Maternal and Fetal Haemoglobin

Could someone just explain the similarities/differences + any other information on this please? I just can't seem to get my head around this. [Syllabus]

Reply 1

Ramaya

LS.

Could someone just explain the similarities/differences + any other information on this please? I just can't seem to get my head around this. [Syllabus]

Fetal haemoglobin has a higher affinity for oxygen so that oxygen will pass from the maternal haemoglobin to the fetus. Diffusion alone will not provide the fetus with enough oxygen so it has fetal haemoglobin which will take the oxygen from the mothers blood. The dissociation curve for fetal haemoglobin shifts to the left of the mothers.

Reply 2

LS.

I still don't fully understand it... I don't get why I find this hard, I understood everything else in the section :confused:

I think this will have to be one of these things were I 'learn' answers to possible questions, without actually understanding what I'm writing.

But thanks for trying :smile:

Reply 3

Ramaya

LS.

I still don't fully understand it... I don't get why I find this hard, I understood everything else in the section :confused:

I think this will have to be one of these things were I 'learn' answers to possible questions, without actually understanding what I'm writing.

But thanks for trying :smile:

Yeh theres not that much actual information anywhere on it. Its not a major part of my syllabus, but i know we are doing different syllabuses. Just hope it doesn't come up!

Reply 4

cipapfatso

fetal haemoglobin consists of two alpha and two gamma polypeptide chains unlike adult haemoglobin which consists of two alpha and two beta polypeptide chains.

Thsi enables fetal haemoglobin to have a higher affinity for oxygen in order to "steal" oxygen from the mother's blood. Remember the atmosphere is roughly 20% oxygen. When the mother inhales she therefore take in an atmosphere containing 20% oxygen yet when the mother exhales it is only 16% oxygen. Therefore the level of oxygen in the mother's blood (lets assume 4% of that in the atmosphere) will be at lower partial pressures than the oxygen in the atmosphere, so in order to survive the fetus needs an advantage to steal oxygen.

Although all you'd have to say is [oxygen] in atmosphere > [oxygen in mother's blood] hence fetal haemoglobin must have an adaptation offering a greater affinity for oxygen. Personally i wouldn't bother quoting any % of gases in the atmosphere :smile:

Reply 5

Make sure you mention that as the maternal oxyhaemglo. dissociates, the foetal haemglo. is fully saturated.

Reply 6

Unregistered

this is basically just another way of saying what has already been said, but it helps me to think of it like this:

Imagine the graph in front of you. Pick a random low-ish pp. of oxygen. You should see that a higher % of maternal haemoglobin has dissociated from oxygen at this pp, and a lower % of foetal Hb.

Hence, the foetal Hb takes up the oxygen that the maternal Hb has just released.

dont know if that helps at all..

Reply 7

Unregistered

2776

Make sure you mention that as the maternal oxyhaemglo. dissociates, the foetal haemglo. is fully saturated.

Surely that's not necessarily true?

If you look at the curve for foetal Hb, even at relatively high pps of oxygen, the foetal curve is not at 100% saturation.