Protein with a quaternary structure made up of four polypeptide chains, each with a haem group containing an iron ion. Responsible for oxygen transport in red blood cells of mammals, birds and fish.
Deoxygenated blood contains haemoglobin
Oxygenated blood contains haemoglobin
Haemoglobin
Found in red blood cells
In the blood of mammals, birds and fish
A group of chemically similar molecules
Quaternary protein
Has 4 polypeptide chains associated together
Oxygen loading/associating with haemoglobin
Oxygen loads to/associates with haemoglobin to form oxyhaemoglobin
Cooperative nature of oxygen binding
First O2 molecule binds and causes a change in shape of Hb which makes it easier for the other O2 molecules to bind
How readily haemoglobin loads/associates with oxygen is called its affinity for oxygen
Haemoglobin's affinity for oxygen changes as the oxygen's concentration varies through the body
Affinity for oxygen
How readily haemoglobin loads/associates with oxygen
At the gas exchange surface
Partial pressure of O2 (ppO2) is high, so Hb has a high affinity for oxygen and loads readily
At the tissues
Partial pressure of O2 (ppO2) is lower, so Hb has a lower affinity for oxygen and unloads readily
Haemoglobin changes its affinity for oxygen under different conditions
Affinity
Ability to load/bind with oxygen
High affinity for oxygen
Oxygen loads to Hb
Low affinity for oxygen
Oxygen unloads from Hb
Oxygen dissociation curve
At the gas exchange surface, high ppO2 means Hb has high affinity so loads readily, resulting in high % saturation
At the tissues, lower ppO2 means Hb has lower affinity so unloads readily, resulting in lower % saturation
Increase in ppCO2
Causes the oxygen dissociation curve to shift right (Bohr shift), reducing Hb's affinity for oxygen
Higher ppCO2
At the same ppO2, the % saturation of Hb is lower, so more O2 is unloaded to cells
Different haemoglobins
Have different affinities for oxygen
High affinity haemoglobins load oxygen readily
Low affinity haemoglobins unload oxygen readily
Low oxygen environments
Hb has a higher affinity for O2, so loads more readily at the lower ppO2 available
Hb with high affinity for oxygen
Oxygen dissociation curve lies to the left
Fully loads at lower ppO2
Steeper curve ensures only small drop in ppO2 gives large drop in % saturation to dissociate oxygen to respiring cells
Hb with low affinity for oxygen
Oxygen dissociation curve lies to the right
Necessary for organisms with high oxygen demand and high rate of respiration
Curve to the left
Loads oxygen readily
Curve to the right
Releases (unloads) oxygenreadily
The animal's haemoglobin has the affinity for oxygen, not the animal itself
Haemoglobin
Has 4 haem groups, each one has an iron ion in the centre
One oxygen molecule can bind to one haem group so a total of 4 oxygen molecules can be carried by one Hb
When oxygen is bound to Hb it is called oxyhaemoglobin
Describe how oxygen loads
At the GE surface the partial pressure of oxygen is high
oxygen diffuses down a conc. gradient from alveoli into the red blood cells
Haemoglobin has a high affinity for oxygen due to a high partial pressure of oxygen
Therefore it loads/associates with oxygen readily (cooperative nature etc)
Red blood cells travel in the blood-mass transport-to tissues
Describe how oxygen is unloaded
At the tissues the partial pressure of oxygen is lower (as the O2 is used in respiration)
Haemoglobin has a lower affinity for oxygen due to lower partial pressure of oxygen
Therefore it unloads/disassociates oxygen
Oxygen diffuses down a conc. gradient from the red blood cells to the tissues
Haemoglobins affinity for O2 changes under different conditions
Lungs- (ppO2)=high THEREFORE Hb's affinity for O2= high Result=O2 loads to haemoglobin
Respiring tissues-(ppO2)=low THEREFORE Hb's affinity for O2 is low Results= O2 unloads from the haemoglobin
What is the affinity?
The ability to load/bind with oxygen
The change in Hb’s affinity for oxygen at different partial pressures of oxygen
Change in Hb’s affinity for oxygen at different partial pressures of oxygen
Influence of CO2 (ppCO2) on the dissociated of O2 from Hb
How ppCO2 influences oxygen dissociation from Hb
For the influence on oxygen dissociation from Hb what would happen if the pCO2 was high? How much saturation? Load or unload? and what would happen if pCO2 was low?
High pCO2=lower % saturation of haemoglobin so unloads more readily
Low pCO2=higher % saturation of haemoglobin so loads readily
Haemoglobins have different affinities for oxygen
High affinity= Loads/associates with oxygen readily
Low affinity= Unloads/dissociates from oxygen readily
In low oxygen environments
Hb has a high affinity for O2
So, loads more readily at the lower ppO2 available So what would the graph look like?
Needs Hb with a higher affinity for O2 so will load more readily at the lower ppO2 available
O2 dissociation curve lies to the left
Low oxygen environments need Hb with a higher affinity for oxygen so will load more readily at the lower ppO2 available
Why do some animals require a high rate of respiration?
Large SA:V
They are active (more energy required for movement etc)
Large S:A or very active animals have a high rate of aerobic respiration so, need Hb with a lower affinity for oxygen so it will unload more readily
Organisms that need haemoglobin with a low affinity for oxygen
ACTIVE ANIMALS
high rate of respiration=high demand for O2 release= O2 unloads readily from Hb
LARGE SA:V
loses more heat so higher rate of respiration to maintain body temp, so higher demand for O2 release=unloads CO2 readily