Lec 5 - Oxygen in the Blood Flashcards
What is the solubility factor of oxygen in water?
The solubility factor for O2= 0.01 mmol.l -1. kPa-1.
What is T state of haemoglobin?
Low affinity for oxygen in T state (tense)
—> In this state it is difficult for oxygen to bind.
What is R state of haemoglobin?
High affinity for oxygen in R state ( relaxed)
—> In this state it is easier for oxygen to bind.
When is haemoglobin in the T state?
it is in the T state when the partial pressure of Oxygen is low.
What is the oxygen content like in anaemic patients with good functioning lungs?
-If the patient’s lungs are functioning okay, but they are anaemic, the pO2 will be normal but the oxygen content will be lower because there is less Hb present.
What is the normal Hb concentration?
It is approx 2.2 mmol.l-1.
Link capillary density to pO2.
- The higher the capillary density, the lower the pO2 can fall.
- —> This is because it doesn’t have so far to diffuse.
- ——–> very metabolically active tissue will have a higher capillary density such as heart muscle.
What does the Bohr shift do?
- pH effects the affinity of haemoglobin.
- Acidic conditions shift the dissociation curve to the right, so lower affinity for O2 at higher pO2 values.
What state is promoted at different pH?
- low pH promotes T-state of Hb (tense state)
- High pH (alkaline) promotes R-state.
How does temperature in the tissues shift the dissociation curve?
- Increased temperature shifts it to the right.
- metabolically active tissues have slightly higher temperature so extra O2 is given up.
- This causes Hb to go into the tense state (T)
What is the maximum unloading of oxygen?
- Maximum unloading occurs in tissues where pO2 can fall to a low level.
- maximum unloading also happens in conditions where increased metabolic activity result in more acidic environment and higher temperature.
- under these conditions about 70% bound oxygen can be given up.
What does 2,3 - Bisphosphoglycerate do?
- 2,3-BPG levels increase with anaemia or at altitude.
- Increased 2,3-BPG shifts the Hb dissociation curve for O2 to the right.
- It allows more O2 to be given up to tissues because of shift in curve.
When does 2,3-BPG levels drop?
They drop in stored blood due to refrigeration.
- 2,3-BPG enzyme stops working and this limits how much O2 can be given up at tissues.
What does carbon monoxide poisoning do to Hb?
- Carbon monoxide reacts with Hb to form COHb.
- It increases the affinity of unaffected subunits for O2.
- Therefore won’t give up O2 at the tissues.
- Fatal if HbCO is greater than 50%.
What is hypoxemia?
This is when there is a low pO2 in arterial blood.
