Exchange and Mass Transport - Haemoglobin Flashcards
What are the adaptations of red blood cells?
biconcave shape maximises surface area
small + flexible - can pass through small capillaries
no nucleus so more room to carry respiratory gases
packed with haemoglobin
What is haemoglobin made of?
4 polypeptide chains
4 iron ions (prosthetic group / haem group)
What is oxyhaemoglobin?
the oxygenated form of haemoglobin
What is the process of oxygen moving from the lungs to respiring tissues?
in the lungs, oxygen diffuses into plasma and into red blood cells
oxygen binds to haem group to maintain the concentration gradient of oxygen from alveoli to red blood cells
in respiring tissue, the oxygen dissociates from oxyhaemoglobin and diffuses into the respiring cells
What is pO2 / partial pressure / oxygen tension?
the amount of oxygen in a tissue
What is pO2 measured in?
kPa
How does ventilation of the lungs affect pO2?
it allows the lung tissue to have a higher pO2
What is the pO2 in respiring tissue?
Low due to the oxygen being used up in respiration
When the pO2 is high, what happens to the haemoglobin?
more oxygen will associate with it to form oxyhaemoglobin
Where is the % of haemoglobin saturation highest?
where the pO2 is high
What shape is the graph of pO2 (x-axis) against % saturation of haemoglobin (y-axis)?
S shaped:
What happens to the shape of haemoglobin after the first oxygen binds to a haem group?
the shape changes to present 2 of the 3 remaining haem groups
Why is it hard for all 4 haem groups to bind to oxygen at the same time?
the probability of an oxygen molecule hitting the fourth site is lower and so decreasing the affinity of the haem group
Why is the affinity of haemoglobin for oxygen higher in foetuses than adults?
because as foetuses can’t breathe, they need to obtain oxygen from the mother’s bloodstream
to do this, the haeoglobin needs to have a higher affinity to create a concentration gradient to allow oxygen to diffuse across
What are the 3 ways that CO2 is transported through the circulatory system?
dissolved in plasma (5%)
associates to form carbaminohaemoglobin (10%)
transported as H2CO3 ions dissolved in H2O (85%)
