Transport in Animals - Transport of Carbon Dioxide and Fetal Haemoglobin Flashcards
how is around 5% of CO2 transported
dissolved in plasma
how is 10% of CO2 transported
combines directly with haemoglobin forming carbaminohaemoglobin
how is 85% of CO2 transported
diffuses into erythrocytes where the enzyme carbonic anhydrase catalyses the formation of carbonic acid from CO2 and water
what does carbonic acid dissociate into
H+ + HCO3-
describe the chloride shift
- the hydrogen carbonate ions diffuse out of the erythrocytes into the plasma.
- This causes chloride ions to enter the erythrocyte to balance the charge
describe the Bohr effect
- the H+ ions cause an increase in cell acidity
- haemoglobin acts as a buffer, taking up the H+ ions to form haemoglobinic acid
- this reduces the affinity of Hb for oxygen, so oxyhaemoglobin releases its oxygen
how does a faster rate of respiration affect the Bohr effect
the faster the rate of respiration, the higher the concentration of CO2 so more hydrogen ions are produced therefore more oxyhaemoglobin dissociates
describe the Bohr shift
- the formation of haemoglobinic acid means that when there is a higher pCO2 haemoglobin is less saturated with oxygen
- the dissociation curve shifts to the right
what is the effect of the Bohr shift
oxygen is more readily supplied to respiring tissues
where is myoglobin found
skeletal muscle
describe myoglobin
- has a similar structure and function to haemoglobin
- acts as an oxygen store in the muscle
describe the oxygen dissociation curve of myoglobin and why is it that way
lies to the left of that for haemoglobin (much steeper initially) so that it can bind to oxygen that haemoglobin is releasing
when will myoglobin release oxygen
will only release oxygen at very low pO2
how does a fetus obtain its oxygen
from its mother’s blood across the placenta
do fetal and mother’s blood mix
no, but vessels pass close enough to allow the diffusion of molecules from one to the other
describe the oxygen dissociation curve for fetal haemoglobin
lies to the left of that for adult haemoglobin
why is the oxygen dissociation curve for fetal haemoglobin to the left
- there is a lower partial pressure of oxygen in the placenta
- at this low pO2, fetal Hb has a higher affinity for oxygen than adult Hb
- this means oxygen dissociates from the adult Hb in the placenta and diffuses from the maternal blood to the fetal blood
- this increases the %saturation of fetal Hb with oxygen
what does the fetus use the oxygen for
aerobic respiration
