Adaptations for Transport
GCE BIOLOGYBY2 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 + 4O 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 3 ? 2 A small change in partial pressure of oxygen results in a large change in percentage saturation. At high partial pressures of oxygen the Hb has a high percentage saturation and therefore has a high affinity for O2. At low partial pressures of Oxygen the Hb has a low percentage saturation and therefore has a low affinity for O2. Show/ hide titles Show/ hide scale 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 againstthe 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 haemgroups 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 Bohrs 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 its 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 youve 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% oxygensaturation 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 oxygento 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 mothers haemoglobin. Why is this higher affinity advantageous to the foetus? Is there a disadvantage to the mother? Saturation of Haemoglobin / % Mothers haemoglobin Show/ hide line Partial Pressure of Oxygen/ kPa