GCE BIOLOGY BY 2 Oxygen Dissociation Curves GCE
GCE BIOLOGY BY 2 Oxygen Dissociation Curves GCE BIOLOGY BY 2 Adaptations for Transport Next
GCE BIOLOGY BY 2 Oxygen Dissociation Curves 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 + 4 O 2 Hb. O 8 Next
Click the numbered sections on the graph for an explanation of what happens at each stage Oxygen Dissociation Curve 100 5 4 ? 80 3 Saturation of Haemoglobin / % GCE BIOLOGY BY 2 Oxygen Dissociation Curves 60 40 Haemoglobin’s The Under redconditions blood cells properties oftransport a lack allow of oxygen the it to oxygen (low bind partial with to arespiring lot pressure of oxygen tissues. ofoxygen), at The a high the The partial pressure of ispartial high The red blood cells collect oxygen inis pressure haemoglobin partial pressure of oxygen yields of oxygen, in its these oxygen but tissues to at low and the haemoglobin reaches the capillaries the low, respiring partial as pressure, the cells oxygen –surrounding we only isrefer being a limited to used thislungs. as for saturation. respiration. dissociation. amount binds to it. 20 2 0 Show/ hide scale Show/ hide line 1 0 Show/ hide titles 2 4 6 Partial Pressure of Oxygen/ k. Pa 10 8 ? 12 Next
Haemoglobin This diagram shows how a model of haemoglobin reaches saturation with oxygen. GCE BIOLOGY BY 2 Oxygen Dissociation Curves haemoglobin The molecule is now saturated. Back
GCE BIOLOGY BY 2 Oxygen Dissociation Curves Click on the above boxes to see movement of the molecules. HIGHER PRESSURE (k. Pa) The oxygen partial pressure (p. O 2) is a measure of oxygen concentration. The higher the concentration of dissolved oxygen, the higher the pressure. Back
Oxygen Dissociation Curve 100 Saturation of Haemoglobin / % GCE BIOLOGY BY 2 Oxygen Dissociation Curves 80 60 40 Samples of haemoglobin can be placed in different partial pressures of oxygen, before estimating how much of it becomes bound to the oxygen. 20 We can plot the percentage saturation against the partial pressure to get an oxygen dissociation curve. Show/ hide line 0 0 2 4 6 Partial Pressure of Oxygen/ k. Pa 8 10 12 Next
GCE BIOLOGY BY 2 Oxygen Dissociation Curves Incorrect Correct The haemoglobin is almost saturated at a high partial pressure of oxygen A molecule of haemoglobin 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
Why is an Oxygen Dissociation Curve S-shaped? Hint Answer 100 Saturation of Haemoglobin / % GCE BIOLOGY BY 2 Oxygen Dissociation Curves 80 60 Note that each haemoglobin When the first oxygen molecules binds to the first haem group, the contains haemoglobin molecule loses its four shape. This makes it easierhaem for the three other groups 40 20 molecules to combine with the remaining haem groups. 0 0 2 4 6 8 Partial Pressure of Oxygen/ k. Pa 10 12 Next
The Effect of CO 2 on the Oxygen Dissociation Curve How much oxygen is transported by a molecule of haemoglobin also depends on partial pressure of carbon dioxide. 100 Show hide CO 2 line Saturation of Haemoglobin / % GCE BIOLOGY BY 2 Oxygen Dissociation Curves 80 CO 2 60 From the graph we see that at high partial pressures of carbon dioxide, the oxygen dissociation curve shifts to the right. 40 This is called Bohr’s shift. 20 Higher partial pressure of carbon dioxide increases the dissociation of oxyhaemoglobin. 0 0 2 4 6 8 Partial Pressure of Oxygen/ k. Pa 10 12 Next
The Effect of CO 2 on the Oxygen Dissociation Curve What is the significance of this in the body? Answer 100 Saturation of Haemoglobin / % GCE BIOLOGY BY 2 Oxygen Dissociation Curves 80 CO 2 60 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. 40 20 0 0 2 4 6 8 Partial Pressure of Oxygen/ k. Pa 10 12 Next
The Effect of p. H on the Oxygen Dissociation Curve 100 Saturation of Haemoglobin / % GCE BIOLOGY BY 2 Oxygen Dissociation Curves 80 p. H CO 2 60 40 20 Show/ hide the p. H curve Show/ hide the CO 2 curve 0 0 2 4 6 8 Partial Pressure of Oxygen/ k. Pa 10 12 Next
Explain what you see here HINTS (Keep in mind what you’ve already seen) What happens to the level of CO 2 in the water? GCE BIOLOGY BY 2 Oxygen Dissociation Curves p. H What has happened to reduce the p. H of the water? What does the p. H meter show? What has happened to the level of oxygen in the water? Next
GCE BIOLOGY BY 2 Oxygen Dissociation Curves Discuss each image in turn – what do they have to do with oxygen dissociation? Next
The Oxygen Dissociation Curve of an Athlete in Training 100 The further left the curve shifts, the easier it is for haemoglobin to pick up oxygen. Saturation of Haemoglobin / % GCE BIOLOGY BY 2 Oxygen Dissociation Curves 80 60 40 The further the oxygen dissociation curve shifts to the right, the easier it is for the haemoglobin to give up its oxygen. 20 0 0 2 4 6 Partial Pressure of Oxygen/ k. Pa 8 10 12 Next
GCE BIOLOGY BY 2 Oxygen Dissociation Curves Haemoglobin Myoglobin 1. Found in the blood. 1. Found in tissues. 2. It joins to 4 molecules of oxygen at its maximum saturation but low affinity compared to myoglobin. 2. It binds to only one molecule of oxygen but there is greater affinity to oxygen. 3. The haemoglobin never reaches 100% oxygen saturation 3. The myoglobin can reach 100% oxygen saturation. Next
Oxygen Dissociation Curve for MYOGLOBIN 100 Myoglobin Saturation of Haemoglobin / % GCE BIOLOGY BY 2 Oxygen Dissociation Curves 80 Myoglobin is a molecule in muscles that combines with oxygen. The oxygen dissociation curve for myoglobin is far to the left of haemoglobin. 60 Haemoglobin 40 What does this mean? When is a person likely to obtain oxygen from the dissociation of oxyhaemoglobin? 20 0 0 2 4 6 Partial Pressure of Oxygen/ k. Pa 8 10 12 Next
GCE BIOLOGY BY 2 Oxygen Dissociation Curves Foetus Answer placenta What is the function of the 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 100 Foetal haemoglobin Saturation of Haemoglobin / % GCE BIOLOGY BY 2 Oxygen Dissociation Curves 80 60 We see form this graph of oxygen dissociation that foetus haemoglobin binds more easily to oxygen than the mother’s haemoglobin. 40 Why is this higher affinity advantageous to the foetus? 20 Mother’s haemoglobin 0 0 2 4 Is there a disadvantage to the mother? 6 Partial Pressure of Oxygen/ k. Pa 8 10 Show/ hide line 12
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