Haemoglobin ( 3 ) Flashcards
What happens to the affinity of oxygen in the presence of carbon dioxide ( bohr effect )?
- Haemoglobin will have a reduced affinity for oxygen in the presence of carbon dioxide
- Greater the concentration of carbon dioxide, the more readily the haemoglobin releases its oxygen
What is the affinity for oxygen at gas exchange surfaces and why?
- At gas exchange surfaces the concentration of carbon dioxide is low because it diffuses across the exchange surface and is excreted from the organism
- Affinity of haemoglobin for oxygen is increased, when coupled with the high concentration of oxygen in the lungs, means that oxygen is readily loaded by haemoglobin
- Reduced carbon dioxide concentration shifts the oxygen dissociation curve to the left
What is the concentration of carbon dioxide at gas exchange surfaces and why?
• At gas exchange surfaces the concentration of carbon dioxide is low because it diffuses across the exchange surface and is excreted from the organism
How is the affinity for oxygen affected at respiring tissues?
- Concentration of carbon dioxide is high
- Affinity of haemoglobin for oxygen is reduced
- With the low concentration of oxygen in muscles, oxygen is readily unloaded from haemoglobin into the muscle cells
- Increased carbon dioxide concentration shifts the oxygen dissociation curve to the right
What affect does carbon dioxide concentration have on haemoglobin and why?
- Greater the concentration of carbon dioxide, the more readily haemoglobin releases its oxygen
- Dissolved carbon dioxide is acidic, and low pH causes haemoglobin to change shape
What is the entire process of loading oxygen?
- At gas exchange surface carbon dioxide is constantly being removed
- pH is slightly raised due to the low concentration of carbon dioxide
- Higher pH changes the shape of haemoglobin into one that enables it to load oxygen readily
- Shape increases affinity of haemoglobin for oxygen, so it is not released while being transported in the blood to the tissues
- In the tissues carbon dioxide is produced by respiring cells
- Carbon dioxide is acidic in solution, so pH of blood within tissues is low
- lower pH changes shape of haemoglobin into one with a lower affinity for oxygen
- Haemoglobin releases oxygen into the respiring tissues
what is the purpose of haemoglobin’s transportation, loading and unloading of oxygen?
• Ensures that there is always sufficient oxygen for respiring tissues
How does a tissues activity levels affect oxygen received, and why?
• The more active a tissue, the more oxygen is unloaded.
This occurs because:
• Higher rates of respiration produce more carbon dioxide, which lowers pH
• The lower the pH the greater the haemoglobin shape change, the more readily oxygen is unloaded
• Thus more oxygen is available to the tissues for respiration
Where does haemoglobin become saturated with oxygen in humans?
As it passes through the lungs
Why is saturation of haemoglobin at atmospheric pressure 97%?
• Not all haemoglobin molecules are loaded with their maximum four oxygen molecules
Why does haemoglobin return to blood with 75% saturation?
• When reaching a respiring tissue, haemoglobin will only release one molecule of oxygen
However, if tissue is very active more oxygen molecules will be released
Why have animals evolved different types of haemoglobin?
• As adaptations to different environments and conditions, such as a species of animal that live in an environment with a lower partial pressure of oxygen have evolved haemoglobin that has a higher affinity for oxygen than animals that live where partial pressure of oxygen is higher
What happens to partial pressure of oxygen when cells respire?
- When cells respire they use up oxygen
- This will lower partial pressure of oxygen
- Red blood cells will deliver oxyhaemoglobin to unload oxygen
What does 100% saturation represent?
Every haemoglobin molecule is carrying maximum of 4 molecules of oxygen
What does 0% saturation represent?
None of the haemoglobin molecules are carrying any oxygen
