Mass Transport In Animals Flashcards
Describe the quaternary structure of haemoglobin
4 polypeptide chains linked together to form an almost spherical molecule
Each polypeptide is associated with a haem group which can combine with a molecule of oxygen.
As a result each haemoglobin molecule can carry 4 oxygen molecules
When an oxygen molecule joins to haemoglobin its called?
When an oxygen molecule leaves haemoglobin its called?
Association - this takes place in the lungs
Dissociation - this takes place in the tissues
What does affinity for oxygen mean?
The tendency a molecule has to bind with O2
What causes loading and unloading of oxygen?
Changes in partial pressures of oxygen - concentration
In areas where pO2 is high affinity is also high so O2 associates with haemoglobin
In areas where pO2 is low, affinity is also low so O2 dissociates with haemoglobin
What does a oxygen dissociation curve show?
Relationship between saturation of haemoglobin with O2 and partial pressure of O2
Why is an oxygen dissociation curve S shaped?
Initial shape of haemoglobin molecule makes it difficult for the first O2 to bind meaning initially the gradient is shallow.
When it does bind it changes the quaternary structure causing it to change shape. This makes it easier for the other oxygen molecules to bind.
It takes a smaller increase PO2 to bind the second O2 molecule - this is known as positive cooperativity
The gradient of the curve steepens
After the binding of the third molecule while theoretically its easier for the 4th to bind it is not the case because with the majority of the binding sites occupied it is less likely to bind so the gradient flattens again.
What’s the Bohr effect?
Haemoglobin has a reduced affinity for oxygen at high concentrations of CO2
As cells respire they produce CO2 and this increases PCO2.
Oxygen affinity is reduced at high PCO2 so here oxygen is unloaded.
As a result the dissociation curve shifts right
How and why does haemoglobin shape change?
At gas exchange areas oxygen affinity is extremely high and CO2 is unloaded.
Due to the low CO2 conc the pH is slightly raised.
This changes the shape of the haemoglobin enabling it to load oxygen readily and also ensures it doesn’t unload oxygen before it reaches the tissues
The opposite occurs at the tissues.
How does haemoglobin and dissociation curves change for organisms who live in low O2 environments?
Have haemoglobin with higher O2 affinity so its good at loading available oxygen
Low O2 = dissociation curve is to the left of a normal human one
How does haemoglobin and dissociation curves change for organisms who have high activity levels?
Have haemoglobin with a lower affinity to oxygen as they need to be able to readily unload the oxygen.
Dissociation curve shifts right
How does haemoglobin and dissociation curves change for organisms who are smaller?
Smaller organisms tend to have higher SA:V ratios and therefore lose heat quickly.
They therefore have a high metabolic rate to keep them warm so use much O2.
Their haemoglobin has a lower affinity for oxygen than human’s so it can be readily unloaded.
Dissociation curve shifts right
Why does blood pass through the heart twice?
As when blood goes through the lungs its pressure is reduced and therefore it must go back to the heart to boost its pressure before being circulated to the rest of the tissues.
Blood must be delivered quickly to meet the body’s high metabolic rate
What does systole mean?
Contraction
What does diastole mean?
Relaxation
How do different CO2 concentrations affect pH?
Low CO2 concentration = a slightly raised pH.
Higher pH changes haemoglobin shape to one that can load oxygen more easily.
Also increases affinity for O2 so its not released while being transported.
High CO2 concentrations mean a lowered pH.
Lower pH changes the shape so it can unload O2 easier
Lower pH leads to a lower O2 affinity
Describe the ma
