Oxygen - Haemoglobin dissociation Flashcards
What is the oxygen haemoglobin dissociation curve?
A curve that shows the proportion of oxygen saturated haemoglobin against the partial pressure of the oxygen
Why does the oxygen haemoglobin dissociation curve have a sigmoidal shape?
It is easier for haemoglobin to bind oxygen when there is already one oxygen bound (due to a conformational change in the molecule)
What is the p50 value that is sometimes seen on the curve?
The partial pressure of oxygen at which the red blood cells are 50% saturated with oxygen
What does it mean if the oxygen dissociation curve is shifted to the right?
Decreased oxygen affinity of haemoglobin and therefore more oxygen availability to the tissues
How many polypeptide chains make up haemoglobin?
4
How many oxygen molecules can each haemoglobin molecule hold?
4
What is meant by a high affinity?
When oxygen can bind easily to the haemoglobin but struggles to be released into the tissues
What is meant by low affinity?
Oxygen struggles to bind to haemoglobin but can easily be released to the tissues
In the alveoli of the lungs the partial pressure of oxygen is high. What does this mean about the oxygen binding?
Oxygen binds readily and is not easily released.
What does the curve flatten out at the hight levels of partial oxygen pressure (ie above 60mmHg)
There is very limited additional binding that can occur beyond this point.
In what situations would the curve be shifted to the right?
This indicates that the haemoglobin has a reduced affinity for oxygen and therefore can release it easily. This happens in situations where it it most needed such as exercise or haemmorhagic shock
List all the caused of right shift (use the pneumonic CADET)
C02 Acid 2-3DPG Exercise Temperature
If the patient is acidotic which way will the oxygen dissociation curve shift?
To the right
