Help - Haemoglobin

Why is that that we lose our Fetal Haemoglobin as a child and develope ordinary haemoglobin, when fetal haemoglobin has a higher affinity for 02?

Reply 1

Hurricane_Herd

1

As a child you need more oxygen. Basically, it (fetal Haemoglobin) has a higher affinity for oxygen, so that it diffuses from the mothers blood, to the babies, and is less likely to diffuse back into the mothers blood. when youre out of the womb, you don't need that ability

Reply 2

tarka

9

if you only had fetal haemoglobin, oxygen remains bound to the haemoglobin even in low oxygen partial pressures such as in the muscles. If its not released it can't be used for respiration so you will get muscle fatique quicker. YOu would tire quickly during exercise

Reply 3

john171

OP

11

That's it? I thought there was a more complicated reason...

Reply 4

gyrase

3

john171

Why is that that we lose our Fetal Haemoglobin as a child and develope ordinary haemoglobin, when fetal haemoglobin has a higher affinity for 02?

The fetus does not recieve CO2 and so fetal haemo. has higher affinity for O2.
After the fetus matures, the lungs develop and O2 is taken in from air, and CO2 breathed out, the heamo. carrying-capacity is affected by production of CO2 due to respiration activity.

Reply 5

Revenged

15

Dev.420

The fetus does not recieve CO2 and so fetal haemo. has higher affinity for O2.
After the fetus matures, the lungs develop and O2 is taken in from air, and CO2 breathed out, the heamo. carrying-capacity is affected by production of CO2 due to respiration activity.

Err... no... Hurricane's reasoning is correct...

Fetal haemoglobin and normal haemoglobin are different proteins with different sub-units...

The expression of certain haemoglobin sub-units and the type of haemoglobin changes after birth because you don't need such a high affinity for O2 out of the womb...

All gas exchange occurs via the placenta... the lungs do not take part in gas exchange in the womb (for obvious reasons)!

The foetus does receive a small amount of C02, it's just that there the net CO2 movement is out of the foetus into the maternal blood... but anyway the PCO2 is higher in the womb than the maternal blood... otherwise CO2 would diffuse into the foetus...

Reply 6

tctc

im thinking the main reason would be that the mother and fetus would both have the same haemoglobin so there is noooot a higher affinity for the fetus to recive o2 than the mother so fetus would die from oxygen deficiency..