Haemoglobin Flashcards
Oxygen transport?
Hb + 4 oxygen Hb(oxygen)4
What is haemoglobin?
Haemoglobin carries oxygen, it picks it up and drops it off.
Structure of haemoglobin?
It’s made up of 4 polypeptide chains, each of the chains contain 1 haem group. Each haem group can combine with 1 oxygen molecule.
How does haemoglobin bind with oxygen?
Haemoglobin reversible binds with oxygen so it’s a good transporter of it. In order to associate (load) oxygen it has to bind easily therefore Hb has a high affinity for oxygen, it picks it up easily. In order to dissociate (unload) oxygen Hb also has a low affinity for oxygen to drop it off to respire get tissues. This happens via diffusion.
What happens to Hb at high carbon dioxide concentrations?
A high concentration of carbon dioxide at respire not tissues changes the pH of Hb which causes it to change shape, reducing the affinity for oxygen so releasing it.
Partial pressure of oxygen?
The partial pressure of oxygen PO2 is a measure of oxygen concentration. PO2 will be high in the lungs and lower in body tissues such as muscles.
What does Hb affinity for oxygen depend on?
Hb affinity for oxygen depends on PO2. Oxygen combines with Hb to form oxyhemoglobin in a high PO2, this is a high affinity. Oxyhemoglobin breaks down into Hb and oxygen in a lower PO2, this is a lower affinity.
Disassociation curves?
- The first molecule of oxygen combines with Hb and slightly distorts it. The joining the first one is quite slow.
- After the Hb has changed shape a little it become easier for the 2nd and 3rd oxygen to join it speeding it up.
- It flattens off at the top because the joining of the 4th oxygen is more difficult slowing it down.
What is high at the lungs?
Partial pressure of oxygen, Hb affinity for oxygen and Hb saturation.
What is low at the tissues?
Partial pressure of oxygen, Hb affinity for oxygen and Hb saturation.
what is PCO2?
the concentration of carbon dioxide.
The effect of PCO2?
PCO2 also effects the affinity Hb has for oxygen. Carbon dioxide levels are high at times of increase respiration hence a high PCO2 decrease Hb affinity causing oxygen to be unloaded more readily. This is known as the Bohr effect. When there is a high PCO2 the dissociation curves moves to the right. The Hb loses its oxygen more readily. This is good as the cells are respiring faster and they need more oxygen. This increase the rate of oxygen dissociation and the curve shifts to the right. This means the saturation of blood with oxygen at a give PO2 is lower because more oxygen is being released.
Different types of Hb?
Different Hb have different shapes so different affinities for oxygen. The different shape is due to the tertiary structure which is due to different amino acid sequences. Each organism has a different DNA code for Hb with the correct affinity.
High affinity for oxygen?
Some have a high affinity for oxygen, they take up Oxygen very easily but do not release it as readily. This is need in a low oxygen environment and those with a small SA:V ratio. Those with a high affinity for oxygen do not require a high oxygen environment.
(Lungworms)
Low affinity for oxygen?
Some have a low affinity for oxygen, they do not take up oxygen as easily but release it more readily. This is needed in a high oxygen environment and those with a large SA:V ratio. Those with a low affinity for oxygen require a higher oxygen environment.
(Birds and mice).
