Haemoglobin Flashcards
What shape is a haemoglobin molecule?
Quaternary protein - 4 polypeptide chains
Protein
2 alpha and 2 beta sub units
Haem group contains iron (Fe)
What is the function of haemoglobin?
To carry oxygen
It has 4 haem units which allow it to do this
BUT the function can be divide into 2 more roles
What are the other 2 roles that the function of haemoglobin (carrying oxygen) can be divided into
1) lungs
2) Respiring cells
oxyhaemoglobin
haemoglobin + oxygen -> oxyhaemoglobin
Hb + 4O2
Hb (O2)4
Alveols > red blood cell >body organ
High levels > oxyhaemoglobin > low
of oxygen levels
of oxygen
High levels of O2 - loading
Low levels of O2 - unloading
What is partial pressure?
the pressure exerted by one gas within a mixture of gases
What is oxyhaemoglobin?
Haemoglobin bound to oxygen
What is oxygen dissociation
oxygen detached from haemoglobin
What is affinity
Attraction of haemoglobin for oxygen
What is % haemoglobin saturation
% of haemoglobin bound to oxygen
What is the partial pressure of oxygen
concentration of oxygen
What happens in the lungs?
Lungs have a high partial pressure of oxygen
So Hb has a higher affinity for oxygen
So more oxygen attaches to Hb
Why happens on the muscles ?
The muscles have a low partial pressure of oxygen (due to respiration)
So haemoglobin has a lower affinity for oxygen
So oxygen dissociates (detaches) from haemoglobin
What is the max number of oxygen molecules a haemoglobin molecule can carry
4
Partial pressure in a graph
Partial pressure is a measure of concentration of a gas
Higher conc of dissolved oxygen = higher partial pressure
What does the top of the curve mean in a pO2 pressure/% saturation of blood with oxygen graph
top = high pO2, high saturation, high affinity
= loading in lungs
What does the bottom of the curve mean in a pO2/ % saturation of blood with oxygen graph mean?
bottom = low pO2
low saturation
low affinity
—> unloading at cells
What is meant by the cooperative nature of oxygen binding
When one molecule of oxygen binds to haemoglobin, this increases the affinity of other haem units making it easier for more oxygen to bind
Describe the dissociation curve when oxygen in loaded in the lungs
High pO2
High affinity
High saturation of oxygen
Describe the dissociation curve when oxygen is loaded in the tissues
low affinity
low pO2
low saturation of oxygen
What factors affect the oxygen dissociation curve?
partial pressure of CO2
pH
Temperature
All of these are linked to respiration
When respiration increases:
More CO2 is produced
CO2 dissolves in plasma producing carbonic acid (lowers pH)
More heat is produced
Curve shifts to the right
What is the bohr effect
The increased dissociation of oxygen causes a shift in the oxyhaemoglobin
dissociation curve to the right
The shift means that oxygen will dissociate from haemoglobin at a lower pO2 than normal
what does the bohr effect do?
repairing cells produce CO2
- pH decreases
- changes shape of haemoglobin
- lowers affinity for oxygen
- more oxygen unloaded
- more oxygen available for respiring cells
Why is the dissociation curve moving to right useful?
Reduced affinity of haemoglobin for oxygen
so more oxygen is reading unloaded to respiring cells
