobin’s properties allow it to bind with a lot of oxygen at a high partial pressure of oxygen, but at low partial pressure, only a limited amount binds to it. Under conditions of a lack of oxygen (low partial pressure of oxygen), the haemoglobin yields its oxygen to the respiring cells – we refer to this as dissociation. The red blood cells transport the oxygen to respiring tissues. The partial pressure of oxygen in these tissues is low, as the oxygen is being used for respiration. The partial pressure of oxygen is high and the haemoglobin reaches saturation. The red blood cells collect oxygen in the capillaries surrounding the lungs. Show/ hide titles Show/ hide scale 2 Show/ hide line 1 Next ?
O2 O2 Haemoglobin This diagram shows how a model of haemoglobin reaches saturation with oxygen. haemoglobin The molecule is now saturated. Back O2 O2
HIGHER PRESSURE (kPa) Click on the above boxes to see movement of the molecules. The oxygen partial pressure (pO2) is a measure of oxygen concentration. The higher the concentration of dissolved oxygen, the higher the pressure. Back
Oxygen Dissociation Curve 100 80 60 Saturation of Haemoglobin / % 40 Samples of haemoglobin can be placed in different partial pressures of oxygen, before estimating how much of it becomes bound to the oxygen. We can plot the percentage saturation against the partial pressure to get an oxygen dissociation curve. 20 Show/ hide line 2 4 6 8 10 12 Next Partial Pressure of Oxygen/ kPa
Incorrect Correct The haemoglobin is almost saturated at a high partial pressure of oxygen A molecule of haemoglobin can carry seven molecules of oxygen at most Oxyhaemoglobin dissociates at a low partial pressure of oxygen The group haem contains iron Respiring tissues have a high partial pressure of oxygen Next
Note that each haemoglobin molecule contains four haem groups Why is an Oxygen Dissociation Curve S-shaped? Hint Answer 100 80 60 Note that each haemoglobin molecule contains four haem groups Saturation of Haemoglobin / % 40 When the first oxygen molecules binds to the first haem group, the haemoglobin molecule loses its shape. This makes it easier for the three other molecules to combine with the remaining haem groups. 20 2 4 6 8 10 12 Next Partial Pressure of Oxygen/ kPa
The Effect of CO2 on the Oxygen Dissociation Curve How much oxygen is transported by a molecule of haemoglobin also depends on partial pressure of carbon dioxide. 2 4 6 8 10 12 20 40 60 80 100 Show hide CO2 line CO2 Saturation of Haemoglobin / % From the graph we see that at high partial pressures of carbon dioxide, the oxygen dissociation curve shifts to the right. This is called Bohr’s shift. Higher partial pressure of carbon dioxide increases the dissociation of oxyhaemoglobin. Next Partial Pressure of Oxygen/ kPa
The Effect of CO2 on the Oxygen Dissociation Curve What is the significance of this in the body? Answer 2 4 6 8 10 12 20 40 60 80 100 CO2 Saturation of Haemoglobin / % When oxyhaemoglobin reaches the tissues, the high partial pressure of carbon dioxide from respiration causes oxyhaemoglobin to release its oxygen more easily. So oxygen is released where it’s needed. Next Partial Pressure of Oxygen/ kPa
The Effect of pH on the Oxygen Dissociation Curve 2 4 6 8 10 12 20 40 60 80 100 pH CO2 Saturation of Haemoglobin / % Show/ hide the pH curve Show/ hide the CO2 curve Next Partial Pressure of Oxygen/ kPa
Explain what you see here (Keep in mind what you’ve already seen) HINTS What happens to the level of CO2 in the water? What has happened to reduce the pH of the water? pH What does the pH meter show? What has happened to the level of oxygen in the water? Next
Discuss each image in turn – what do they have to do with oxygen dissociation? Next
The Oxygen Dissociation Curve of an Athlete in Training 2 4 6 8 10 12 20 40 60 80 100 The further left the curve shifts, the easier it is for haemoglobin to pick up oxygen. Saturation of Haemoglobin / % The further the oxygen dissociation curve shifts to the right, the easier it is for the haemoglobin to give up its oxygen. Next Partial Pressure of Oxygen/ kPa
Haemoglobin Myoglobin O2 O2 Found in the blood. It joins to 4 molecules of oxygen at its maximum saturation but low affinity compared to myoglobin. The haemoglobin never reaches 100% oxygen saturation Found in tissues. It binds to only one molecule of oxygen but there is greater affinity to oxygen. 3. The myoglobin can reach 100% oxygen saturation. Next
Oxygen Dissociation Curve for MYOGLOBIN 2 4 6 8 10 12 20 40 60 80 100 Myoglobin Myoglobin is a molecule in muscles that combines with oxygen. The oxygen dissociation curve for myoglobin is far to the left of haemoglobin. What does this mean? When is a person likely to obtain oxygen from the dissociation of oxyhaemoglobin? Saturation of Haemoglobin / % Haemoglobin Next Partial Pressure of Oxygen/ kPa
Foetus What is the function of the placenta? Answer placenta The blood of the foetus and the mother flows closely together, but never mixes. This allows substances like oxygen to diffuse into the blood of the developing foetus. Next
Oxygen Dissociation Curve for a Foetus 2 4 6 8 10 12 20 40 60 80 100 Foetal haemoglobin We see form this graph of oxygen dissociation that foetus haemoglobin binds more easily to oxygen than the mother’s haemoglobin. Why is this higher affinity advantageous to the foetus? Is there a disadvantage to the mother? Saturation of Haemoglobin / % Mother’s haemoglobin Show/ hide line Partial Pressure of Oxygen/ kPa