Gas exchange - the oxygen dissociation curve Flashcards
What does the oxygen dissociation curve show?
The rate at which oxygen associates and dissociates with haemoglobin at different partial pressures of oxygen (pO2)
The curve illustrates the relationship between pO2 and haemoglobin saturation.
What is partial pressure of oxygen?
The pressure exerted by oxygen within a mixture of gases; it is a measure of oxygen concentration
It indicates how much oxygen is available in the environment.
When is haemoglobin referred to as being saturated?
When all of its oxygen binding sites are taken up with oxygen; when it contains four oxygen molecules
This indicates a maximum capacity for oxygen transport.
How is the ease of haemoglobin binding and dissociating with oxygen described?
As its affinity for oxygen
A high affinity indicates easy binding and slow dissociation, while a low affinity indicates the opposite.
What happens when haemoglobin has a high affinity for oxygen?
It binds easily and dissociates slowly
This is crucial for effective oxygen uptake in the lungs.
What is expected in other liquids regarding oxygen association?
Oxygen would dissolve at a constant rate, providing a straight line on a graph
This contrasts with the variable rates of binding seen with haemoglobin.
What does the oxygen dissociation curve indicate when read from left to right?
The rate at which haemoglobin binds to oxygen at different partial pressures of oxygen
This is critical for understanding oxygen uptake in various tissues.
What occurs at low pO2 on the oxygen dissociation curve?
Oxygen binds slowly to haemoglobin, resulting in low saturation percentage
This limits haemoglobin’s ability to pick up oxygen in oxygen-depleted tissues.
What happens at medium pO2 on the curve?
Oxygen binds more easily to haemoglobin and saturation increases quickly
A small increase in pO2 leads to a large increase in saturation.
What is observed at high pO2 on the curve?
Oxygen binds easily to haemoglobin, resulting in high saturation percentage
Most binding sites are occupied, so further increases in pO2 have a smaller effect.
What information does the curve provide when read from right to left?
The rate at which haemoglobin dissociates with oxygen at different partial pressures of oxygen
This is important for understanding oxygen delivery to tissues.
What occurs in the lungs where pO2 is high?
There is very little dissociation of oxygen from haemoglobin
This supports efficient oxygen uptake in the lungs.
What is significant about the steep region of the curve at medium pO2?
Oxygen dissociates readily from haemoglobin, allowing for easy release to respiring tissues
This is crucial for cellular respiration.
What happens at low pO2 regarding dissociation?
Dissociation slows again as few oxygen molecules are left on the binding sites
The release of the final oxygen molecule becomes more difficult.
What explains the curved shape of the oxygen dissociation curve?
The shape of the haemoglobin molecule makes it difficult for the first oxygen molecule to bind
This results in a slow initial binding process.
What occurs after the first oxygen molecule binds to haemoglobin?
Haemoglobin changes shape, making it easier for the next oxygen molecules to bind
This is known as cooperative binding.
What happens as haemoglobin approaches saturation?
It takes longer for the fourth oxygen molecule to bind due to a shortage of remaining binding sites
This explains the levelling off of the curve.
