Haemoglobin Flashcards
What is haemoglobin?
Haemoglobin is a large protein with a quaternary structure - it is made up of four polypeptide chains. Each chain has a haem group, which contains an iron ion and give haemoglobin its red colour
Haemoglobin has a high what for oxygen
Haemoglobin has a high affinity for oxygen - each molecule can carry four oxygen molecules
What does oxygen join haemoglobin to form?
Oxyhaemoglobin
What is the partial pressure of oxygen?
The partial pressure of oxygen (pO2) is a measure of oxygen concentration. The greater the concentration of dissolved oxygen in cells, the higher the partial pressure
What is the partial pressure of carbon dioxide?
The partial pressure of carbon dioxide (pCO2) is a measure of the concentration of carbon dioxide in a cell
When does oxygen load and unload onto haemoglobin?
Oxygen loads onto haemoglobin to form oxyhemoglobin when there’s a high partial pressure of oxygen. Oxyhaemoglobin unloads its oxygen where there’s a lower partial pressure of oxygen
What does haemoglobin do when oxygen enters the lungs?
Oxygen enters the blood capillaries at the alveoli in the lungs. Alveoli have a high pO2 so oxygen loads onto haemoglobin to form oxyhaemoglobin. When cells respire, they use up oxygen - this lowers the pO2. red blood cells deliver oxyhaemoglobin to respiring tissues, where it unloads its oxygen. The haemoglobin then returns to the lungs to pick up more oxygen
What does a dissociation curve show?
A dissociation curve shows how saturated the haemoglobin is with oxygen at any given partial pressure
On a dissociation curve why would saturation of oxygen be high?
Where pO2 is high haemoglobin has a high affinity for oxygen - it will readily combine with oxygen, so has a high saturation of oxygen
On a dissociation curve why would saturation of oxygen be low?
Where pO2 is low haemoglobin has a low affinity for oxygen - it releases with oxygen rather than combining with it so it has a low saturation of oxygen
Why is a dissociation curve ‘S-shaped’
When haemoglobin (Hb) combines with the first oxygen molecule, its shape alters in a way that makes it easier for other molecules to join. But as the Hb starts to become saturated, it gets harder for oxygen molecules to join. As a result, the curve has a steep bit in the middle where it’s easy for O2 molecules to join, and a shallow bit at each end where it’s harder
Haemoglobin gives up oxygen more readily at high what?
Higher partial pressure of carbon dioxide
Explain the Bohr effect
When cells respire they produce carbon dioxide, which raises the pCO2. This increases the rate of oxygen unloading (the rate at which oxyhaemoglobin dissociates to form Hb and oxygen) so the dissociation curve shifts to the right. The saturation of blood with oxygen is lower for a given pO2, meaning more oxygen is being released
Different organisms have different types of haemoglobin with different what?
Oxygen transporting capacities
What is the haemoglobin like in organisms that live in an environment with a low concentration of oxygen
Organisms that live in environments with a low concentration of oxygen have haemoglobin with a higher affinity of oxygen than human haemoglobin - the dissociation curve is to the left of ours
