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What type of structure does Hb have?
Quaternary - 4 polypeptide chains
What is the role of Hb?
To transport oxygen around the body by loading and unloading it
What shape does a RBC have and why?
It has a biconcave shape to give it a larger SA:V so that oxygen can diffuse into the cell more rapidly
No nucleus so more space for Hb so more oxygen can be carried
What is each Hb composed of?
4 sub units each containing a Haem group at its centre
How many oxygen molecules can one haem group bind with?
4 as they have 4 haem groups that can each bond to 1 oxygen molecule
When is oxyhaemoglobin formed?
When Hb associates with oxygen in areas with a high ppO2
Oxyhaemoglobin disassociates with oxygen in an area with a lower ppO2
What is partial pressure?
The amount of a particular gas in a mixture of gases or a solution
What shape does an ODC have?
Sigmoid or S shaped
What is loading?
Oxygen is taken up by Hb
What is unloading?
When oxygen is given up by Hb
What is meant by affinity?
attraction
Why is oxygen taken up in the lungs?
there is a higher ppO2
Hb has a high affinity for oxygen
Oxygen loads more readily so there is a higher % saturation of haemoglobin
Why is oxygen unloaded at respiring tissues?
low ppO2
Hb has a low affinity for oxygen
Oxygen unloads more readily giving Hb a lower % saturation
Why does CO2 cause oxygen to unload at respiring cells?
CO2 dissolves in the blood which lowers the pH
pH changes away from the optimum for Hb
causes H/ ionic bonds in the tertiary to break
alters the shape of the binding sites
this causes oxygen to unload more readily
What is co operative binding?
The binding of one molecule of oxygen makes it easier for the second one to bind
How does co operative binding occur?
1st oxygen binds which causes a change in tertiary structure
allows more oxygen to bind more easily as it uncovers another active site with the Fe ion
Hb becomes more saturated
How is co operative binding shown on the ODC?
At low ppO2 there is little increase in saturation of Hb until the 1st oxygen molecule binds and then there is a rapid rise as it becomes easier for the oxygen to bind
What is the advantage of co-operative binding?
It allows for rapid loading of oxygen in the lungs and rapid unloading at respiring tissues
What is the bohr shift?
The effect of the increase in Co2 concentration of the disassociation of oxyhaemoglobin
What happens when the ODC is shifted to the right?
there’s a high ppCO2
ODC shifts to the RIGHT
Hb now has a reduced affinity for oxygen
more oxygen is unloaded
Higher respiration rates
examples are animals with high metabolic rate- very active or small and lose heat due to large SA:V
Why do different animals have different types of Hb?
They have an altered primary structure
What happens when the ODC is shifted to the left?
curve shifts to the left
Hb has a higher affinity for oxygen
becomes fully saturated at lower ppO2
examples are foetal hb, high altitudes
Note
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