Component 3.2 - Oxygen Dissociation Curves Flashcards
Describe the structure of haemoglobin
Each haemoglobin molecule contains 4 haem groups, each harm contains an ion of Fe2+.
How does oxygen bind to haemoglobin?
Each iron ion can bind to one oxygen molecule, so four oxygen molecules can bind to each haemoglobin molecule, carrying it is as oxyhaemoglobin
Describe cooperative binding and how it is useful
The first oxygen molecule is hard to bind and changed the shape of the haemoglobin molecule, making it easier for the second molecule to attach - this changes the shape again making it easier for the third oxygen molecule to attach. This allows haemoglobin to pick up oxygen very rapidly in the lungs.
How does haemoglobin associate readily with oxygen at the alveoli but dissociate with oxygen at the muscles?
It changes its affinity for the oxygen by changing its shape.
Describe a normal oxygen dissociation graph
The oxygen affinity of haemoglobin at high partial pressures of oxygen is high and oxyhaemoglobin does not release oxygen, but binds to it.
At low oxygen partial pressures the oxygen affinity of haemoglobin decreases and it dissociates from oxygen for aerobic respiration
Where does haemoglobin load oxygen and where does it unload oxygen?
(Loads ) In the lungs where the oxygen partial pressure is high and the haemoglobin has a high affinity for oxygen, so it becomes saturated.
(Unloads) At tissues where the oxygen partial pressure is low due to it being used up by respiration and haemoglobin has a low affinity for oxygen.
Describe the oxygen dissociation curve of fetal haemoglobin
The haemoglobin of a fetus must absorb oxygen from the maternal haemoglobin at the placenta.
Fetal haemoglobin has a higher affinity for oxygen than the mothers haemoglobin at the same partial pressure meaning it can get full saturation at a lower partial pressure (living in lower oxygen environment)
This causes the percentage saturation of the fetus’s blood to be higher than its mothers (oxygen moves into blood of fetus)
Oxygen dissociation curve moves to the left
Describe the oxygen dissociation curve of an animal in a low-oxygen partial pressure environment e.g Lugworm
The oxygen dissociation curve will be to the left of a humans.
This means it’s haemoglobin has a higher affinity for oxygen at all partial pressures
Haemoglobin can become saturated at lower oxygen partial pressure
Higher percentage saturation at all partial pressures
What is a disadvantage of having an oxygen dissociation curve further to the left?
Haemoglobin cannot release oxygen as quickly.
Describe how carbon dioxide concentration effects the oxygen dissociation curve
If carbon dioxide concentration increases (e.g during exercise) haemoglobin releases oxygen more readily at any oxygen partial pressure.
Haemoglobin is less saturated with oxygen
Curve moves to the right - The Bohr effect
What is a solution to the problem of low oxygen availability which occurs in people who live at high altitudes?
They make more red blood cells, allowing more oxygen to be carried around the body to respiring muscles.
Describe the oxygen dissociation curve of an animal with a higher metabolic rate e.g a mouse
Their haemoglobin will have a lower affinity for oxygen at reduced partial pressures because more carbon dioxide is being produced
Haemoglobin can unload oxygen more quickly at higher oxygen partial pressures]
What is a disadvantage of having a dissociation curve to the left?
Harder to unload O2
